N. Villanueva
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N. Villanueva
TABLE OF CONTENTS
Intro to Para 3
PROTOZOANS
Pathogenic ameba 7
Dracunculus medinensis 65
Filarial worms 66
PHYLUM PLATYHELMINTHES: CLASS TREMATODA
Commensal ameba 9
Schistosoma spp. 72
Free-living ameba 12
Paragonimus westermani 77
Intestinal flagellates 15
Fasciolopsis buski 79
Urogenital flagellates 20
Echinostoma ilocanum 80
Ciliates 23
Heterophyid worms 81
Blastocystis hominis 24
Fasciola spp. 82
Malarial parasites 25
Clonorchis and Opisthorchis 84
Other protozoans 34
Dicrocoelium dendriticum 86
PHYLUM ASCHELMINTHES: CLASS NEMATODA
Ascaris lumbricoides 50
Eurytrema pancreaticum 87
PHYLUM PLATYHELMINTHES: CLASS CESTODA
Trichuris trichiura 52
Diphyllobothrium latum 92
Enterobius vermicularis 54
Taenia spp. 94
Hookworms 55
Hymenolepis spp. 97
Strongyloides stercoralis 58
Dipylidium caninum 99
Capillaria philippinensis 59
Raillietina garrisoni 100
Anisakiasis 61
Echinococcus spp. 101
Animal Ascarids 62
Multiceps multiceps 103
Parastrongylus cantonensis 62
Trichinella spiralis 64
Laboratory Diagnosis 105
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N. Villanueva
INTRO TO PARA: FUNDAMENTALS OF PARASITOLOGY
BIOLOGICAL RELATIONSHIPS
 Biological relationships
o Symbiosis: relationship between 2 unlike organisms
o Symbiont/Symbiote: the members of the symbiotic
relationship
o Examples of Symbiotic Relationships
 Mutualism: both benefit (Ex: termites and flagellates)
 Commensalism: one benefits, one is not
affected/unharmed (Ex: Entamoeba coli in the intestinal
lumen)
 Phoretic relationship: one that involves “Phoresis”
 Phoresis: means “to carry”
 The organism is carried and nothing else happens
 Phoront: organism being carried
 No physiologic interaction is involved between the
host and the phoront
 Ex: Cockroaches carrying Ascaris eggs
 Parasitism: one benefits (parasite) and one is harmed
(host)
 Ex: Entamoeba histolytica in humans
 Parasitology: an area of biology that deals with the
dependence of one organism on another
o Study of parasites, its hosts, and their relationships
 Characteristics of parasitic diseases
o Prevalence in developing countries and in lower
socioeconomic population
o Low mortality and morbidity (not deadly per se, usually
neglected, very few people die)
o Limited drug development
o No current vaccines
HOSTS
 Host: species which harbors the parasite
o May show no harmful effects
o May suffer from the pathogenic effects of the parasite
Final Host
Intermediate
Host
Vectors
Hosts
 Also known as Definitive Host
 Harbors the mature form of the parasite
 Sexual reproduction and maturity takes
places in these hosts
 Common FH are man
 Harbors immature/larval form of the
parasite
 Asexual reproduction takes place
 Ex: Lower animals, vegetation, insects,
sometimes humans (in Plasmodium
infections)
 Responsible for transmission
 Biologic Vector: there is morphologic
change or transformation of parasite
before transmission to another host
o Parasite is always inside
o Ex: Aedes, mosquitoes, Tsetse fly, ticks
 Mechanical/Phoretic Vector: no
morphologic change occurs
o Parasite always outside
Accidental
Host
Paratenic
Host
Dead-end
Host
Reservoir
Host
o Ex: Cockroaches and flies
 Host that harbors a parasite that usually
does not infect it
 Ex: Man infected with Toxocara canis
 Also known as Transfer Host
 Harbors parasites that do not develop to
further stages
 Only transfers from one host to another
 Widens parasite distribution and bridges
ecological gap between definitive and
intermediate hosts
 Ex: Boars for Paragonimus westermani
 Also known as Incidental Host
 Host that does not anymore allow the life
cycle of the parasite to continue
 Ex: Humans for Trichinella spiralis
 Host other than the parasite’s usual hosts
that allows the life cycle to continue
 Animals that can continue the life cycle
even in absence of humans
 Becomes additional sources of human
infection
 Examples
o Pigs for Balantidium coli
o Field rats for Paragonimus westermani
o Beavers for Giardia lamblia
o Cats for Brugia malayi
PARASITES
 Parasite that always requires a host
to survive
 Most parasites
 Ex: Ascaris, Hookworms, Trichuris,
Tapeworms
Facultative
 Has a free-living and parasitic
phase
 Free-living: phase found in the
environment
 When conditions are unfavorable,
enters the parasitic phase
 Ex: Threadworms
Commensal
 Non-pathogenic
 Does not cause disease
 Ex: Entamoeba coli
Parasites According to Habitat
Ectoparasite
 Parasite lives outside the host
 Infestation: presence of an
ectoparasite in a host
 Ex: Ticks, Lice, Fleas
Endoparasite
 Parasite lives inside the host
 Infection: presence of an
endoparasite in a host
 Most parasites
Erratic Parasite
 Parasite not living in its natural
habitat
 Ex: Ascaris (when it is not in the small
intestine)
Accidental
 Also known as an Incidental
Parasite
Parasite
Obligate
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 Parasite that does not live in its usual
host
Spurious
 Free-living organism that passes
Parasite
through the GI tract without infecting
the host
Temporary
 Transient parasites
Permanent
 Remains on host for its entire life
Parasites According to Egg Laying Capacity
Oviparous
 Lays immature eggs (eggs not yet
embryonated, egg has no larva yet)
 Ex: Ascaris, Trichuris
Ovoviviparous
 Lays mature eggs (embryonated,
larva present)
 Ex: Schistosoma, Clonorchis
Larviparous
 Larva-laying
 Ex: Trichinella
Parasites According to Sexes
Monoecious
 Also known as Hermaphrodites
 Both testes and ovaries found in one
parasite
 Ex: Flukes and Tapeworms
Dioecious
 Presence of separate sexes
 Female and male parasite
 Ex: Nematodes (except
Strongyloides)
Parthenogenetic  Females capable of self-fertilization
 Ex: Strongyloides stercoralis
Is
PARASITE STAGES
Adult
Larva
Egg/Ovum
Trophozoite
Cyst
Stages for Helminthes
Mature form
 Immature form
 Stages include L1-L3
 Nonmotile form
 Resistant stages
 Infective stage (for most parasites): stage
that once ingested, infects the host
Stages for Protozoans
 Motile/vegetative stage
 Nonmotile
 Usually the infective stage
TRANSMISSION
Soil Transmitted
Helminthes
(STH)
Vector Borne
Food Borne
 HATS
 Hookworms (Necator americanus
and Ancylostoma duodenale)
 Ascardis lumbricoides
 Trichuris trichiura
 Strongyloides stercoralis
 Mosquitoes and ticks (arthropods)
 Plasmodium, Hemoflagellates,
Filarial worms
 When you are fond of eating
different types of food
 Undercooked or raw food
 Fasciola, Opisthorchis, Clonorchis,
Echinostoma, Heterophes, Taenia
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Water Borne
Vertical
Transmission
Transmammary
Skin Penetration
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Inhalation
Intimate Contact
Drinking contaminated water
Giardia, Cryptosporidium
Congenital transmission
Toxoplasma gondii
Drinking of breast milk
Ancylostoma, Strongyloides
Exposure of skin to soil or water
Hookworms, Strongyloides,
Schistosoma
Of airborne eggs
Enterobius
Sexual contact
Trichomonas vaginalis
LIFE CYCLES
 Life cycles: how the parasite develops
 Can be direct or indirect
 Direct: no intermediate host, only consists of a parasite and
a final host
 Indirect: has an intermediate host
o Migration of larval stages present in some parasites
o Ex: Plasmodium
 Life cycle more complicated = lesser chances for parasite to
survive
EXPOSURE AND INFECTION
Disease
Pathogen
Infection
Carrier
Incubation
Period
Pre-patent
Period
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Exposure
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Autoinfection
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Superinfection 
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Presence of signs and symptoms
Any organism that causes disease
Not equal to disease
Establishment of an organism in one
host (with multiplication of organism)
No destruction of tissue yet
Harbors the organism, but person
shows no signs or symptoms
Also like a reservoir
Period between infection and
appearance of signs and symptoms
In this period, there are no symptoms
AKA: Clinical Incubation Period
Period between infection and
evidence/demonstration of infection
Positive lab result
Can be ahead of incubation period, or
lesser
AKA: Biologic Incubation Period
process of inoculating an infective
agent
infected individual becomes his/her
own source of infection
parasite does not need to go outside
body to replicate/multiply
Capillaria, Strongyloides, Enterobius,
Cryptosporidium, Hymenolepis nana
Also known as Hyperinfection
Infected individual is further infected
with the same parasite
Strongyloides
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EPIDEMIOLOGY
 Epidemiology: study of patterns, distribution, and occurrence
of disease
Prevalence
Cumulative
Prevalence
Incidence
Sporadic
Endemic
Epidemic
Pandemic
Eradication
Elimination
Morbidity
Mortality
Intensity of
Infection
 Number of patients infected at one point in
time
 Percentage of individuals in a population
infected with at least one parasite
 Number of new cases
 Measures risk of developing the disease
 Few cases
 Ongoing local transmission in one area
 Outbreak
 Sudden increase in number of cases
 Whole world
 Worldwide epidemic
 Permanent reduction to zero of worldwide
incidence of an infection
 Once achieved, continued efforts to reduce
infections no longer needed
 Reduction to zero of incidence of a
specified disease in an area
 Continued intervention is needed
 Number of cases
 Number of deaths
 Severity of the infection
 Ex: worm burden in Ascaris
EFFECTS OF PARASITE TO HOST
 May infect humans, but do not cause disease (commensals)
 Can cause injury by release of metabolites/enzymes
(Entamoeba histolytica)
 Can cause invasion and tissue destruction
 Can deprive certain nutrients from hosts (Diphyllobothrium
latum: deprives humans of Vitamin B12 or Cyanocobalamin)
 Tissue damage (Ex: fatty degeneration, albuminous
degeneration, necrosis)
 Tissue changes
o Hyperplasia: increase in number of cells
o Hypertrophy: increase in size of cells
o Metaplasia: change from one cell type to another
o Neoplasia: formation of tumors or neoplasms
 Streamlining: inability of parasite to synthesize certain
cellular components, so they need the help of the host to
obtain these components
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o High carbohydrates favors development of some
tapeworms
Natural physical barriers
o Skin: provides surface protection against invasion from
parasites
o Mucous membranes: provide external barriers to parasite
entry
o Tight junctions: between epithelial cells, prevent passage
of small molecules
o Low pH of vaginal secretions and gastric juices: present
a hostile environment to microorganisms
Chemical components of body fluids
o Lipase content of breast milk (toxic to Giardia)
o Lysozyme in tears and saliva (with the IgA content): able
to destroy microorganisms
Physiologic function of the body
o Peristalsis: motion of the cilia in the digestive tract helps in
expelling parasites
o Coughing: enables expectoration of certain parasites
Immunity and immune response
o Causes parasite to develop parasite evasion mechanisms
o Parasites eventually become resistant to the immune
response
o Absolute immunity rarely happens
o Host can also recognize the invading parasite through its
pathogen-associated molecular patterns
 Can also recognize through toll-like receptors
(recognize specific molecules that are nonnative to the
body, activated by bacterial components)
PARASITE EVASION MECHANISMS
 Resistance to immune response
 Immune suppression
 Antigenic variation
o Variant surface glycoproteins (VSGs)
o Variant surface proteins (VSPs)
o Parasite changes its surface proteins or glycoproteins to
avoid detection by the immune system
o Ex: Giardia and Hemoflagellates
 Host mimicry
o Parasite can copy certain proteins/antigens in the body
o Echinococcus granulosus larva: mimics the P antigen in
the P blood group
 Intracellular sequestration
o Parasites hide inside the cell
o Ex: Plasmodium, Babesia, Leishmania
TAXONOMY
EFFECTS OF HOST TO PARASITE
 Genetic makeup of host
o Duffy Blood Group Fy(a-b-): confers resistance to
Plasmodium vivax and Plasmodium knowlesi
o Sickle Cell Anemia: confers resistance to Plasmodium
falciparum
 Nutrition and diet
o High protein diet inhibits growth of protozoans
o Low protein diet favors development and appearance of
symptoms and complications of amebiasis
Kingdom Protista
(Protozoans)
 Phylum Sarcomastigophora
o Subphylum Sarcodina: ameba
o Subphylum Mastigophora:
flagellates (atrial flagellates and
hemoflagellates)
 Phylum Ciliophora: ciliates
 Phylum Apicomplexa: Plasmodium
o Possesses apical complex used for
invasion of host
o Class Sporozoa (form spores)
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Kingdom Fungi
Kingdom
Animalia
 Suborder Haemsporina
 Suborder Eimeria:
Cryptosporidium
 Capable of causing
Coccidiosis in animals
Phylum Microsporidia
 Intracellular parasites
 Now classified as fungi in Mycology
 Spore forming
 Possesses a polar tube (used to
penetrate the host cell)
 Ex: Enterocytozoon and
Encephalitozoon
 Phylum Aschelminthes
o Class Nematoda (roundworms)
 Phylum Platyhelminthes (flat worms)
o Class Trematoda (flukes)
 Order Digenea
o Class Cestoda (tapeworms)
TREATMENT
Deworming
Cure rate
Egg Reduction
Rate
Selective
Treatment
Targeted
treatment
Universal
Treatment
 Use of anthelminthic drugs in an
individual or public health program
 Number of previously positive subjects
found to be egg negative
 Percentage fall in egg counts after
deworming
 Individual-level deworming
 Selection for treatment based on
presumptive grounds
 Used in whole populations or defined
risk groups
 Group-level deworming
 Risk group to be treated may be
defined by age, sex, etc.
 Population-level deworming
Preventive
chemotherapy
Coverage
Efficacy
Effectiveness
Drug
resistance
 Community is treated irrespective of
age, sex, infection status, etc.
 Regular, systematic, large-scale
intervention through administration of
one or more drugs to selected
population groups
 Proportion of target population reached
by the intervention
 Effect of a drug
 Measure of the effect of a drug
 Genetically transmitted loss of
susceptibility to a drug
PREVENTION AND CONTROL
Morbidity
control
Informationeducationcommunication
(IEC)
Environmental
management
Environmental
sanitation
Sanitation
 Avoidance of illness caused by
infections
 Health education strategy
 Aims to encourage people to adapt
and maintain healthy life practices
 Planning, organization, performance,
and monitoring of activities for
medication or manipulation of
environmental factors
 Done to prevent or minimize vector or
intermediate host propagation
 Also done to reduce contact between
humans and infective agent
 Intervention to reduce environmental
health risks
 Includes safe disposal and hygienic
management of human and animal
excreta, refuse, and waste water
 Provision of access to adequate
facilities for safe disposal of human
excreta
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AMEBA, FLAGELLATES, & CILIATES
PROTOZOANS
 Eukaryotic organisms (possesses nucleus and organelles)
 Varies in shape, size locomotion
 Reproduce asexually (binary fission) or asexually and
sexually (in Plasmodium species)
 Do not possess cell walls (only found in bacteria, plants, and
fungi)
 Consist of nucleus and cytoplasm
o Nucleus: genetic material
 Contains nucleolus or karyosome (RNA material) or
endosome
o Cytoplasm: consists of 2 regions
 Endoplasm: for metabolism and nutrition
 Ectoplasm: hyaline (clear) structure for protection
SARCODINA
 Possess peripheral chromatin
 Nucleus is vesicular (looks like it has holes or spaces inside)
 All are commensal except E. histolytica
STAGES OF DEVELOPMENT
 Trophozoite: motile or vegetative stage
o Seen in watery, loose, or mucus-filled stool
o Labile: breaks easily (especially in the absence of water)
o stains are added to visualize the nucleus
 buffered Methylene Blue (either Nair’s or Quensel’s)
 Cyst: nonmotile stage
o Circular/round
o Resistant
o Infective stage for most ameba
o Immature cyst: pre-cyst
o Mature cyst: metacyst
o Seen in formed stool (as stool is more formed, there are less
trophozoites)
o Stained with Lugol’s Iodine (I2) and D’Antoni’s Iodine
 Cannot be used for the trophozoite because iodine is toxic
 Ameba
 Possesses pseudopodia used for locomotion
 Inhabits the large intestine except for E. gingivalis (inhabits
the mouth/oral cavity)
PATHOGENIC AMEBA
Ingestion of Cyst
Multiplication of
Trophozoites
Trophozoites and
Cysts go to the
stool
Life Cycle
 Cyst goes to stomach
 Excystation takes place
 pH should be alkaline or neutral (acidic
pH does not favor formation of
trophozoites)
 takes place in large intestine
 multiplication through binary fission
 usually produces 4 trophozoites from 1
cyst (but not for all organisms!)
 whether trophozoites or cysts appear
depends on the type of stool (if formed
or watery)
Entamoeba histolytica
MOT: ingestion of infective cyst
Habitat: large intestine
Only pathogenic amoeba
Subphylum Sarcodina, superclass Rhizopoda, class Lobosea, order Amoebida, family Entamoebidae
Cyst is resistant to gastric acidity and desiccation, can survive in a moist environment for several weeks
Trophozoites multiply by binary fission
Entamoeba species: spherical nucleus, distinct nuclear membrane lined with chromatin granules, small karyosome near center of
nucleus
Trophozoite
Cyst
Nucleus
1 nucleus (vesicular appearance)
4 nuclei (ideally)
Karyosome
Centrally located karyosome
Small, centrally located karyosome
Peripheral chromatin
Fine, evenly distributed
Fine, evenly distributed
Appearance
Clean-looking cytoplasm
Thin wall, hyaline appearance, highly refractile
Additional structures
Chromatoidal bar
 Finger-like appearance of pseudopodia
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 Hematophagus: presence of ingested RBCs
(because the organism is invasive)
Motility
Epidemiology
Virulence Factors
Laboratory Diagnosis
Treatment and
prevention
 Food reserve, energy stores
 Chemical composition: crystalline RNA
 Shape: sausage or cigar shaped
*also has a glycogen vacuole
Nonmotile
Unidirectional, progressive (moves from one point
to another)
 Worldwide distribution
 More prevalent in tropics
 High risk groups: sexually active, MSMs, food handlers
 Non-pathogenic E. histolytica look-alikes
o E. dispar
o E. moshkovskii (also called Laredo strain)
o E. Bangladeshi (all human isolates of this belongs to group ribodeme 2
o All morphologically the same with E. histolytica, but grows in room temp (E. histolytica grows at 37
degrees Celsius)
o Can be differentiated through molecular techniques, isoenzyme analysis, zymodeme analysis, and
checking the trophozoites for ingested RBCs
 Molecules produced that add to their effectiveness and enable them to replicate and disseminate within a
host
 Lectin (GaI, GaINAc Lectin) – for attachment
 Amebapores – holes on lining of large intestine
 Cysteine Proteinases – for tissue disruption and spread of infection (allows parasite to penetrate
mucosa and adhere to underlying layer surrounding the tissues)
 Ova and Parasite Examination of Stool
o Minimum of three stool specimens collected on
different days
o Direct Fecal Smear
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Less sensitive because of the lower
amount of stool (2 mg)
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Might give a negative result
o Concentration Techniques
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FECT (Formalin ether concentration
technique)
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Increase sensitivity of test, cyst can be recovered
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Merthiolate Iodine Formalin Concentration Test (MIFC)
o Permanent Stained Smear
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Iron Hematoxylin (classic method)
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Trichrome Stain (what is used nowadays)
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Confirm presence of protozoan
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More detailed (you can see the chromatoidal bar)
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Saline and methylene blue: Entamoeba species will stain blue (differentiates them from
WBCs)
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Saline and iodine: nucleus and karyosome observed (to differentiate from nonpathogenic
amebae)
o Charcot-Leyden crystals can be seen in the stool
 Culture
o Boeck’s, Rice Egg Saline, Diamond, Balamuth’s Egg Yolk Infusion
 Serology (detection of antibodies)
o ELISA (Enzyme-linked immunosorbent assay): uses antibodies and color change to identify a
substance
o IHA (Indirect hemagglutination): method for quantifying relative concentration of viruses, bacteria, or
antibodies
o Differentiation between E. histolytica and E. dispar
o Counter immunoelectrophoresis (CIE), agar gel diffusion (AGD), indirect fluorescent antibody test
(IFAT)
 Molecular methods
 Rectal biopsy (ulcer, H&E stain used)
 Examination of Liver Aspirates
 Ultrasound, CT scan, MRI for early detection of ALA
 Metronidazole: drug of choice for symptomatic cases
 Other 5-nitroimidazole derivatives: tinidazole and secnidazole
 Diloxanide Furoate: for asymptomatic cases
 Iodoquinol: alternative drug
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COMMENSAL AMEBAE
Entamoeba coli
 Transmitted via ingestion of infective cyst
 More common than other human amebae
Trophozoite
1 nucleus
Eccentric
Coarse, rough
Dirty-looking
cytoplasm (contains
bacteria, debris,
yeast)
Cyst
8 nuclei
Eccentric
Coarse, rough
Larger than E. histolytica,
thick cystic wall
Additional structures
Blunt, wider appearance of pseudopodia
Motility
Multi-/non-directional, non-progressive
Chromatoidal bar
 Broom stick/witch broom/ splinter
Nonmotile
Nucleus
Karyosome
Peripheral chromatin
Appearance
Entamoeba hartmanni
 Small race of E. histolytica
Nucleus
Karyosome
Peripheral chromatin
Additional structures
Motility
Trophozoite
1 nucleus
Centrally located
Fine, evenly distributed
Pseudopod
(similar to E.
histolytica)
Cyst
1-2 nuclei only (mature cyst can have 1-4 nuclei)
Centrally located
Fine, evenly distributed
Diffuse glycogen
vacuole/mass (not
seen in permanent
stain)
Sluggish movement, non-progressive
Nonmotile
Entamoeba polecki
Ameba of pigs and monkeys
Most common parasite in Papua New Guinea
May resemble other Entamoeba species
Zoonotic infection: can be passed from animals to humans
Trophozoite
Nucleus
1 nucleus
Karyosome
Centrally located
Appearance
Almost the same appearance as E. histolytica
Additional structures
Similar to E.
histolytica
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Cyst
1 nucleus
Large, centrally located
Almost the same appearance as E. histolytica
Chromatoidal bar
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Angular/pointed
appearance
Motility
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Unidirectional, progressive, sluggish
Nonmotile
Entamoeba chattoni
Seen in apes and monkeys
Use molecular techniques and isoenzyme analysis to differentiate from E. polecki
Morphologically similar to E. polecki
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Endolimax nana
Smallest intestinal amebae (as small as RBC, 6-8 um)
Commensal
Endolimax: vesicular nucleus with a relatively large, irregularly shaped karyosome
Trophozoite
Cyst
Nucleus
1 nucleus
4 nuclei
Karyosome
Large, irregular
Large, prominent, blot-like
Peripheral chromatin
None
None (this is only found in Entamoebas!)
Appearance
Ingested bacteria,
Oval, cross-eyed
blunt and hyaline
pseudopodia, food
vacuoles are also
present (which
may contain
bacteria)
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Motility
Unidirectional, non-progressive, sluggish
movement
Nonmotile
Iodamoeba butschlii
ameba of swine (pigs)
large, chromatin-rich karyosome surrounded by a layer of achromatic globules and anchored to the nuclear membrane by
achromatic fibrils
Trophozoite
Cyst
Nucleus
1 nucleus
1 nucleus
Karyosome
Large, eccentric
Large, eccentric
Peripheral chromatin
None
None
Appearance
“Basket of
Oval, also has
Flowers”
basket of flowers
appearance
appearance
(due to
achromatic
granules),
triangular
shaped
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Additional structures
Motility
Glycogen vacuole (Iodine used to visualize this)
Sluggish, non-progressive
Glycogen vacuole (Iodine used to visualize this)
Nonmotile
Entamoeba gingivalis
NO CYST STAGE
Ameba of oral cavity (gum line)
Also found in tartar, gingival pockets of teeth, and tonsillar crypts (of unhealthy mouths, but may
also be in healthy mouths)

May also be seen in the genital tract

Scavengers, eat debris

Can also ingest RBCs (but it’s rare)

Transmitted via direct-contact (kissing, sharing of personal items)

First amoeba in man

Can be seen in sputum sample (can go to the lungs)

Also found in AIDS patients

Found even in healthy people

Non-pathogenic, but can be seen in patients with pyorrhea alveolaris (gum infections)
Trophozoite
Nucleus
1 nucleus
Peripheral chromatin
Fine, evenly distributed
Additional structures
 Capable of ingesting WBCs
 Numerous, blunt pseudopodia
 Numerous food vacuoles that contain cellular debris (mostly leukocytes from the ingested WBCs)
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10
N. Villanueva
DISEASES OF AMEBAE FOUND IN HUMANS
Disease manifestation
Asymptomatic Carrier State
(90% of cases)
Intestinal Disease (10% of
cases)
Entamoeba histolytica
Signs and Symptoms
Excrete cysts
 Incubation period: 1-4 weeks
 Bloody diarrhea, dysentery (majority of cases), abdominal pain, flatulence, weight loss,
chronic fatigue
 Release of enzymes to lyse mucosal lining
 Formation of flask-shaped ulcers by the trophozoites
 Excess mucus in stool
 Tenesmus: cramping rectal pain
 10 bowel movements per day
 Clinical Forms:
o Fulminating Colitis (inflammation of colon)
 Can lead to perforation and secondary bacterial peritonitis (most serious complications)
o Amebic Appendicitis
o Ameboma (granulomas, chronic inflammations, can be mistaken as carcinomas or cancer)
Extra-intestinal Disease (usually  Ectopic form of amebiasis
affects the upper lobe of the
 Amebic Liver Abscess (ALA): liver aspirate (like anchovy sauce) where you can find
liver because blood vessels are
trophozoites
connected to the small
o Can lead to rupture into the pericardium, rupture into the pleura, super infection, and
intestine)
intraperitoneal rupture
 Cardinal signs: fever and right upper quadrant pain
 Tender liver (tender: painful when you touch or palpate)
 Hepatomegaly (abnormal enlargement of liver)
 Cutaneous Amebiasis (amebiasis cutis): rare, infection of skin and soft tissue
 Skin rupture
 Affects inguinal areas
 Can be transmitted sexually
 *amebiasis is characterized by low amount of WBCs in stool
 Can cause lung abscess (found in sputum) and brain abscess
 Secondary amebic meningoencephalitis (occurs in 1-2%)
 Renal involvement is rare
 Genital involvement
o Caused by fistulae from ALA and colitis or primary infection through sexual transmission
Amebiasis IS DIFFERENT from bacterial dysentery
 In amebiasis, there is mucus and blood in the stool
 There is no granulocytosis and no high fever
 There is also a fishy smell of the stool
Laboratory Diagnosis for Commensal Amebae
 Stool examination
 FECT and iodine stain useful to differentiate the species
 E. gingivalis: swab between gums and teeth (examined for trophozoites)
 DFS
 Concentration techniques (FECT and zinc sulfate flotation) useful for recovering cysts
*no treatment necessary for commensal amebae (they do not cause disease)
11
N. Villanueva
FREE-LIVING PATHOGENIC AMEBAE
 Found inhabiting lakes, pools, tap water, air conditioning units, and heating units
 Parasites are facultative (with a free-living and parasitic phase)
Person swims in
contaminated
water
Trophozoite goes
straight to the brain

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Life Cycle
Parasite enters via olfactory region
Parasite can also enter through the skin
Parasite cannot survive in salt water
Infective stage: trophozoite
Targets the CNS
Brain tissue or CSF can be examined
Naegleria fowleri
Belongs to family Vahlkampfiidae
Free-living ameboflagellate (has an ameba and flagellate form)
Only Naegleria species that can infect humans
Thermophilic: thrive best in hot springs and other warm aquatic environments
Trophozoites replicate by promitosis
Cyst found only in the environment
Enters the body through the olfactory epithelium, respiratory tract, and the skin and sinuses
Targets the brain tissue (trophozoite goes straight to the brain)
Cyst: spherical and single-walled
Trophozoite: 1 nucleus, large and dense karyosome, cytoplasm is granular and contains many vacuoles
o Ameboid form: Limax-form (slug-like)
o Ameboflagellate: 2 anterior flagella

Trophozoites also characterized by blunt, lobose pseudopodia and directional motility
Disease Manifestation
 Primary Amebic Meningoencephalitis (PAM)
and Pathology
o Inflammation of meninges in the brain
o Can affect healthy people, fast progression
o Very fatal
o When you swim in contaminated pools, lakes, and rivers
o Signs and symptoms: headache, fever, nausea, vomiting, nuchal rigidity, rhinitis, lethargy, olfactory
problems, mental status changes, mental confusion, coma
o Incubation period: 2-3 days or 1-2 weeks
o Patients usually dead after 1 week
o Brain has hemorrhaging (has lots of WBCs, especially neutrophils)
o Usually diagnosed post-mortem
o Few cases in the PH, usually in US
 Pathogenic determinant (virulence factor)
o Presence of amebostomes (food cups)
o Used to attach to the brain
o Releases enzymes (phospholipases) to destroy brain tissue
o Other pathogenic determinants include (produces a cytopathic effect on host tissues):

Secretion of lytic enzymes

Membrane pore-forming proteins

Induction of apoptosis

Direct feeding of the ameba
Laboratory Diagnosis
 Wet mount examination of CSF (look for trophozoite)
 Smears stained with Wright’s or Giemsa
 Biopsy of tissue
 CSF Analysis
o Nonspecific for N. fowleri
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12
N. Villanueva
Treatment and
prevention






Parasite enters through
the nose
Parasite enters through
the eyes
Parasite enters through
ulcerations in the skin
Reproduce in the body
o Decreased CSF glucose
o Increased protein
o High WBC (neutrophilic predominance)
Culture (Bacteria Seeded Agar Culture), Modified Nelson’s Medium
Molecular methods
Amphotericin B with Clotrimazole
New agents: Azithromycin, Voriconazole
Most die before effective treatment
o Symptoms of PAM indistinguishable from bacterial meningitis
o Patients usually treated with antibiotics, which have no effect on Naegleria
Avoid diving and swimming into warm and stagnant freshwater pools, water discharge, and
unchlorinated pools
Life Cycle
Goes to brain and affects CNS
Causes blindness
Causes lesions on the skin (especially in AIDS
patients)
Through mitosis
Acanthamoeba spp.
Family Acanthamoebidae
Acanthamoeba castellani (most common); A. culbertsoni; A. hutchetti; A. polyphaga; A. rhysoides
Free-living ameba
Aquatic organism
Found in a myriad of natural and artificial environments
Can survive even in contact lens solutions
Entry can occur through the eyes, nasal passages to the lower respiratory tract, or ulcerated or broken skin
Possible reservoir hosts for medically important bacteria such as Legionella spp., mycobacteria and gram-negative bacilli such
as E. coli

Both trophozoite and cyst are its infective stages

Trophozoites reproduce by binary fission

Trophozoites
o Eats gram negative bacteria, blue-green algae, or yeasts
o Can adapt to feed on corneal epithelial cells and neurologic tissue

through phagocytosis and secretion of lytic enzymes

Trophozoite transforms to cyst when environmental conditions are unfavorable
Trophozoite
Cyst
Nucleus
Single large nucleus
Single large nucleus
Karyosome
Centrally located, densely staining
Large karyosome
Additional structures

characteristic “thorn-like” appendages (acanthapodia)
 Double-walled cyst
o “Acantha”- spring
o Outer wall: wrinkled
o “Spring projections of the pseudopod”
o Inner wall: polygonal
o For locomotion
o Evident on phase-contrast microscope

Contractile vacuoles

Large endosome

Finely granulated
cytoplasm

Eats gram negative
bacteria

Can eat the host’s
tissues
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13
N. Villanueva
Disease Manifestation
and Pathogenesis



Laboratory Diagnosis



Treatment

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
Prevention
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
Acanthamoeba Keratitis
o Parasite enters through eyes
o Acanthamoeba was first described in 1974 as an opportunistic ocular surface pathogen
o Associated with use of improperly disinfected soft contact lenses
o Symptoms: severe ocular pain, blurring vision, corneal ulceration with progressive corneal
infiltration
o Primary amebic infection or secondary bacterial infection may lead to hypopyon formation
o May lead to scleritis and iritis, and vision loss
o Can be mistaken for herpes keratitis (to differentiate, herpes has no ocular pain)
Granulomatous Amebic Encephalitis (GAE)
o Stamm in 1972- documented Acanthamoeba as causative agent of human GAE using indirect
fluorescence microscopy
o Disseminated disease in lungs and brain
o Usually occurs in immunocompromised hosts (chronically ill and debilitated patients, those on
immunosuppressive agents like chemotherapy and antirejection medications)
o AIDS patients have the highest risk of acquiring this
o Incubation period: 10 days
o Chronic, slow in progression (long-standing)
o Signs and symptoms: destruction of brain tissue, meningeal irritation, fever, malaise, anorexia,
increased sleeping time, severe headache, mental status changes, epilepsy, and coma
o Incubation period: approximately 10 days
o Normally results in coma or death (has poor prognosis)
Cutaneous Lesions
o Presence of hard erythematous nodules or skin lesions
o Common in AIDS patients
o Parasite enters through skin
Granulomatous Amebic Encephalitis (GAE)
o Usually diagnosed after death/ post-mortem
o AIDS patients have the highest risk of acquiring this
o Not as common as other infections of the CNS like Cryptococcus meningitis and toxoplasmosis
o Can rarely be demonstrated in Cerebrospinal fluid
Acanthamoeba Keratitis
o Epithelial biopsy or corneal scrapings (stained with Calcofluor White, then viewed under the
fluorescence microscope)
o Caused by A. castellani; A. culbertsoni; A. hutchetti; A. polyphaga or A. rhysoides
Culture: Cubertson’s Medium; Non-nutrient medium with Gram negative bacteria (usually
Escherichia coli)
Molecular methods
Very fatal once cerebral manifestations appear
Fluorocystine, Ketoconazole, Amphotercin B
Acanthamoeba Keratitis
o Early recognition with anti-amebic agents can preclude the need for extensive surgery
o Clortrimazole combined with pentamidine, isethionate, and neosporin (accdg. To D’ Aversa)
o Polyhexamethylene biguanide, propamidine, dibromopropamidine isethionate, neomycin,
paramomycin, polymyxin B., ketoconazole, miconazole and itraconazole
o Avoid tropical corticosteroids (retard the immune response)
o Advanced forms require debridement
o Deep lamellar keratectomy (procedure of choice)
Granulomatous Amebic Encephalitis (GAE)
o Combination of amphotericin B, pentamidine isethionate, sulfadiazine, flucytosine, fluconazole or
itraconazole
o Decompressive frontal lobectomy and treatment with amphotericin, cotrimoxazole, and rifampin
(could work too)
Exposure is unavoidable
Sanitation (best way)
Infection can be prevented by a robust immune system, except in immunocompromised areas like
cornea
Avoid rinsing of contact lens in tap water
Prolonged heating and boiling kill amebic trophozoites and cyst forms
Find disinfectants that are more resistant than chlorine
14
N. Villanueva
Balamuthia mandrillaris

Family Leptomyxidae

New species causing amebic meningoencephalitis

Also causes Granulomatous Amebic Encephalitis (GAE)

Cysts have a characteristic wavy appearance

Trophozoites are branching

Almost the same appearance with Acanthamoeba

Both cysts and trophozoites can be seen in the brain (when infected)
Other free-living ameba that causes amebic encephalitis

Sappinia diploidea

Hartmanella vermiformis – considered now as opportunistic
INTESTINAL FLAGELLATES





All inhabit the large intestine, except Giardia lamblia (small intestine), Trichomonas vaginalis (urogenital), Trichomonas tenax (mouth)
All undergo encystation, except Trichomonas species and Dientamoeba fragilis
All are commensals except Giardia lamblia, Dientamoeba fragilis, Trichomonas vaginalis
Flagella is attached to the blepharoplast found on the body of the parasite
All undergo asexual reproduction through binary fission
Ingestion of cyst
Reproduction
takes place in the
small intestine
Parasite passed in
the stool
Life Cycle
 Released in the small intestine
 Excystation takes place
Reproduce through binary fission
(longitudinal)
 Either cyst or trophozoite
 Depends on type of stool
Giardia lamblia
Also known as G. duodenalis and G. intestinalis
Mode of transmission: ingestion of infective cysts (from fecally contaminated water or food)
Zoonotic
Habitat: small intestine (duodenum, jejunum, and upper ileum), only one in the small intestine, the rest of the intestinal
flagellates are located in the large intestine

Low infective dose (only need to ingest around 8-10 cysts to be infected, reason for outbreaks of diarrhea)

Beavers: reservoir hosts

Reproduce by binary fission, longitudinal

Prefers alkaline pH (7.8-8.2), the more alkaline, the more it attaches
Trophozoite
Cyst
Nuclei
2 nuclei (ovoidal)
4 nuclei
Appearance
Pear/pyriform shape, old man’s face with
Refractile/clear cyst wall (hyaline), oval shaped
eyeglasses
Additional structures
 Axostyle
 Median/parabasal bodies (2)
 For support
 Energy structures
 1 pair anterior flagella
 Axoneme (multiple axostyles)
 2 pairs lateral flagella
 Deeply stained curved fibrils
 1 pair conal/posterior flagella
 2 Ventral sucking discs (virulence factor)
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15
N. Villanueva
*also has median/parabasal bodies (it has a
clawhammer shape)
Motility
Disease
Pathology
Epidemiology
Laboratory Diagnosis

“Falling Leaf Motility”
Nonmotile
 Giardiasis
 Traveller’s Diarrhea (can also be caused by E. coli)
 Backpacker’s Diarrhea
 Beaver Fever
 Gay Bowel syndrome
 Incubation period: 1-4 weeks (average 9 days)
 Explosive Watery Diarrhea
 Abdominal pain

Excessive flatulence
 If not treated promptly, will result in Chronic Diarrhea
o Recurrence of loose (greasy, frothy) foul-smelling stools (odor of rotten eggs due to hydrogen
sulfide)
o Steatorrhea: abnormal quantities of fat in the stool
o Electrolyte loss
o Weight loss
o Malaise
o Low grade fever
 Alteration of mucosal lining
o Ventral sucker (virulence factor)
o Lectin (type of sugar that helps attach to small intestine)
 Leads to Villous Flattening and Crypt Hypertrophy
o Malabsorption and maldigestion
 Presence of VSPs
 Can rearrange cytoskeleton in human colonic and duodenal monolayers
 Has the ability to disrupt cellular tight junctions and increase epithelial permeability
 Worldwide
 Common in children (day care centers), crowded places, mental institutions, travelers, and the people
who clean the septic tank
 Increasing cases among MSMs (Gay Bowel Syndrome)
 Sewage and irrigation workers at risk
 Prevalent among humans: assemblage A&B
 Blood Type A: higher risk
 Usual specimens: stool/feces
 Collect 3 specimens in the span of 10 days
 DFS (to find trophozoites and cyst)
 Concentration techniques (FECT)
 Stained smears (permanent)
 Entero-test
o Usually done if you are negative in DFS
o Beale’s String Test
o Swallow a capsule (has string and yarn inside)
o Loose end placed on face
o Yarn will go to the duodenum (where the parasites are)
o After 4 hours, pull the string
o Prepare smear from the string and look for the parasite
o String should be green
 Duodenal aspirates
16
N. Villanueva
 Serology
 Molecular methods
 Biopsy
o Tissue from intestine
o Check for flattening of villi
Treatment and
Prevention

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
Ingestion of
trophozoites

Reproduction takes
place


Replicates by binary fission
Trophozoites will be located in the lumen of
the colon
Parasite passed in the
stool


Only trophozoite
Transmission can occur via helminth eggs
(Ascaris and Enterobius)
Drug of choice: metronidazole
Alternative drugs: tinidazole, furazolidone, albendazole
Wash hands
Proper sanitation and hygiene
Proper and sanitary disposal of human excreta (to prevent contamination of food and water supply)
Chlorine cannot kill cysts
o Use iodine to disinfect water
Life Cycle
Goes to the large intestine
Dientamoeba fragilis

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Formerly classified as an ameba
Now an ameboflagellate
No cyst stage, infective stage is the trophozoite
Habitat: colon/large intestine
Mode of transmission: oral fecal (ingestion of trophozoites)
Relative of Trichomonas
Usually ingested with Enterobius and Ascaris
 acts as carriers of D. fragilis
reproduction through binary fission
high prevalence in developed countries with high sanitation standards (Israel, Holland, Germany, etc.)
Trophozoite
Nucleus
Karyosome
Appearance
2 nuclei (hence Dientamoeba)
Rosette/rose-like

sometimes not detected/seen
 fragilis – fragile
 its easily destroyed
Additional structures




May have ingested bacteria
NO VISIBLE FLAGELLA
 Only called a flagellate because its structures are similar to
what flagellates have
Pseudopodia (angular appearance)
Pseudopodia produces non-progressive movement
17
N. Villanueva
Symptoms of infection
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Gastroenteritis
Diarrhea
Abdominal pain
Anorexia (loss of appetite)
Nausea
Vomiting
Fatigue
Weight loss
Laboratory Diagnosis



Multiple fixed and stained fresh stool samples
Purged stool specimens
Prompt fixation with polyvinyl alcohol or Schaudinn’s fixative
Treatment


Iodoquinol
Other drugs: tetracycline and metronidazole
Ingestion of cysts
Parasite is passed
in the feces
Life Cycle
Parasite goes to the colon/large intestine
and develops and reproduces
Cysts usually contaminates food, water,
hands of people, and other fomites
Chilomastix mesnili
 Commensal parasite of the colon/large intestine (cecal region)
 Infective stage: cyst (ingestion)
 Excystation happens in the small intestine
 Trophozoites then go to the large intestine
 Worldwide distribution
 No treatment indicated
 Prevention and control measures: improved sanitation and personal hygiene
Nucleus
Appearance
Additional structures
Trophozoite
1 nucleus, with prominent karyosome
Pyriform, pear-shaped, curved posture, twisted jaw
appearance



3 anterior flagella
1 flagella near cytostome (mouth of the
parasite)
Cytostomal fibril (shepherd’s crook
appearance)
Cyst
1 nucleus
 American lemon appearance
 Nipple-shaped cyst
 7-10 um in size
 Hyaline knob (protruding structure)
18
N. Villanueva

Motility
 Cytostomal fibril (shepherd’s crook)
Spiral groove
Boring/Rotary/Corkscrew, Spiral forward
Nonmotile
Enteromonas hominis



Commensal
Almost the same life cycle as Chilomastix
Mode of transmission: ingestion of cysts
o Contamination of water, food, or hands/fomites with infective cysts
Trophozoite
Nucleus
Appearance
1 nucleus
Oval-shaped


Motility
Cyst
2 or 4 nuclei (located at ends of the cyst)
Oval-shaped
3 anterior
flagella
1 posterior
flagella
Jerky motility
Nonmotile
Retortamonas intestinalis



Commensal
Mode of transmission: ingestion of cysts
Same life cycle as E. hominis
o Contamination of water, food, or hands/fomites with infective cysts
Nucleus
Appearance
Trophozoite
1 nucleus

1 anterior and 1 posterior
flagella

Motility
Cytostome: cleft-like
Jerky motility
Cyst
1 nucleus

Pear-shaped or slightly
lemon-shaped

Cytostomal fibril
o Bird’s beak
appearance
Nonmotile
19
N. Villanueva
UROGENITAL FLAGELLATES
Trichomonas vaginalis
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Pathogenic and largest (among the three species)
Causes Trichomoniasis (STD, affects both males and females)
Habitat: Urogenital Area (females: vagina, males: urethra and prostate)
Mode of transmission: intimate contact, infant delivery (during delivery only, not vertical transmission and not transmitted via
the placenta), contaminated towels and underwear
No cyst stage
Reproduces by longitudinal binary fission
Most prevalent nonviral sexually transmitted infection
Nucleus
Appearance
Additional structures
Motility
Disease Manifestation
Trophozoite
1 nucleus
Pyriform, Pear-shaped

4 anterior flagella

1 flagella embedded in the undulating membrane

Axostyle

Cytostome

Undulating membrane
o Found on the lateral portion
o Wave-like structure
o For motility
o Length is crucial for identification
o ½ of body length
o Attached to body of parasite via costa

Rib-like structure

Distinct for this parasite

Siderophil granules
o Also known as paraxostylar granules
o Iron-rich
o Near axostyle
o No distinct function (only for identification)

Vacuole with bacteria
Jerky tumbling motility

Incubation period: 4-28 days

Proliferating colonies cause degeneration and desquamation of vaginal epithelium (followed by
leukocytic inflammation of the tissue layer)

Females: mostly symptomatic (70%)
o Vaginal pruritus (vaginal itching), with a burning sensation
o Mucopurulent discharge: frothy, yellow, or green

Mucopurulent discharge is the emission or secretion of fluid containing mucus
and pus (muco- pertaining to mucus and purulent pertaining to pus) from the
eye, nose, cervix, vagina or other part of the body due to infection and
inflammation
o Dysuria (painful urination)
o Lower abdominal pain
o Atypical pelvic inflammatory disease

Can lead to sterility
o Strawberry cervix: inflamed cervix

Red dots can be seen (hemorrhages)
o Secondary bacterial infection of the urogenital tract
o When acute condition changes to the chronic stage, secretion loses purulent
appearance due to decreases in trichomonads and leukocytes, increase in epithelial
cells, and establishment of a mixed bacterial flora
o Trichomonads associated with postpartum endometritis

Males: mostly asymptomatic
o Few symptomatic males show non-gonococcal urethritis, epididymitis, prostatitis
o When not treated: can lead to sterility

Infants: can get neonatal pneumonia
20
N. Villanueva
o
Pathology
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Epidemiology

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
Laboratory Diagnosis

Uses adhesins to bind to vaginal epithelial cells
o Attachment to body surface
o Adhesins have enzymes that promote tissue disruption
Immune evasion
o Presence of VSPs
o Surface coating with host proteins
o Shedding of parasite proteins
Secretion of cysteine proteinases
Cell detaching factor – cytopathic effect
Alkaline pH (of the vagina promotes infection)
STD infection
Found worldwide
Humans: only natural host
Increased susceptibility to HIV
o Because of inflammation
o Also because they are sexually active (high-risk individuals)
Symbiotic relationship with Mycoplasma hominis
o
Bacteria that causes STDs
Prevalence higher among women of child-bearing age





Wet Mounts of vaginal and urethral discharge (can also use urine samples)
o To check motility
o Low sensitivity
Stained smears (Giemsa or Pap’s)
Culture: Diamond modified medium, Feinberg Whittington, Cysteine Peptone Liver
Maltose, Simplified Trypticase Serum Semen Culture
o Gold standard, takes 2-5 days
o Best results seen with combination of urethral swabs and urine sediment
Antigen detection
Serology
Molecular methods
PCR (detects more cases with men than women)
InPouch™ TV: allows specimen to be inoculated into a sealed pouch with culture media


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

Metronidazole
Tinidazole
Have a monogamous relationship
Abstinence
Be faithful to your partner


Treatment and
prevention
From infected moms
Pentatrichomonas hominis





Commensal
Formerly known as Trichomonas hominis
Penta: has 5 flagella
Habitat: colon
Trophozoites found in contaminated food, water, or hands/fomites
Trophozoite
Nucleus
Additional structures
1 nucleus

4 anterior flagella

1 posterior flagella

Conical cytostome
21
N. Villanueva

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Motility
Axostyle
No peripheral chromatin
Undulating membrane
o Full body length
Jerky motility
Trichomonas tenax
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
Commensal
Habitat: mouth (tartar of teeth, cavities of carious teeth, necrotic mucosal cells in gingival margins)
Mode of transmission: direct contact (kissing) or use of contaminated glass or dishes (sharing of utensils)
Generally harmless
o Though there are reports of respiratory infections and thoracic abscesses in cancer and other
immunocompromised patients or in patients with other lung diseases
o Pulmonary trichomoniasis reported among those with underlying chronic pulmonary disease
o Parasite probably unable to cause disease on its own
o Presence of bacteria most probably allows it to proliferate profusely
Smallest among the species
Resistant to changes in temperature
Will survive for several hours in drinking water
Diagnosis through swabbing tartar between teeth, gingival margin, or tonsillar crypts
Treatment: metronidazole
Trophozoite
Nucleus
Appearance
Additional structures
1 nucleus
Pyriform





Motility
Jerky motility
4 anterior flagella
1 posterior flagella
Axostyle
Cytostome
Undulating membrane
o 2/3 body length
22
N. Villanueva
CILIATES
Balantidium coli
Largest protozoan infecting man
Hosts: man (pigs usually reservoir hosts, zoonotic)
Mode of transmission: ingestion of cysts
Habitat: colon (cecum)
Risk factors: close contact with pigs (in pig feces)
Cysts found in fecally contaminated food or water
Only ciliate known to cause human disease
Trophozoite
Cyst
Nucleus
2 nuclei
2 nuclei (micronucleus and macronucleus), unlike in
amebae, encystation does not result in an increase of

Micronucleus: For sexual reproduction
nuclei
o lies in concavity of macronucleus

Macronucleus: Kidney-shaped
o for asexual reproduction and
vegetative function

Mucocysts
o Extrusive organelles
o Located beneath cell membrane
Appearance
Ellipsoid, tapered in anterior portion
Spherical/Ellipsoidal (oval)
Additional
 Cytostome (can be found by observing the

Cyst wall
structures
tapered portion, since the anterior portion is
o Double-walled
tapered)
o Refractile (shiny)
o Oral apparatus

Cilia is enclosed within the cyst wall
o Through which it acquires food

Cytopyge
(anus)
o Through
which it
excretes
waste

Contractile
vacuoles: for
osmoregulation

Food vacuoles

Cilia
Motility
Thrown-ball motility
Nonmotile
Disease

Incubation period: 4-5 days
Manifestation

Causes Balantidiasis or Balantidial Dysentery
o Bloody Diarrhea
o Flask-shaped ulcers (wider and rounded)
o Extraintestinal spread may occur

Virulence factor: hyaluronidase
o Lytic enzyme that causes ulceration

Presence of Salmonella has been shown to aggravate Balantidiasis (by invading ulcers caused by the
protozoan)

Three clinical manifestations
o Asymptomatic

Do not present diarrhea

Serve as parasite reservoir
o Acute Cases (Fulminant Balantidiasis)

Diarrhea with bloody and mucoid stools

Often associated with immunocompromised and malnourished states
o Chronic Cases

Diarrhea may alternate with constipation

Accompanied with abdominal pain, cramping, anemia, and cachexia

Can spread to extraintestinal sites
o Mesenteric nodes
o Appendix
o Liver
o Genitourinary sites
o Pleura







23
N. Villanueva
Laboratory
Diagnosis
Epidemiology
Treatment and
prevention












o Lungs
Complications include intestinal perforation and acute appendicitis
Direct examination or concentration techniques
o Sedimentation or floatation
o Feces with trophozoites and cysts
Biopsy specimens (from lesions obtained through sigmoidoscopy)
Bronchoalveolar washings (in case of pulmonary infection)
Prevalence (0.02% to 1%)
Uncommon among humans
Common in institutionalized patients (in overcrowded institutions)
Areas with poor sanitation
People at risk: those in close contact with pigs or pig feces
Warm and humid climates in tropical and subtropical countries can contribute to cyst survival
Metronidazole, Iodoquinol Tetracycline
Avoid using pig feces as fertilizer
BLASTOCYSTIS HOMINIS

Currently a commensal of the GI tract
Blastocystis hominis

Classified member of Stramenopiles

Suggested new class: Class Blastocystea

Previously classified as a yeast in Schizosaccharomyces

Also previously associated with Blastomyces

MOT: ingestion of thick walled cysts

Life cycle still not fully understood
Morphologic Forms

Classic Vacuolated Form
(Central-Body Form): most
predominant
o Large central vacuole
pushes the cytoplasm
to the periphery

Granular forms: multinucleated

Multivacuolar

Avacuolar

Ameboid form: exhibit active
extension and retraction of
pseudopodia
o Nuclear chromatin
exhibits peripheral
clumping
o Intermediate stage
between vacuolar and
precystic form

Cyst: has a thick, osmophilic, and electron dense cystic wall
Disease Manifestation

Blastocytosis

Pathology is still in question and controversial

Diarrhea, nausea, anorexia

May also be associated with irritable bowel syndrome
Epidemiology

Occurs worldwide

Zoonotic

Most common subtype infecting man is subtype 3
Lab Diagnosis

DFS

FECT

Molecular methods

Stains

Culture: Boeck and Drborhlav
Treatment

Still controversial

Usually use metronidazole
24
N. Villanueva
MALARIAL PARASITES
 Intracellular protozoans
 Phylum Apicomplexa, Class Sporozoa, Suborder
Haemosporina
 Undergoes alternating sexual (sporogony) and asexual
stages (schizogony) in its life cycle
 Vector borne (Female Anopheles minimus flavirostris)
 Intermediate host: MAN
 Habitat: Liver and RBCs of humans
 Infective stage to mosquito: gametocytes
 Infective stage to man: sporozoites
 MOT: Mosquito bite, blood transfusion, congenital
Exo-erythrocytic cycle
 Can also be called pre-erythrocytic cycle
 Mosquito bites human, injects sporozoites
 Sporozoites now in blood stream
o must reach liver within 30-40 minutes (cannot stay long
because they will be destroyed by the immune system
Stage
Description
Sporozoites
 sporozoites become merozoites
infect liver
 merozoites undergo asexual
parenchyma
reproduction (schizogony)
cells
o schizogony is synchronous, periodic,
and species-determined
Merozoites form  schizont: sac-like structure with
a schizont
merozoites inside
Bursting of
 merozoites are released
schizont
o some infect other liver cells
 some remain inside liver (causes
relapse)
o become dormant (hypnozoites)
o for P. ovale and P. vivax
 recrudescence
o for P. malariae and P. falciparum
o very low level of parasitemia
o so number of malarial parasites in
the blood are low
o this leads to assuming that the
patient is negative for malaria
o parasite is still there, but you cannot
detect it
o there is sequestration of malarial
stages in the spleen
o schizogony in the RBCs
o not a true relapse
Erythrocytic cycle
Merozoites from  start of erythrocytic schizogony
liver infect
 merozoites develop into an immature
RBCS
trophozoite form
o ring-form
o red chromatin dot and ring of
cytoplasm (scant amount) stained
bluish with Giemsa
o large chromatin mass present and a
prominent ameboid cytoplasm
(spread throughout erythrocyte)
 ring form develops into a developing
trophozoite
 developing trophozoite develops into a
mature trophozoite
 mature merozoites enclosed in another
schizont
 schizont formed when the large
chromatin mass has divided into two or
more masses of chromatin with small
amounts of cytoplasm
o clumps of pigment accumulate in
middle of mature schizont
Bursting of
 merozoites released
schizont
 infects other RBCs
Gametogony
 after many cycles, gametocytes are
produced
 factors that trigger this are not
completely understood
 macrogametocyte: female
 microgametocyte: male
 gametocyte characterized by a large
chromatin mass with a blue cytoplasm
with pigment
Transmission of  uninfected mosquito will bite the
gametocytes
human
 will get the gametocytes
Sporogonic cycle
 entire cycle in mosquito: 8-35 days (depends on ambient
temperature)
Gut/GI Tract of
 mosquitoes have a different body
mosquito
temperature (colder)
 gametocytes become gametes
o microgamete and macrogamete
Exflagellation
 microgamete exflagellates
 release of 8 sperm-like structures
 fertilize female macrogamete
Fusion of
 sexual reproduction (sporogony)
gametes
 formation of zygote
Formation of
 zygote becomes elongated and motile
ookinete
o forms ookinete
 ookinete penetrates gut wall of
mosquito
 ookinete develops into an oocyst
o sac-like structures with sporozoites
Oocyst bursts
 releases sporozoites
 sporozoites migrate to salivary glands
 migrate to proboscis (mosquito is now
ready for infection)
25
N. Villanueva
PLASMODIUM SPECIES

Hematin: pigment found in Plasmodium species as a result of the parasite feeding on hemoglobin
Plasmodium falciparum
 Most prevalent Plasmodium in the Philippines
 Merozoites develop in the parasitophorous vacuolar membrane (PVM)
o Inside RBC
o Modify structural and antigenic properties of RBC
 Once merozoites invade RBCs, RBCs reduce their deformability
o Due to changes in red blood cell cytoskeleton and increase in membrane stiffness and cytoplasmic viscosity
Type of Malaria
Malignant Tertian Malaria
*or Subtertian Malaria or Estivoautumnal Malaria
Paroxysmal Cycle
36-48 hours
Type of RBC infected
All forms (high rate of infectivity)
Size of Parasitized RBC
Normal
Presence of RBC stages
Ring forms, gametocytes (developing trophozoite is rare)
Ring Forms

Delicate small ring

May have 2 chromatin dots (indicating
multiple infection)

Common multiple rings in an RBC
o Headphone/smiley
o Accole/applique: chromatin in
periphery
o Exclamation point
o Question mark
Developing Trophozoite
Schizont
Microgametocyte
Macrogametocyte
Stipplings
Complications
Heavy ring forms (commonly not seen)
8-36 merozoites

Rarely seen

Schizogony happens in the blood vessels of the internal organs

If schizont is seen, indicates poor prognosis (so much merozoites produced that they are
already seen in the peripheral blood)
 Sausage shaped
 Diffuse chromatin
 Crescent shaped
 Compact chromatin
 Laveran Bib: remnant of RBC
Maurer’s Clefts

Comma or wedge

Comma-like red dots
Malignant tertian malaria

Malaria – “bad air” (thought it came from the air)

Most virulent

Incubation period (time between sporozoite injection and appearance of clinical symptoms):
8-11 days (shortest)

Anemia is more pronounced (targets all types of RBCs)

CNS involvement is very common
o Cerebral malaria
o Because schizogony happens in the internal organs
o Affects blood vessels that supply the brain

Schizogony occurs in the internal organs
o Sequestration of RBC stages
o Hidden (because it happens in the internal organs)
o Destruction of blood vessels in internal organs
26
N. Villanueva
















Hemozoin: brown pigment in blood smears and vessels
o Metabolic product of parasite
o Other references call it the malarial pigment
Cerebral malaria – most severe form
o Unarousable coma
o Convulsions
o Cerebral ataxia
o Happens if malaria is complicated and not treated immediately
o Generally manifests with diffuse symmetric encephalopathy
Anemia
Severe blackwater fever
o Massive intravascular hemolysis and hemoglobinuria
o Hemoglobinuria: hemoglobin in the urine

Increase in RBC destruction leads to release of hemoglobin in the urinary
system

Oxidize and become black
o Most severe with interaction with anti-malarial drugs (particularly quinine)
Dysenteric Malaria
o Causes abdominal pain, hepatomegaly, upper GI bleeding, nausea (with or without
jaundice)
Algid Malaria
o Rapid development of hypotension (decrease in blood pressure)
o Impairment of vascular perfusion
Disseminated intravascular coagulation (DIC)
o Blood clots form throughout the body (blocking the small blood vessels)
Acute renal failure
o Because of hemoglobin to the kidneys
Pulmonary Edema
Tropical Splenomegaly Syndrome
o Enlargement of spleen because of recirculation of destroyed RBCs
Hypoglycemia can also happen
o Parasite ingests glucose of RBCs
o Happens when condition is severe
Shortest pre-patent period: 9-10 days (period between infection and positive lab results,
interval from sporozoite injection to detection of parasites in the blood)
pre-erythrocytic stage: 5 ½ - 7 days
nephrotic syndrome is rare
relapse does not occur
Recrudescence: renewal of parasitemia from persistent undetectable asexual
parasitemia
o Signs and symptoms arising from undetected asexual parasitemia
t
Plasmodium vivax
 Most prevalent species (widest distribution)
 Infections usually benign (targets only young RBCs, with ovale)
o Relapses can occur (but this is a case-to-case basis)

Renewed asexual parasitemia

Disease manifests again after many years

Do not need to get bitten again for relapse

Reactivation of hypnozoites

Factors that promote reactivation

Stress

High fever

Pregnancy

Depression

Immunocompromised patients

Exo erythrocytic schizogony
o Vivax more severe when compared to ovale
 Incubation period: 8-17 days
 Pre-patent period: 11-13 days
 Pre-erythrocytic stage: 6-8 days
 Anemia is mild to moderate
27
N. Villanueva
 Rare involvement of CNS
 Possible nephrotic syndrome
 No recrudescence
Type of Malaria
Paroxysmal Cycle
Type of RBC infected
Size of Parasitized RBC
Presence of RBC stages
Ring Forms
Developing Trophozoite
Schizont
Microgametocyte
Macrogametocyte
Stipplings
Benign Tertian Malaria

Less virulent
44-48 hours
Young RBCS (reticulocytes)
Enlarged RBCS (1.5-2 times)
All stages present

Schizogony happens in the peripheral blood

Large ring form

Big/heavy chromatin dot

Signet ring appearance
Ameboid/bizarre looking
12-24 merozoites

Round

Large pink to purple chromatin mass surrounded by a pale halo

Gametocytes difficult to see

Round

Eccentric chromatin mass
Schuffner’s dots

Eosinophilic
Plasmodium ovale
 Infections usually benign (targets young RBCs only, with vivax)
o Spontaneous recovery can occur after 6-10 paroxysms
o Relapses can also occur
 Presence of 2 distinct nonrecombining species
o Classic: Plasmodium ovale curtisi
o Variant: Plasmodium ovale wallikeri
 Infections may no longer be limited to areas of Tropical Africa, Middle
East, Papua New Guinea, and Irian Jaya (Indonesia)
 Incubation period: 10-17 days
 Pre-patent period: 11-13 days
 Pre-erythrocytic stage: 9 days
 Mild anemia
 Possible CNS involvement
 Rare nephrotic syndrome
 No recrudescence
Type of Malaria
Paroxysmal Cycle
Type of RBC infected
Size of Parasitized RBC
Presence of RBC stages
Ring Forms
Developing Trophozoite
Schizont
Microgametocyte
Macrogametocyte
Stipplings
Ovale Tertian Malaria
48 hours
Young

Enlarged RBC (more oval in appearance)

May come with a serrated or fimbriated edge
All stages present
Large rings (similar to vivax)

Non-ameboid

Ring-shaped

Similar to vivax

Serrated/fimbriated
8 merozoites
Round gametocytes (smaller than vivax)
Smaller than P. vivax
James’ dots

Schuffner’s dots in other references
28
N. Villanueva
Plasmodium malariae
Quartan Malaria
72 hours
Old RBCS (Senescent RBCS)
Normal
Few ring forms seen (mostly trophozoites and schizonts)

Heavy chromatin dot (bird’s eye appearance)

Small form
Type of Malaria
Paroxysmal Cycle
Type of RBC infected
Size of Parasitized RBC
Presence of RBC stages
Ring Forms
Developing Trophozoite
Band formation

or Inverted basket form
6-12 merozoites

rosette/fruit-pie appearance
Round gametocytes (smaller than vivax)
^same
Ziemann’s dots
Quartan Malaria

Incubation period: 27-50 days (longest)

Renal involvement
o Nephrotic syndrome is common

Proteinuria in urine

Immune complex deposition (antigen-antibody complex) in the
glomerulus/kidney

Causes activation of complement

Leads to inflammation then removal of the complex
Schizont
Microgametocyte
Macrogametocyte
Stipplings
Complications
Plasmodium knowlesi

mostly in Southeast Asia (Malaysia, Indonesia, can also be seen in Palawan)

almost the same morphology with malariae

differentiated through molecular methods (PCR) and molecular characterization

parasite of long-tailed macaques (Macaca fascicularis)
Type of Malaria
Simian Malaria, Quotidian Malaria
Paroxysmal Cycle
24 hours (has the shortest erythrocytic cycle)
Type of RBC infected
Can infect all
Size of Parasitized RBC
Normal
Ring Forms

Early ring form: like falciparum

Later ring form: like malariae
Developing Trophozoite
Band formation
VECTORS
Mosquito
Anopheles minimus
flavirostris




Description
Primary mosquito vector in the country
Only female bites (for egg nourishment and ovulation, males only go to flowers)
Night biter (10pm – 2am)
Bites indoors and outdoors
o Exophagic: likes biting outdoors
o Endophagic: likes biting indoors
29
N. Villanueva
Anopheles maculatus
Anopheles litoralis
Anopheles mangyanus
Anopheles balabacensis
Anopheles gambiae










Anthropophilic (likes biting humans) and zoophilic (also likes biting animals)
Transmits malaria in hilly or high altitudes
Mountainous areas
Zoophilic
exophagic
transmits in coastal areas
larvae breeds in salt or brackish (mix of fresh and salt water) waters
anthropophilic
transmits in forest-fringe areas (edge of the forest)
similar breeding with flavirostris

transmits in forests

breed in stagnant water, hoof prints (when water goes inside the prints), dug wells

anthropophilic

secondary vector of malaria in the country

primary mosquito vector in Africa

best vector of malaria
o bites humans only
o longer life span compared to other species
o more time to bite people
CLASSIC PAROXYSMS




Sequence of symptoms
Characteristic periodicity
Coincide with rupture of RBCs
Typical attack lasts from 8-12 hours
1. Cold stage (10-15 minutes)
a. Shivering, chilling
b. Mild shivering, then turns to violent teeth
chattering and shaking of entire body
c. Intense peripheral vasoconstriction
d. Patient may vomit
e. Young children: may have febrile convulsions
2. Hot stage or flush phase (2-6 hours)
a. High temperature, pyrexic
b. “febrile”: showing symptoms of fever
c. Fever – immune response against the parasite
d. When the parasite goes out of the cell, the body’s
temperature increases in order to destroy
microorganisms and the parasite
e. Pyrogens cause the increase in temperature (ex:
TNF: tumor necrosis factor)
f. Headache, palpitations, tachypnea, epigastric
discomfort, thirst, nausea, and vomiting
g. Temperature may reach a peak of 41 degrees
Celsius or more
h. Patient may become confused or delirious
3. Sweating stage (2-4 hours)
a. Body cannot stand high temperature for long
b. Sweating happens
c. Sweating also known as diaphoresis
d. Defervescence: abatement of fever indicated by
a decrease in body temp
4. Apyrexia
a. Normal stage, no more fever
SIGNS AND SYMPTOMS

Anemia – low RBCs and hemoglobin
o Because of increasing destruction of RBCs
Ruptured RBCs go to the spleen
Causes splenic recirculation
Leads to splenomegaly (enlarged spleen)
People with anemia have a higher chance to get
severe malaria
o But some people with anemia (sickle cell anemia)
may be immune
o Can lead to bone marrow suppression
o RBCs may also be destroyed because of formation of
immune complexes

Autoimmune destruction of RBCs

Malarial antigens on surface of RBCs attach to
antibodies

Immune complex is formed

Body destroys this
Splenomegaly, Head ache, Body pains, Nausea, Vomiting,
Pallor, Cough, Malaise, Back ache, Diarrhea, Epigastric
discomfort
Leukopenia can also be present
Prodromal symptoms (early signs or symptoms which
indicate onset of a disease)
o Feeling of weakness an exhaustion
o Desire to stretch and yawn
o Aching bones, limbs, and back
o Loss of appetite
o Nausea and vomiting
o Sense of chilling
Retinal hemorrhage
Bruxism (fixed jaw closure and teeth grinding)
Mild neck stiffness
Pouting (pout reflex may be elicited by stroking the sides
of the mouth)
Altered pulmonary function
o Air flow obstruction, impaired ventilation and gas
transfer, increased pulmonary phagocytic activity
Malaria in pregnancy
o Maternal death
o Maternal anemia
o Intrauterine growth retardation
o
o
o
o

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

30
N. Villanueva
Spontaneous abortion
Still birth
Low birth weight associated with risk for neonatal
death
Children
o Cerebral malaria, seizures, neurologic sequelae,
opisthotonos
Severe
o Impairment of consciousness and other signs of
cerebral dysfunction (delirium and generalized
convulsions)
o Severe hemolytic anemia
o hyperbilirubinemia
o
o
o


PATHOGENESIS

Primarily due to:
o RBC hemolysis
o Release of parasite metabolites
o Immunologic response
o Malarial pigment (hemozoin)

Iron porphyrin and hematin

Indicates number of parasites in the blood

Increase of hemozoin = increased number of
parasites

Increased hemozoin = more complicated
malaria




o
o
Entry of merozoite using the apical complex

3 components: rhoptries, dense granules,
micronemes
Cytoadherence

Particularly in P. falciparum

Formation of knobs on infected RBCs
 in falciparum:
 parasite forms parasitophorous vacuole in
the RBC (merozoite is inside)
o
metabolize and get glucose from the RBCs
(produces hemozoin)
infected RBC forms surface markers (knobs)
on the surface
knobs: antigens (PfEMP1)
knobs has proteins (rosettins, riffins,
histidine-rich proteins, and PfEMP1)
 histidine-rich proteins (HRP) – localize to the
cytoadherence ligands (make adhesion more
effective)
 rosettins and PfEMP1 – ligands for rosette
formation (adhere to parasitized and
nonparasitized cells + platelets)
 PfEMP1: Plasmodium falciparum erythrocyte
membrane protein – main component of the
knob
 PfEMP1 encoded by a multigene family
termed var and is clonally variant (enabling it
to evade specific immune responses)
 The knobs are adherent and sticky
 They interact with receptors on surface of
blood vessels (ICAM-1, intercellular
adhesion molecule 1)
 RBC sticks to blood vessels
 RBCs will become sequestered
 Blood vessels get obstructed
 Severe malaria happens
Soluble antigens of P. falciparum
 Induction of pro-inflammatory cytokines
 Glycosylphosphatidyl inositol (GPI) moieties
seen on surface antigens of the protozoans act
like endotoxin of gram-negative bacteria
(stimulate monocytes to release TNF or
cachexin <-implied to be cause of malarial fever)
31
N. Villanueva


Release of cytokines at time of schizont rupture:
results in paroxysms (that’s why paroxysms start
when RBCs burst)
Combination of altered RBC surface membranes
and host’s immunological response brings about
pathologic changes





o
Alteration in regional blood flow in vascular
endothelium
Altered biochemistry
Anemia
Tissue and organ hypoxia
Increased capillary permeability (allows
fluids to leak into surrounding tissues)
 Congestion in blood vessels (results in tissue
infarction and necrosis)
Alterations to the RBC surface membrane
THICK AND THIN SMEAR



EPIDEMIOLOGY











Malaria – most important parasitic infection of man
P. vivax – most prevalent species (widest distribution)
Malaria prevalent in tropical areas
o In the PH, low in visayas (may be attributed to the
many islands it has, and also to the fully implemented
vector program in the past)
Falciparum most prevalent in the PH, vivax second most
prevalent
o High endemicity: Palawan, Kalinga-Apayao, Ifugao,
and Agusan del Sur
Quartan malaria – in subtropics and temperate zones
Falciparum and ovale malaria – mostly in tropics’
Falciparum and vivax – responsible for 90% of all human
malaria cases
Mixed infections may also occur
Children: more susceptible to malaria
o Pregnant women also susceptible
Persons with African ancestry: may have innate immunity
to certain types of malaria
o Also those with Duffy blood group
o People who have problems with RBC structure (sickle
cell anemia, Glucose 6-phosphate dehydrogenase
deficiency)
o Patients with Thalassemia


Qualitative Reporting (Thick Smear)
Quantitative Reporting (Thick Smear)
#
𝑥 8000
*8000 = normal number of WBCs
*200 WBC should be present before counting, if not you have
to adjust


Sample: capillary blood, peripheral blood
Anticoagulated blood
EDTA can alter morphology of parasite
Collect sample at height of the fever (or every 6-8 hours)
Lumbar tap: shows normal to elevated opening pressure
CSF: clear, fewer than 10 leukocytes/mL, slightly elevated
protein and CSF lactic acid concentration
gold standard: microscopy
o prep of thick and thin smears
thin smear: species identification (because RBCs are
intact)
o specific but not sensitive (100-200 parasites/ul of
blood)
o has an absolute methanol fixation
o no dehemoglobinization
stain with Giemsa (pH 7.2)
o pH is adjusted using a phosphate buffer
o pH important to see structures in the RBC
alternative stain: Wright’s
# of malarial parasite/ul =
Airport malaria (u get malaria in the airport)
LABORATORY DIAGNOSIS








thick smear: quantification and screening of parasite
(because of concentrated amount of parasite in the smear)
o dehemoglobinization or “laking”: immerse thick smear
in water or put drops of water directly ->to lyse RBCs
and remove hemoglobin (helps see the parasite
more)
o no fixation
o sensitivity: 10 parasites/ul of blood
Desired number of WBCs to be counted depends on the
density of Plasmodia (or level of parasitemia)
o 200 WBCs adequate if 100 or more Plasmodia are
counted
o 500 WBCs should be counted if 99 or less Plasmodia
are counted
o 100 WBCs is enough if parasitemia is high
For Percent Infection (Thin Smears)
%infected RBCs =
.
#
𝑥 100
QUANTITATIVE BUFFY COAT (QBC)



Capillary tube with acridine orange stain
(+) bright green and yellow under fluorescence
microscope
Fill tube with blood, centrifuge, then examine buffy coat
32
N. Villanueva

Orange: stains all malarial parasites (because the
parasites have nucleic acids, and normal RBCs do not
have those)

RAPID DIAGNOSTIC TESTS (RDTs)


Immunochromatographic Mtds
Antigen detection
o HRP-II: histidine rich protein (Antigen produced by
Falciparum trophozoite and gametocytes)

Paracheck PF, ParaHIT f

Specific for Falciparum
o pLDH: parasite lactate dehydrogenase (produced
by viable parasites)

can distinguish Falciparum from non-Falciparum
species

ex: Optimal brand
o Aldolase: other panmalarial antigens

Can be positive for all malarial agents except for
knowlesi (can only distinguish it using molecular
methods)
OTHER METHODS



Serology (ELISA, IHA, IFAT)
Molecular (PCR for low parasitemia and mixed infections)
Culture: RPMI 1640









PREVENTION





TREATMENT

Chloroquine: main treatment
o DOC for uncomplicated P. falciparum, vivax,
malariae, and ovale
o Resistance has been reported
Arthemether combination treatment like arthemether
lumefantrine (coartem)
o WHO recommended drug for falciparum and malariae
o Combination therapy
Quinine: severe malaria and DOC for pregnant women
Artesunate – severe malaria
Primaquine: relapsing vivax or ovale malariae
Tetracycline
Doxycycline – not given to women and children (target
the bones)
Tissue schizonticides: act on pre-erythrocytic forms
Gametocytocidal drugs: destroy sexual forms of parasite
in the blood
Hypnozoitocidal/antirelapse: kill dormant forms in liver
Sporonticidal drugs: inhibit development of oocysts on gut
wall of mosquito


Early diagnosis
Prophylaxis
Use of insecticide treated nets and repellants (target
vector)
Use of larviparous fish (prevent transmission)
Use of larvicides (kill larva)
o Ex: Bacillus thuringensis (secretes toxin that kills
larva)
Health education
No clear vaccine
33
N. Villanueva
OTHER MEDICALLY IMPORTANT PROTOZOANS
INTESTINAL COCCIDIANS








Apicomplexans found in the small intestine
intracellular
Final host commonly man
Reservoir hosts: animals
Partially acid fast: possess mycolic acid

Use modified acid-fast technique (change in the staining procedure)
Infective stage: sporulated oocyst (contains sporozoites inside)
Mode of transmission: ingestion of sporulated oocyst (contaminated food and water)
Diseases primarily diarrhea or gastroenteritis
CRYPTOSPORIDIUM
Asexual and Sexual Life Cycle
Sexual and asexual cycle happens only in one host (no
intermediate hosts)
Sporulated oocyst

goes to stomach
(contains

then goes to small intestine
sporozoites which
are sausageshaped) is
ingested
Sporulated oocyst  1 sporulated oocyst = 4 sporozoites
release
 Sporozoites infect columnar cells of small
sporozoites in
intestine
small intestine
o Only target upper portion of columnar cells
o Usually only found in microvilli or brush border

Site of infection: outside cytoplasm of the cell
o extracytoplasmic
Sporozoites
 Type 1 Meront
become
o Asexual reproduction (merogony)
trophozoites then
o Contains merozoites
trophozoites
o Meront ruptures to release the merozoites
become meronts
o Merozoites infect other intestinal cells
o After many cycles, some merozoites become
Type 2 meront
 Type 2 Meront
o Sexual reproduction (sporogony/gametogony)
o Release merozoites
o Merozoites become gamonts (sexual cells)
 Macrogamont
 Macrogamont
o Microgametes and macrogametes released
 Fuse to form zygote
o Zygote eventually becomes an oocyst
(already sporulated, already has 4
sporozoites inside)
 Two types of oocyst
o Thin-walled oocyst
 Remains in small intestine
 Associated with autoinfection (deadly
among immunocompromised)
 Eventually ruptures and releases
sporozoites inside the small intestine
o Thick-walled oocyst
 This type is the one seen in the stool

34
N. Villanueva
Cryptosporidium spp.
Cryptosporidium hominis

Most common species infecting man

Formerly known as Cryptosporidium parvum antroponotic genotype (but they found out this does not usually
infect humans, usually infects animals)

Infective stage: ingestion of sporulated oocyst

Habitat: small intestine (jejunum)

Target cells: enterocytes (intestinal cells, columnar cells with microvilli, brush border)

Low infective dose (important cause of outbreak of diarrhea, ingest around 10 cysts only)

Large multiplication capability: because of the autoinfection caused by the two types of cysts
Mode of

Ingestion of sporulated oocyst
Transmission

Drink contaminated water

Swim in recreational pools that are fecally contaminated (accidentally drink the water)
Disease
Healthy Immunocompetent Patients
Manifestation

Watery diarrhea (5-10 frothy bowel movements)

Usually self-limiting (disappears in 2-3 weeks)

Important cause of outbreaks of diarrhea (can be considered as a bioterror agent)
Immunocompromised patients (AIDS patients)

Chronic diarrhea

Extraintestinal infections

Severe and life threatening

Immune system is weak, so they cannot control the parasites

Severe dehydration, electrolyte loss, excessive fluid loss

Chronic respiratory infections may also occur (pneumonia, dyspnea, bronchiolitis, chronic cough)

Cholecystitis: affecting bile ducts of the gall bladder
Pathology

Changes in the morphology of the villi
o Becomes blunted and infiltrated by inflammatory cells
o Important for absorption of nutrients
o Atrophy of villi (becomes smaller)
Diagnosis

Preferred sample: stool
o More watery: better (high detection rate)

Concentration techniques
o Sheather’s Sugar Floatation

Same principle as brine floatation

But you use sucrose solution

Better than FECT because Cryptosporidium is small (FECT involves
sedimentation)
o FECT

Fecal smear using Modified Kinyoun Method (fastest and cheapest)
o Because the organism is partially acid fast
o Modify a step in the staining procedure: the decolorizer (use 1% H2SO4 instead of 2-3%
HCl and 95% alcohol found in acid alcohol)

No more alcohol because it is strong to the organism (might kill it)
o Find circular structures that are color red
o Size of oocyst is important: 4-6 um (important diagnostic feature)

Duodenal aspirates

Enterotest

Molecular methods

Serologic tests

Fluorescent technique
Epidemiology

Found worldwide

Zoonotic infection

Implicated in outbreaks (children at risk)

Infective upon release

Highly resistant to disinfectants
o not killed by chlorination
Treatment

no standardized treatment (because if you’re healthy, it will go away after 2 weeks)

can give Nitazoxanide

immunocompromised patients: improvement of immune status

35
N. Villanueva
CYCLOSPORA CAYETANENSIS




Cyclospora cayetanensis
Species name refers to Cayetano Heredia University in Lima, Peru (where
epidemiological and taxonomic work was done)
Formerly classified as CLB (cyanobacterium like body)
Appearance almost the same as Cryptosporidium
o Bigger size: 8-10 um
Life cycle almost the same as Cryptosporidium
o Infective stage: sporulated oocyst
o Slight change in morphology of sporulated oocyst (presence of
sporocyst)
o Sporocyst: contains 2 sporozoites inside
o 4 sporozoites in 1 oocyst
o Oocyst released is unsporulated (not infective)
o Morula formation: undeveloped/undifferentiated structures inside the
unsporulated oocyst
o Sporulation happens in the environment (5-10 days)
Mode of transmission



Disease manifestation




Diagnosis



Epidemiology
Treatment






Ingestion of sporulated oocyst
Drinking/eating contaminated food and water
Associated with eating salads, strawberries, raspberries, basils, vegetables, fruits (raw and not
thoroughly washed)
Intermittent watery diarrhea
Development of d-xylose malabsorption
Usually self-limiting
Some cases: can become a chronic type of diarrhea
o Now being considered as an emerging cause of diarrhea
Only infects humans (no animal reservoirs, more easily controlled)
Same with Cryptosporidium (Also stain using modified kinyoun method)
o 8-10 um size (larger)
Fluorescence microscopy
o Capable of autofluorescence (blue or green, depends on wavelength used)
Safranin staining
Microwave heating (preparation of the smears)
Oocysts not infective once released (unsporulated)
Implicated in outbreaks of diarrhea (ingestion of fecally contaminated raspberries, basil
leaves, and other leafy vegetables)
Self-limiting (no need for treatment)
Co-trimoxazole (sulfamethoxazole-trimethoprim)
36
N. Villanueva
CYSTOISOSPORA BELLI





Cystoisospora belli
Formerly known as Isospora belli
Least common infecting man
Largest oocyst
Infective stage: sporulated oocysts
o Oval-shaped, 2 sporocysts with 4 sporozoites each (total of 8 sporozoites
per sporulated oocyst)
Life cycle almost the same with Cryptosporidium
o Release unsporulated oocyst
o Sporoblasts: undifferentiated structures inside
o 48 hours for sporulation to take place in the environment
Mode of transmission
Disease Manifestation and
Pathogenesis
Diagnosis
Epidemiology
Treatment

Oral-fecal

Intermittent diarrhea

Infects intestinal cells of humans (duodenum)

Usually asymptomatic

Diarrhea with fever, malaise, anorexia, abdominal pain, and flatulence

Seen in immunocompromised patients

Similar to cryptosporidium

Entero-test

Duodenal aspirates

More common among children, AIDS patients, MSMs
Trimethoprim-Sulfamethoxazole
TISSUE COCCIDIANS
TOXOPLASMA GONDII
37
N. Villanueva
Cats eat intermediate hosts (rats, small
animals with tissue cysts)
Oocyst from zygote
Sporulation in environment
Accidentally ingest sporulated oocyst
Life Cycle in Cats

Tissue cysts contain bradyzoites

Sexual and asexual cycle in the small intestine

Oocyst: shed in feces (Unsporulated)

3-5 days

Sporulated oocyst: 2 sporocysts with 4 sporozoites each (total of 8 per oocyst)
Life Cycle in Humans and other animals

Oocyst will become tissue cysts

Life cycle will not completely happen in humans

Oocysts never found in humans
Toxoplasma gondii
Parasite of cats
Complete life cycle happens in cats
Humans: intermediate host only (accidental)
o We can also be dead-end host (life cycle stops once in our bodies)

Infective stage: sporulated oocyst or tissue cysts
Mode of transmission

Ingestion of sporulated oocyst or tissue cysts
o Oocyst: ingestion of cat feces
o Tissue cysts: ingestion of contaminated meat (can be rat meat, undercooked, raw
meat), organ transplants

Eating contaminated food/drink with feces of cat

Vertical transmission (especially if mom is infected during pregnancy

Eating cats (possible)
Diagnostic stage
Tissue cysts

Bradyzoites
o Multiply slowly
o Develop mostly in neural and muscular tissues
o May also develop in visceral organs
o Late stages of infection
o Enclosed in a tissue cyst

Tachyzoites
o Rapidly multiply
o Infect cells of the intermediate hosts and non-intestinal epithelial cells of cats
o Found in early stages of infection
o Crescent-shaped
Disease manifestation and

Infections are usually asymptomatic (in immunocompetent individuals)
Pathogenesis
o May exhibit flu-like symptoms
o People: almost all of us are actually exposed or positive for the parasite

Most people would have antibodies against Toxoplasma

Immunocompromised patients (AIDS patients)
o Lead to encephalitis
o Formation of multifocal brain lesions
o May lead to blindness (can affect the eyes)
o Retinochoroiditis
o Lymphadenopathy
o Splenomegaly

Ocular infections (chorioretinitis)

Transplant patients: multiorgan failure

Congenital infections
o Stillbirth, abortion
o Triad of toxoplasmosis (if baby lives)

Hydrocephalus

Chorioretinitis

Intracranial calcification (calcium deposits on brain)
o Microcephaly may also occur
o TORCH Test (screening during pregnancy)

Toxoplasmosis

Other infections (coxsackievirus, chickenpox, chlamydia, HIV, human Tlymphotropic virus, syphilis)

Rubella



38
N. Villanueva
Pathogenesis
Diagnosis
Epidemiology
Treatment
Prevention

Cytomegalovirus

Herpes simplex

Obligate intracellular parasites (invade nucleated cells including macrophages)

infected cells rupture leading to dissemination

mostly asymptomatic among healthy people (because of humoral and cell mediated
immunity)

usually biopsy
o examine tissues and look for bradyzoites and tachyzoites
o difficult and invasive

preferred method: Serology
o detect antibodies
o Sabin-Feldman Test (uses methylene blue, most important, classic method)

Sensitive and specific

Specimen: serum sample

Reagent: Live Toxoplasma

Mix serum with Live Toxoplasma, antibodies in the sample will form
immune complexes with the reagent

Add methylene blue (complex prevents binding of methylene blue)

Positive result: non-uptake of the dye (colorless)

Negative result: blue color

Titer: highest solution of antibody

High titer: >1024 indicates acute infection
o Enzyme immunoassay
o Hemagglutination test
o FAT
o TORCH testing

Culture: use of vero cell lines and test animals
o Test animals: mice, gold hamster (gerbil, infect them and if they develop the
disease, the person is positive)

Examination of giemsa stained tissue sections or imprints

Examination of CSF smears, buffy coat smears

Molecular methods

Worldwide distribution (majority are seropositive)

People at risk of severe toxoplasmosis
o Infants born to exposed mothers (during pregnancy)
o Immunocompromised
Pyrimethamine and Sulfadiazine

Thoroughly cook meat

Proper hygiene

Disinfect and clean daily cat litter pans

Pregnant women: avoid cats

Avoid cats
SARCOCYSTIS SPP.
In final host,
sarcocyst
releases zoites
Sporulated oocyst
released in feces
Sporozoites form
merozoites
Sexual Cycle

Zoites infect and produce
gametes (microgametes and
macrogametes)

Zygote formed

Zygote forms oocyst
(sporulated in human host)

Sporulated oocyst: contains
2 sporocysts, each with 4
sporozoites (total of 8)

Ingested by intermediate
host
Asexual Cycle

Merozoites form 2nd and 3rd
generation meronts

Meronts form sarcocyst
39
N. Villanueva
Sarcocystis spp.
Infects a wide variety of animals and sometimes humans
S. hominis: involves cattle
S. suihominis: involves pigs (-suis: related to pigs)
Final host: humans
Intermediate hosts: pigs and cattle
Infective stage to final host: sarcocyst (tissue cysts found in muscle and tissues of pigs and cattle)
o Sarcocysts contain zoites

Man can sometimes be an intermediate host (accidentally ingest sporulated oocyst)
o Dead-end host
Mode of transmission

Ingestion of infected meat
Disease
Sarcosporidiosis or Sarcocystosis

Invasive form (rare)
o Accidentally ingest sporulated oocyst
o Vasculitis
o Myositis: inflammation of heart muscle
o If we become intermediate host

Intestinal form (more common)
o Human: final host
o Nausea, abdominal pain, and diarrhea
o Usually mild, less severe (for 48 hours lang)
o Self-limiting

Other manifestations
o Acute fever, myalgia, bronchospasm, elevated ESR, elevated Creatine Kinase enzyme
(elevated in muscle pain), symptoms may last up to 5 years
Diagnosis

muscle biopsy (definitive diagnosis)
o sarcocysts: microscopic in cattle (S. hominis)
o sarcocysts: macroscopic in pigs (S. suihominis)

stain: H&E; PAS (confirmatory)

stool exam: detection of sporocyst
o concentration methods: floatation

PCR
Treatment

Rarely required (because asymptomatic)

May use albendazole, metronidazole, co-trimoxazole
Prevention

rare in humans

thorough cooking of meat

freezing of meat (low temp kills sarcocysts)






HEMOFLAGELLATES (BLOOD AND TISSUE FLAGELLATES)


Flagellates found in blood, tissues, and CSF
Medically important genera: Trypanosoma and
Leishmania (only these two infect humans)
Epimastigote



Trypomastigote


FOUR MORPHOLOGICAL FORMS
Amastigote
Promastigote
 Also called Donovan Leishman Body
 Oval-shaped
 Has the following structures:
o Nucleus
o Kinetoplast (anterior to nucleus)
o axoneme
o Basal body
o Has no flagella
 Intracellular stage (inside the host cell)

Also called Leptomonas

More elongated and longer

Has the following structures:
o Kinetoplast (still located anterior
to nucleus)
o Basal body
o Axoneme

o 1 anterior flagella
Also called Crithidia
Elongated, wider than promastigote
Structures:
o Nucleus
o Kinetoplast (still located
anterior to nucleus)
o 1 anterior flagellum
o Undulating membrane (1/2
body length)
Also called Trypanosome
Elongated, but with different forms
o C-shape and U-shape
Structures
o Nucleus
o Flagellum
o Undulating membrane (full
body length)
o Kinetoplast (located posterior
to nucleus)
o Presence of metachromatic
granules (Volutin granules)
40
N. Villanueva
TRYPANOSOMA
TRYPANOSOMA CRUZI
Triatomine bug
takes a blood
meal
Triatomine bug
defecates on
the wound
Metacyclic
trypomastigote
penetrates
different kinds
of cells
Host cells
release
amastigotes
Triatomine bug
bites human
In midgut of
triatomine bug
In hindgut of
triatomine bug
Human Stages
Triatomine bug
Female
Also known as Assassin bug
Bites during the night
Also known as kissing bug because they
prefer to bite in mucosal areas or in the lips
 Infective stage to humans: feces of the bug
o Metacyclic trypomastigote
o Feces enters bite wound (it is not injected)
 Metacyclic trypomastigote becomes an
amastigote inside host cells
 Amastigotes reproduce asexually (binary
fission)

o
o
o
o
 Amastigotes transform into trypomastigotes
(diagnostic stage)
 Enter the bloodstream
 Trypomastigotes infect other host cells
 Become amastigotes again inside the host
cells
 Clinical manifestations can arise from this
cycle
Triatomine Bug Stages
 Acquires trypomastigote (infective stage to
the bug)
 Trypomastigotes become epimastigotes
(via longitudinal fission)
 Multiply
 Epimastigotes become metacyclic
trypomastigotes
 Fast transformation
o That’s why promastigote sometimes not
presented (but the stages happen in the
insect)
 Triatomine bug bites human, transfers
metacyclic trypomastigotes via feces
 Amastigote in tissue specimens:
intracellular
 Trypomastigote in blood: extracellular
Trypanosoma cruzi
All four morphological forms are found
Belongs to Trypanosome Group Stercoraria
Primarily infects: myocytes, heart cells, and RESs (reticuloendothelial system: monocytes, macrophages, skin, gonads,
intestinal mucosa, placenta etc., so it is intracellular)

Causes Chagas’ Disease (Dr. Chagas first to study the disease) or American Trypanosomiasis (because of high prevalence
in America)

Found in the PH (but no cases)
o Found in squalid areas or dirty areas, mud walls

Infective stage to humans: metacyclic trypomastigote

Multiply within the mammalian host in a discontinuous manner

Zoonotic mammalian reservoir hosts: domestic animals, armadillos, raccoons, rodents, marsupials, and some primates
Mode of transmission

Feces of vector entering bite wound

Blood transfusion

Transplacental (vertical, can cross placenta during pregnancy)

Transmission associated with poor living conditions
Final Host
Humans



41
N. Villanueva
Intermediate
host/Vector
Disease Manifestation
Pathogenesis
Diagnosis
Epidemiology
Reduviid Bug/Kissing bug (Triatoma, Panstrongylus, Rhodnius)
Acute phase (Initial)

Fever and lymphadenopathy (enlargement of lymph nodes near the chagoma)

Diffuse or focal inflammation (affecting myocardium)

Malaise

Nausea

Vomiting

Chagoma: local inflammation, reddish nodule, furuncle-like lesions associated with central
edema, regional lymphadenopathy (at site of bite wound)

Romaῆa’s sign: periorbital swelling (edema of eyelid and conjunctiva) parasite penetrates the
conjunctiva, unilateral swelling (only one eyelid affected), bipalpebral edema, conjunctivitis

after a few months, symptoms disappear (latent phase)
Chronic Phase (after 10-20 years)

no characteristic symptoms

during this phase, still capable of transmitting it to other people

amastigotes still reproducing
o triggers enlargement of vital organs
o fibrotic reactions that can cause injury to the myocardium, cardiac conduction network,
and enteric nervous system (decrease in nerve ganglia, leading to megasyndromes)
o congestive heart failure
o thromboembolism
o chest pain, palpitations, dizziness, syncopal episodes, abnormal ECG findings
o mega colon (chronic constipation)
o mega cardium/cardiomegaly (can develop arrhythmias and you can die)
o mega esophagus (achalasia)
*majority of symptomatic chronic patients manifest with the cardiac form, rest with gastrointestinal form

acute inflammatory reaction on bite (Chagoma)

uses lectin like carbohydrates for binding

target cells: cells of RES, cardiac cells, skeletal and smooth muscles, neuroglia cells

complete patient history
o determine possible exposure, risk factors, recent transfusion, contact
o primary tool

presence of lesions (in early phases)
o aspirate, prepare a smear, stain, then view

cardiac symptoms present, especially if living in endemic regions

demonstration of trypanosomes in:
o blood (thick and thin smears) for sdefinitive diagnosis
o buffy coat (concentration technique: Strout Method), can see trypomastigote and
sometimes the amastigote
o CSF
o Tissues (can see amastigotes)
o Lymph
o Trypomastigotes only seen in first two months of acute disease

Concentration methods (microhematocrit)

PCR

Cardiac form
o ECG and echocardiography (may show atrial fibrillation/flutter, low QRS voltage, dilated
cardiomyopathy, and tricuspid and mitral regurgitation)

Intestinal form
o Barium esophagogram (esophageal dilation)
o Barium enema (megacolon of the sigmoid and rectum)

Xenodiagnoses
o Use of kissing bug (make the bug bite you)
o If parasite develops inside, then you are infected

Culture: Chang’s, NNN

Serology: IFAT, Complement Fixation (Guerreiro Machado Test), ELISA, Western Blot, IHA (for
chronic phase)
o WHO recommends using at least two techniques with concurrent positive results before
making a diagnosis of Chagas disease

Occurs only in the American continent

Highest prevalence in Brazil

More common in rural areas (because they prefer squalid conditions, mudwalls)
42
N. Villanueva
Treatment
Prevention


Vector

Chronic disease more common

Common in unsanitary housing conditions
Nifurtimox and Benznidazole
*symptom-specific management

Vector control

Screening of blood

Health education
Trypanosoma rangeli
Nonpathogenic
Metacyclic trypomastigote is discharged via the salivary glands
o Injected
o Not in the feces

Rhodnius
TRYPANOSOMA BRUCEI COMPLEX
Tsetse fly bites
human
Injected
metacyclic
trypomastigotes
transform into
bloodstream
trypomastigotes
(diagnostic stage)
Trypomastigotes
found in blood
Tsetse fly’s
midgut
Procyclic
trypomastigotes
leave midgut
Epimastigotes go
to salivary glands
Human stages

Takes a blood meal

Injects metacyclic
trypomastigotes

Goes to different parts of the
body (brain and other vital
organs)

Trypomastigotes multiply
(binary fission) in various
body fluids (blood, lymph,
spinal fluid)

Tsetse fly bites human,
acquires the trypomastigotes
Tsetse fly stages

Trypomastigotes become
procyclic trypomastigotes

Procyclic trypomastigotes
multiply by binary fission

Transform into epimastigotes



They multiply here
Transform into metacyclic
trypomastigotes
Tsetse fly bites human and
injects the metacyclic
trypomastigotes
Trypanosoma brucei complex
Complex because it is made of two subspecies
o Rhodesiense
o Gambiense
o Belong to trypanosome family Salivaria
o Morphologically the same, different in location (endemic area – area where it is transmitted) and severity of
infection

T. brucei brucei: primarily affects wild and domestic animals

infective stage to humans: metacyclic trypomastigote

only epimastigote and trypomastigote are seen
o epimastigote in insect vector
o trypomastigote in human (diagnostic stage)

polymorphic (slender, short, and stumpy forms)

trypanosomes evade immune detection through antigenic variation (VSGs)
Mode of transmission
Insect bite
*can also be through mechanical methods (accidental needle pricks), other blood-sucking insects,
vertical transmission
Intermediate Host/Vector
Tsetse Fly (Glossina spp.)

43
Final Host
Disease Manifestation
Pathogenesis
Diagnosis
N. Villanueva
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T. b. rhodesiense – G. pallidipes, G morsitans

T. b. gambiense – G. palparis
*has animal reservoir hosts
Human
Trypanosoma brucei gambiense (95% of cases)
 West and Central Africa (endemic area)
 No animal reservoir hosts involved (anthroponotic, only humans, rural population)
 low parasitemia
 Causes Gambian or West African Sleeping Sickness
o Has a slower progression (more than 9 months – year)
o Less severe type
 Earliest sign: Trypanosomal Chancre
o Painful ulceration at site of bite
o Patients still appear healthy, but trypomastigotes already seen in the blood smear
o Parasite goes to other body parts, patient may experience fever once the lymph nodes are
affected
 Lymphadenopathy (affects axillary and supraclavicular lymph nodes in both gambiense and
rhodesiense)
 Winterbottom’s Sign (affecting the cervical lymph node, its as big as a plum)
o Other manifestations: malaise, weakness, night sweats, dizziness, and nausea
 Chronic disease
o CNS invasion (goes to the brain)
o Sleeping sickness stage initiated
o Prominent lympadenopathy
o Severe headache, increasing mental deterioration and apathy, meningoencephalitis
 Manifestation of Kerandel’s Sign (delayed sensation to pain) and Kernig’s Sign (inability to
straighten leg when hip is flexed at 90 degrees)
o Terminal phase: coma leading to death
Trypanosoma brucei rhodesiense (5% of cases)
 East and South Africa (endemic area)
 Causes Rhodesian or East African Sleeping Sickness
 Many reservoir hosts (anthropozoonotic), game parks ->wild game animals, domestic animals
such as sheep and ox
 High parasitemia
 Similar to Gambian sleeping sickness
o But acute and rapidly progressing
o Dead in less 9 months
o CNS stage takes place in the early stages
o Glomerulonephritis may also be seen
 Because of formation of immune complexes
 Antigens bind to antibodies and complexes are deposited to the kidney
o Minimal lymphadenopathy
*both types: early stages are called hemolymphatic stages, late stages are called
meningoencephalitic stage

Generalized lymphoid hyperplasia (increase in number of cells in lymph nodes)

Anemia (blood loss)

Thrombocytopenia

Hypergammaglobulinemia (increased antibody production)

Immune evasion through VSGs

Acute infection for Rhodesian

Chronic infection for Gambian
 Physical findings and patient history
 Demonstration of trypomastigotes in blood, CSF, lymph node aspirate
o Early stages, examine blood for trypomastigotes
o If sleeping stage has started, examine CSF
o More useful for rhodesiense because of high parasitemia
o Abnormal CSF: increase in cell count, opening pressure, protein concentration, and IgM levels
(increase in IgM levels are pathognomonic for the meningoencephalitic stage)

Concentration of buffy coat (Giemsa stain), recommended for low parasitemia

Serology (IHAT, ELISA, Rapid tests, immunofluorescence)

Mini-anion exchange centrifugation technique

PCR

Molecular methods

Animal inoculation and culture
44
N. Villanueva
Epidemiology
Treatment
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Card agglutination test (CATT)
Vectors inhabit areas near river banks and streams
Congenital transmission is possible
Low prevalence rate (<1%)
Better prognosis if treatment started before CNS stage
Pentamidine and Suramin (for blood and lymphatic stage)
Melarsoprol (Late stage)
o Can cause Jarisch-Herxheimer reaction (due to trypanosome lysis)
Nitrofurazone used in case of Melarsoprol failure
LEISHMANIA
Sandflies bite human
Promastigotes
ingested/phagocytized
by macrophages in the
blood
Macrophages burst
Sandflies bite human
In midgut of sandfly
Amastigote migrate to
proboscis
Human stages

Injects promastigote into the skin

Promastigotes become
amastigotes inside the
macrophage

Amastigotes multiply inside

Release amastigotes

Amastigotes: infective stage to
sandflies
Sandfly stages

Ingests macrophages infected
with amastigotes

Amastigotes transform into
promastigotes

Amastigotes divide in the midgut

When it bites a human, it injects
the promastigotes
Leishmania spp.
Vector borne parasitic disease
o Sandflies: Phlebotomus spp. (infects old world, Europe), Lutzomyia (infects new world, US)

Intracellular parasites (inside host cells)

Diploid protozoa

Zoonotic (dogs in urban places, rodents in urban and rural places)

Old World Leishmaniasis: L. tropica (Asia and Eastern Europe), L. aethiopica (Africa), L.major

New World Leishmaniasis (Mexico, Central America, South America, Amazon rainforest): L. mexicana, L. amazonensis,
L. guyanensis, L. braziliensis, L. chagasi

Leishmania tropica

Leishmania braziliensis

Leishmania donovani (most severe)

Infective stage to humans: promastigotes

Infective stage to sandflies: amastigotes

Targets RE cells

Viannia subgenus produces promastigotes in the hindgut, midgut, and proboscis (Leishmania subgenera only produces
promastigoes in the midgut and proboscis)
Mode of transmission

Bite of vector

Blood transfusion

Close contact

Contamination of bite wounds
Intermediate host/Vector
Sandflies
Final Host
Humans
Disease Manifestation:

Also known as Old World Leishmaniasis, Aleppo Button, Delhi Boil, Baghdad Boil, Jericho Boil
Cutaneous

Etiologic agent: Leishmania tropica (can also be caused by L. major and L. mexicana)
Leishmaniasis
o Live in skin capillaries (in the endothelial cells)
o That’s why they’re seen as lesions on the skin
o L. tropica: dry or urban oriental sore
o L. major: moist or rural oriental sore
o L. mexicana: chiclero ulcer

Incubation period: weeks to months

45

Diffuse Cutaneous
Leishmaniasis
Disease Manifestation:
Mucocutaneous
Leishmaniasis
Disease Manifestation:
Visceral Leishmaniasis
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Epidemiology

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
Diagnosis

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Treatment
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N. Villanueva
Painless elevated skin ulcers
o Leaves an ugly scar and is highly disfiguring (erodes the skin)
o Oriental Button: erythematous papule which forms an ulcer
Common in Middle East and some parts of Asia
AKA Anergic or Lepromatous Leishmaniasis
Characterized by a localized, non-ulcerating papule
Develops diffuse satellite lesions (affects the face and extremities)
May be initially diagnosed as lepromatous leprosy
Also known as American, New World Leishmaniasis
Etiologic agent: Leishmania braziliensis
Incubation period: weeks to months
Habitat: tissues in nose and mucous membranes
Initial: ulcers are similar to Cutaneous Leishmaniasis
Later stage: spreads to oronasal and pharyngeal mucosa (can lead to dysphonia, dysphagia,
and aspiration pneumonia)
o Involvement of the mucous membranes results in nasal stuffiness, discharge,
epistaxis, and destruction of the nasal septum
o Espundia: in the nose
o Tapir Nose: also affects the nose
o Chiclero Ulcer: affects ears
Also known as Kala-azar, Dumdum Fever (this is a place), Black Fever
Etiologic agent: Leishmania donovani (can also be caused by L. chagasi and L. infantum)
Incubation period: 1-3 months
Habitat: RES
Dromedary fever peak: fever with twice daily elevations (Double Quotidian)
Splenomegaly
Cachexia
Reticuloendotheliosis
Hepatomegaly
Darkening of skin (forehead, temples, around the mouth)
o That’s why its called black fever
Dermal leishmanoid lesions (rare)
o Present if treatment is incomplete
Post-kala azar dermal leishmaniasis (PKDL): sequela
o Cutaneous eruption resulting in hypopigmented macules, malar erythema, nodules,
and ulcerations
o Manifest a few months to several years after treatment
Endemic in 88 countries on 5 continents
Visceral Leishmaniasis
o Bangladesh, Brazil, India, Nepal, and Sudan
Cutaneous Leishmaniasis
o Afghanistan, Brazil, Iran, Peru, Saudi Arabia, Syria
Mucocutaneous Leishmaniasis
o Brazil, Eastern Peru, Bolivia, Paraguay, Ecuador, Colombia, Venezuela
Demonstration of lesions
Tissue biopsies (for amastigotes)
Skin biopsies (for amastigotes)
Animal inoculation
Examination of bone marrow, spleen, lymph node (also for amastigotes)
Montenegro Skin Test
o Also called Leishmanin Skin Test
o Test to determine if you have a previous exposure to the parasite
o Person injected with a suspension of parasites (promastigote) in the intradermal area
o Positive result: if there is enlargement
o Negative in diffuse cutaneous leishmaniasis and kala azar
Formol Gel Test
o Useful for donovani
o To determine if there is hypergammaglobulinemia
Serology: IFAT, ELISA, rk39 antigen dipstick test
Culture: NNN (Schneider’s medium also found useful)
Molecular methods
Antimony compounds (sodium stibogluconate, n-methyl-glucamine antimonite or meglumine)
46
N. Villanueva
BABESIA
Sporozoites
infect RBCs
Merozoites
released from
RBCs
Gametogony
Transmission of
gametocytes
Gut/GI Tract
Formation of
ookinete
Oocyst bursts
Erythrocytic cycle
 start of erythrocytic schizogony
 no exo-erythrocytic cycle in Babesia spp.
 sporozoites develop into an immature
trophozoite form
 trophozoites develop into merozoites

infects other RBCs
 after many cycles, gametes are produced
(macrogamete and microgamete)
 no schizonts and gametocytes
 gamete is ingested by another tick
 gamete: infective stage to the definitive host
Sporogonic cycle
 macrogamete and microgamete fuse to form
zygote
 fertilization
 zygote becomes elongated and motile
o forms ookinete
o subsequent development of Babesia:
development of numerous kinetes
(sporokinetes)
 when sporokinetes are released, they
continue to infect and multiply in
various organs and the ovaries, until
death ensues
 ookinete enters salivary gland
 ookinete develops into an oocyst
o sac-like structures with sporozoites

releases sporozoites

already in the salivary glands
Babesia spp.
 Blood-borne and vector-borne
o Transmitted by ticks (genus Ixodes)

Ixodidae or hard ticks

Transmission via soft tick (Ornithodoros erraticus) has been reported

Other vectors: Boophilus spp., Rhipicephalus spp., Hyalomma spp., Haemaphysalis spp., and Dermacentor spp.
 Hemosporidian parasites
 Dr. Victor Babes: first documented Babesia in cattle (1888)
 Heteroxenous parasite: infesting more than one kind of host, requiring at least two kinds of host to complete the life cycle
(mammal as primary host and ticks as intermediate hosts or vectors)
 has a tendency to take on pleomorphic forms (ability to alter their shape or size in response to environmental conditions) in
different hosts
o obscures their identification at the species level
 transstadial: capable of stage-to-stage passage
o each of developmental stages capable of parasite transmission to mammals
 smaller forms (ex: Babesia bovis and Babesia equi more pathogenic
 larger forms (ex: Babesia bigemina and Babesia caballi) less virulent
 Sometimes mistaken for Plasmodium
o Important to differentiate them
o Babesia: blood parasite that causes malaria-like infections
o Babesia does not undergo exoerythrocytic merogony (residual bodies usually not found in infected RBCs)
 Zoonotic infection
 Causative agents: Babesia microti (found in the Northeastern US) and Babesia divergens (found in Europe)
o Groupings obtained through phylogenetic analyses of gene sequences of SSU rDNA (small subunit ribosomal
deoxyribonucleic acid) of Babesia spp.
Mode of

Bite of an infected tick (blood meal)
Transmission

Blood transfusion
47
N. Villanueva
Vertical transmission
Organ transplant
Transovarian transmission (for Babesia divergens)
o Ticks can pass the parasite to its progeny/offspring
o Infect ova (egg) of the ticks
o Terminates with death of the vector
Tick (Ixodes)
Mammals

White footed mouse (most important)

livestock

Cattle

Humans (accidental intermediate host only, because this is primarily a zoonotic infection)

Deer: primary reservoir host
Infective stage to intermediate hosts: sporozoites (called pyriform bodies)
Similar to malarial parasites

But no schizonts or gametocytes

Up to four trophozoites found in each cell (sometimes mistaken as Falciparum)

Presence of up to four merozoites
o Maltese Cross Arrangement (four merozoites)
o Bunny Ears/Rabbit Ears Appearance (two merozoites)

Causes Babesiosis, Piroplasmosis, Nantucket Fever, Splenic Fever, Redwater Fever, Tick fever,
or Texas Cattle Fever (first identified among cattle)

Most cases are asymptomatic and usually self-limiting
o Healthy people have no symptoms (if ever there is, it is only mild and self-limiting)
o In low-grade and chronic infections

Incubation period: 1-12 months (wide range)

No paroxysmal cycle

1-6 weeks postexposure: fatigue, malaise, anorexia, and weight loss
o Followed by nonperiodic intermittent fever, chills, sweats, headache, myalgia, arthalgia,
nausea, vomiting, and prostration

Signs and symptoms mimic malaria
o Mild chills and fever
o Hemolytic anemia

With hemoglobinuria, jaundice, pulmonary edema in severe cases
o Jaundice
o Hepatomegaly
o Hepatosplenomegaly (because lots of RBCs are destroyed, and they go to the spleen)

Patient may also manifest emotional lability, depression and hyperesthesia

Most people have no problem with this (immunocompetent)

Affects primarily the elderly, immunocompromised, splenectomized patients (those that underwent
splenectomy, because they cannot remove defective RBCs)

Co-infection with Borrelia burgdorferi (Lyme disease)
o Both share same tick/vector
o Same endemic area
o Same manifestations

Both innate and acquired immunity contribute to resolution of the primary infection (provide
protection against subsequent exposures)

Blood smears: for acute infections only

Examination of Giemsa stained smears
o Definitive diagnosis
o Shows unique morphological features

Parasite dimensions and pleomorphisms are noted
o Ring form, pear-shaped, Maltese cross or tetrad form
o Need to be ascertained (with absence of pigment in infected RBCs)
o To rule out misdiagnosis from Plasmodium and Lyme disease

Serology
o IFAT (diagnostic titer or amount of antibody present = 1:64)

Indirect fluorescent antibody test

Serological method for confirming the identity of viral isolates
o Immunofluorescent assay (IFA)

Widely used in acute cases and epidemiological studies
o Inoculation of animals (Gold hamster or gerbil)

If the animal dies or gets the disease, then they test positive

For cases of low parasitemia



Definitive Host
Intermediate Host
Morphology
Disease
Manifestation and
Pathogenesis
Risk Factors
Immunity
Diagnosis
48
N. Villanueva
In cases of low-grade infection or parasitemia
Serum dilution

To rule out possible cross-reactions

History of tick bite

Molecular methods (sensitive but expensive)
o In cases of low-grade infection or parasitemia
o PCR: gold standard for Babesia detection

Zoonotic

Reported in Europe, North East North America, and also in the West Coast

Human infections usually occur during spring or summer

Affects farmers living in close habitation with livestock and wild animals

No human infections reported yet in PH (but there are animal cases)

Epidemiologic data useful for low-grade infection or parasitemia

B. microti and B. divergens
o Third grouping: the WA1-type in Western US (tentatively grouped with B. microti or with
Theleria spp.)

Recently in Italy and Austria: parasites revealed SSU rDNA sequences more closely related to B.
odocoileus (species has morphological, molecular, and immunological similarities to B. divergens)

Combination of Clindamycin and Quinine

Or Azithromycin and atovaquone

For B. equi and B. caballi in vitro
o Use arteminisin, pyrimethamine, and pamaquine
Avoid tick bites
Apply insect repellants
Screen blood donors
Remain covered with clothing
Immediately remove any attached ticks
Control rodent population (since they are major carriers or reservoirs)
o
o
Epidemiology
Treatment
Prevention
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MICROSPORIDIA
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Obligate intracellular parasites
Phylum Microspora
Possess polar tubules/filaments
Usually seen in immunocompromised patients (AIDS)
Target enterocytes (intestinal cells)
Reproduce by binary or multiple fission, spore formation
Now classified as a fungi
Uses polar tubules to inject the infective stage in you
Most prevalent: Encephalitozoon bieneusi
49
N. Villanueva
NEMATODES
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Phylum Aschelminthes
Roundworms
Bilaterally symmetrical
o if you divide them in the center, the appearance will
be equal on the left and on the right
non-segmented (no lines), cylindrical in shape
presence of pseudocoel (body cavity)
cuticle: protective covering
o made of chitin (chitinous nature)
complete digestive system
o mouth: contains lips, teeth, or hooks (depends on
species)
o buccal cavity
o esophagus: muscular, bulb-like structure at the end
o pharynx: muscular, triradiate symmetry
o intestines
o rectum
o anus: release of waste materials
Reproductive structures – tubular and coiled
o Males: spicule (for copulation), copulatory bursa
(can be seen in hookworms)

Testes, vas deferens, seminal vesicle,
ejaculatory duct (lined with prostate or cement
glands), gubernaculum (accessory copulatory
apparatus)
o Females: uterus (contains the eggs), vagina, ovaries,
oviduct
no circulatory system
may be free-living or parasitic, or both




reproduction: may be oviparous, ovoviviparous,
larviparous
chemoreceptors: amphids and phasmids
o nervous system of the worm
o found on head and tail portion
o cephalic: head; caudal: tail

amphids: head/cephalic

phasmids: tail/caudal
o all nematodes have amphids
o phasmid worm (Class Phasmidia/Secernentia)

almost all medically important parasites are
phasmids
o aphasmid worm (Class Aphasmidia/Adenophorea)

Ex: Trichuris, Trichinella, Capillaria
Dioecious (male and female parasite)
Stages
o Adult,larval, and egg/ovum stages
o Larva (L1-L4) – molting stages

Filariform larva: possess uniform muscular
esophagus, usually L3

Rhabditiform larva: possess expanded and
bulb-like posterior esophagus, usually L1
o Microfilaria – stage found in some parasites

Usually in life cycles of filarial worms

Specialized type of egg

Pre-rhabditoid stage
ASCARIS LUMBRICOIDES
Ingestion of embryonated egg
Larva undergoes heart-lung
migration
Becomes adult worm in small
intestine
Egg should find its way to the
soil in order to become
embryonated
*preferred soil is loamy (+moist
environment)
Life Cycle

Goes to stomach then to the small
intestine

Larva emerges from the egg

Larva penetrate small intestine, goes
to heart and lungs

Important for the development of the
parasite

After migration, goes back to
esophagus to be swallowed back into
the small intestine

Undergo sexual reproduction
(produce eggs)

Unembryonated eggs found in stool
sample

Embryonation in the soil takes 2-3
weeks
*if parasite undergoes heart-lung migration, life
cycle is classified as an indirect life cycle
50
N. Villanueva
Ascaris lumbricoides

Common name: Giant Intestinal Roundworm

Infective stage: embryonated egg

Ascaris of humans (primarily infects humans only)
o No known reservoir hosts

Habitat: small intestine

Final host: man

Soil-transmitted helminth

Normal life span: 1 – 2 years

Do not multiply in the small intestine

Polymyarian (arrangement of somatic muscles)
o Cells are numerous and project well into the body cavity
Mode of

Ingestion
transmission

Oro-fecal route
Adult worms

Trilobate/triradiate lips
o 1 dorsal and 2 (ventrolateral)

Adults possess structures to protect themselves
o PI-3 (Pepsin inhibitor 3)

To protect against digestion of stomach (to prevent being digested by stomach)
o Phosphorylcholine

Suppress lymphocyte proliferation

Females
o Capable of laying 200k eggs
o Have paired reproductive organs in the posterior two-thirds

Males
o Have two spicules (also used for holding the female during copulation)
o Smooth striated cuticles
o Single, long, tortuous tubule
Types of Eggs
Unfertilized Corticated

Oval-shape

Structures inside: coarse lecithin granules

Glycogen layer surrounds the granules

Mamillary/albuminous coat (corticated)

Unfertilized decorticated: no mamillary coat
Fertilized Corticated

More circular

Lipoidal/vitelline layer: innermost layer
o Impermeable layer
o Encloses the amorphous mass of
protoplasm

Glycogen layer surrounds lipoidal layer

Mamillary coat

Fertilized decorticated: no mamillary coat
Pathology
(Unfertilized Corticated)
(Unfertilized Decorticated)
*embryonated eggs are never recovered in stool
samples
 Embryonation will happen in the soil (because
it is an STH)
 Eggs can embryonate when formalinized (if its
super old na)
(Fertilized Corticated)
(Fertilized Decorticated)
*larva inside in embryonated egg is L2

Host immune response

Effects of larval migration
o Lungs: triggers respiratory-like illnesses (Loeffler’s Syndrome, type of eosinophilic
pneumonitis)

Can also cause asthmatic attacks
o There will be an elevation of eosinophils (Eosinophilia)
o Presence of charcot leyden crystals
o Can also cause edema of the lips

Mechanical effect of adult worms
o Triggers irritation to small intestine (especially in heavy infections)
o Unattached parasites (just swimming in the small intestine)
51

Disease






Diagnosis






Epidemiology
Treatment







N. Villanueva
Nutritional deficiencies
o Worms compete for absorption of nutrients
o Lactose intolerance
o vitamin a malabsoprtion
Incubation period: approx. 60-75 days
Light infections: usually asymptomatic
o Some don’t even know that they have it (can only know through stool exam)
Luminal parasite
Heavy infections: appearance of symptoms
o Abdominal pain
o Vomiting
o Growth stunting (attributed to nutritional deficiency)
o Can cause intussusception (part of the intestine folds into the section next to it) or volvulus
(can result in bowel infarction and intestinal perforation)
o Intestinal spasm (leading to intestinal obstruction)

Caused by worms irritating nerve endings in mucosa
Lots of worms leads to intestinal obstruction
o worms form bolus
o may lead to intestinal perforation
worms can become erratic
o wander to other parts of the body
o triggered by high fever, stress, other illnesses, drugs
o escape through nostrils
o may be regurgitated and vomited
o inhaled into the trachea
o may invade bile ducts (through ampulla of Vater) and enter the gallbladder or liver
o Biliary Ascariasis: may experience severe colicky abdominal pain (because of movement of
worms to biliary tract)
o Appendicitis
o Pancreatitis
o Abscess (caused by intestinal bacteria being carried to migration sites)
o Acute peritonitis
o Chronic granulomatous peritonitis
more eggs ingested = heavier infection
no autoinfection
specimen for larval stage: sputum
o because of heart-lung migration of larva
specimen for eggs: stool
DFS (less sensitive)
Kato-Katz
o Quantitative diagnosis
o Intensity of helminth infection (eggs per gram, epg of stool)
Concentration Techniques
Soil transmitted helminth
More common in poor countries where sanitation is poor
Highly affected: school aged children (grades 1-3)
Eggs are highly resistant (can survive very harsh environment)
DOC: Mebendazole
Other drugs: albendazole
TRICHURIS TRICHIURA
Ingestion of
embryonated egg
Larva will crawl towards
the colon
Parasites reproduce
Unembryonated egg
goes to loamy soil
Life Cycle
Go to stomach then to small intestine
Small intestine: where larva emerge
Becomes adult in the large intestine
Attached parasites (heads are
embedded in the large intestine)

Unembryonated egg seen in the stool
sample

Maturation time: 10-14 days




52
N. Villanueva
Trichuris trichiura









Common name: Whipworm
Aka Trichocephalus trichiurius
Final host: man
Habitat: large intestine/colon
Infective stage: embryonated egg
Soil-transmitted helminth
Female produces 7k-10k eggs
No heart-lung migration
Holomyarian (based on arrangement of somatic muscles in cross-section)
o cells are small, numerous, and closely packed in a narrow zone
Mode of Transmission
Ingestion of embryonated egg
Morphology of adult worm

Whip: anterior portion is attenuated/tapered
o Where you can find the esophagus (has a string of beads appearance)

Posterior portion: robust/thick

One spicule: retractable/retractile
o Appearance: lanceolate/sword-like

Anterior portion are embedded in the large intestine
o Pin fashion manner/pin cushion manner

Male: has a retractile sheath
Morphology of egg

Lemon-shaped

Barrel-shaped

Football shaped

Japanese lantern appearance

Yellowish outer shell and transparent inner shell

Unembryonated once released (needs to embryonate in soil)

Bipolar mucus plugs: where larva goes out
(unstained, no color)

Shell is nonstriated

Color: bile-stained (dark yellow/brownish)

Larva in egg: L1
*Trichuris eggs in soil more susceptible to desiccation
Pathology

Embedded in large intestine
o Secrete TT47 (promote pore formation)
o Cause petechial hemorrhages (may predispose to amebic dysentery, ulcers provide a suitable
site for E. histolytica)
o Mucosa becomes hyperemic (excess of blood) and edematous

Enterorrhagia or intestinal bleeding is common
Disease

Patients usually asymptomatic

Heavy infections: symptomatic (5000 eggs per gram of feces)
o Diarrhea
o Trichuris dysentery syndrome

Manifested by chronic dysentery and rectal prolapse
o Blood in stool (because parasites are embedded, promote blood loss)
o Inflammation

Prolonged/chronic inflammation leads to anemia
o IDA
o Rectal prolapse (cinnamon roll appearance)

Parasite goes to rectosigmoid area and causes inflammation

Lower portion of colon becomes turned inside out and protrudes outside the body

Rectum loses its internal support due to the worms burying their heads in the intestinal
lining (loosens epithelium and weakens muscles)
o Weight loss
o Appendicitis
o Hypoalbuminemia: low albumin levels in blood because of blood loss
o Appendicitis and granuloma formation
o In children: poor appetite, wasting, stunting, and recued intellectual and cognitive
development

Due to lumen of appendix being filled with worms
Diagnosis

DFS

Kato-Katz

Concentration techniques (FECT)

FLOTAC technique
53
N. Villanueva
Epidemiology





Treatment
STH
More common in tropical areas
Common among children
DOC: Mebendazole
Albendazole, albendazole with ivermectin
ENTEROBIUS VERMICULARIS
Ingestion of
embryonated egg
Larva goes to colon
Reproduction in
large intestine
After 4-6 hours,
embryonated









Life Cycle
Go to stomach then small intestine
Small intestine: where larva hatches
Where it becomes adults
Female worm migrates to perianal area at night
o Perianal area for the oxygen requirement of
the eggs
After laying eggs, female dies
After copulation, male dies
Eggs can fall onto the bedsheet
o Egg goes to air, eggs can be inhaled
Autoinfection: scratch butt, eggs goes to hand and can
go to mouth
Retroinfection
Enterobius vermicularis
Common name: Pinworm, Seatworm, Society worm, “Tiwa”
AKA Oxyuris vermicularis
Most common helminth infection in the world
Final host: man
Habitat: large intestine
Infective stage: embryonated egg
not a soil transmitted helminth
Meromyarian (arrangement of somatic muscle)
o there are two to five cells per dorsal or ventral half
Mode of transmission

ingestion of eggs (oral)

air-borne

retroinfection: eggs hatch in perianal area, larva crawl back to large intestine

autoinfection
Morphology of adult

anterior portion: wing-like structure (cephalic alae)
worm
o chemoreceptor
o employed during migration of the worm (not fully understood)
o other references: cuticular alars

esophagus: bulb/flask shaped

male: one spicule

larva: tadpole-like
*rhabditiform larva has no cuticular expansion on the anterior end
Morphology of eggs

d-shaped

lopsided eggs

football shaped with a flattened side

embryonation after 4-6 hours

2 layers
o Albuminous layer (triple covering, for mechanical
protection)
o Lipoidal layer (for chemical protection)

Adult female lays the eggs in the perianal area (around
11,105 eggs per day)

Resistant to disinfectants but succumb to dehydration in dry air
o Moist conditions: can last up to 13 days

larva in egg: L1
Pathology
Enterobiasis or Oxyuriasis

nocturnal pruritus ani (butt is itchy at night, because that’s the time the female lays the eggs)








54
N. Villanueva

insomnia (due to being awake at night due to itchiness)

secondary bacterial infection (due to wounds)

loss of appetite

abdominal pain

weight loss

irritability

grinding of teeth

vulvovaginitis: eggs may go to vagina in females (because anal area is near to the vagina)

mild catarrhal inflammation of intestinal mucosa (due to attachment of worms)

appendicitis, endometritis, salpingitis, peritonitis, ectopic deposition of eggs may also occur

innocuous: not harmful, rarely produces any serious lesions
*Familial disease, spreads easily, everyone can be infected (everyone in the family must be treated)

Scotch tape swab

Cellulose acetate swab

Cellophane anal swab

NIH swab

Swellengrebel technique: instead of scotch tape, make use of a pestle with petrolatum or
petroleum jelly
o rolled in the area

Graham’s technique: use of a slide

Petrolatum
*at least 7 negative swabs before reporting as negative (because eggs are intermittently shed

Most common helminth infection in the world

Cosmopolitan: more common among females (locally)

Cannot be controlled by sanitary disposal of waste

DOC: Mebendazole

Albendazole

Pyrantel pamoate (secondary drug of choice)
Diagnosis
Epidemiology
Treatment
HOOKWORMS
Adult worm infects via
skin penetration (if
people walk barefooted)
From blood vessels,
worms undergo heartlung migration
In the small intestine,
they become adults
(become attached to
the small intestine)
Embryonated egg
become the
rhabditiform larva
Rhabditiform larva
develops into the
filariform larva
(usually after 7-10
days, especially with
unfavorable
conditions)



Life Cycle
Worm prefers sandy soil
Goes to the blood vessels from the skin
After, they are swallowed back into the small
intestine

Diagnostic stage: unembryonated egg (found in
stool)
o Rare to recover larva because they are
attached to the small intestine

1-2 days for egg to embryonate

egg is thin-shelled
o hyaline (clear)
o with developing blastomeres (2-8)
o blastomeres have a morula ball formation
Rhabditiform larva

L1 larva

Feeding stage (open-mouth)

Buccal capsule (mouth) is longer

Small genital primordium

Short and stout
Filariform larva

L3 larva

non-feeding stage (closed mouth)

posterior portion
o tail: pointed
o membrane is sheathed

cannot identify species based on larval
stages
55
N. Villanueva
Human Hookworms
Final host: man
Infective stage: Filariform (L3) stage
Habitat: small intestine
Mode of transmission: skin penetration
o Ancylostoma: can be through oral (eating vegetables with larvae)

Eggs are indistinguishable

Undergoes heart-lung migration

Identification of species: dental pattern/buccal cavity

Necator americanus: more common in the Philippines

Males would have the copulatory bursa (used during copulation)

They are attached parasites
o attached to lining of small intestine (that’s why they are called hookworms)

cellular immune response mediated by eosinophils, mast cells, and Th2 cells
o but still no clear evidence that host develops perpetual immunity to hookworm infection
o polyvalent IgE antibodies: suggested to provide some protective roles

Meromyarian type of somatic muscle (2-5 cells arranged per dorsal or ventral half)
Ancylostoma duodenale
Necator americanus
Common name
Old World Hookworm (Europe)

New World Hookworm

American Murderer
Adults
Larger
Smaller (cylindrical, fusiform, grayish-white)
Curvature
C shape
S shape
Color
Pinkish or creamy gray color
Grayish yellow with reddish undertone
Life Span
5-7 years
4-20 years
Dental pattern/ buccal
2 pairs of ventral teeth (inner pair is smaller)
No teeth, contains semilunar cutting plates
cavity
Buccal spears (of

Inconspicuous

Conspicuous and parallel
filariform larva)

Transverse striations on the sheath in

Conspicuous transverse striations present
the tail region
on the sheath in the tail region
Copulatory bursa

Bell-shaped

Bipartite dorsal rays
(campanate
appearance)

Tripartite dorsal
rays




Spicule
Microcytic, hypochromic
anemia caused
Eggs
Pathology
Plain and bristle-like
Barbed and fused

Causes more blood loss (because of the

Less blood loss
teeth and size of the parasite)

Bluntly rounded ends

Single thin transparent hyaline shell

Unsegmented at oviposition

Are in the two to eight cell stage of division when passed out with
fresh feces
Cutaneous Phase

Ground itch, Dew itch (allergic reaction, contact with soil, especially on a dewy morning)

Redness, inflammation, urticaria (itchiness)
o Due to the parasite releasing enzymes to break down the skin
o Antigens of the hookworm trigger the allergic reaction

Maculopapular lesions

Localized erythema
Pulmonary Phase

Wakana’s Disease (Pneumonitis)

Because of the heart-lung migration

Eosinophils are increased
Intestinal Phase

Blood loss (IDA), happens when infection is chronic, most important pathology

Abdominal Pain

Diarrhea (sometimes with blood and mucus)

Eosinophilia
56
Diagnosis
Epidemiology
Treatment
N. Villanueva

Steatorrhea
*hookworm infection usually chronic (patients rarely show acute symptoms)
*Hypoalbuminemia – low level of albumin due to combined loss of blood, lymph, and protein (other
symptoms: exertional dyspnea, weakness, dizziness, lassitude, rapid pulse, edema, and albuminuria)

DFS (only when infection is heavy)

Kato-Katz (not recommended because hookworm eggs are thin-shelled)
o Shell will disintegrate easily (will give a false negative result)

Concentration Techniques (Zinc sulfate centrifugal flotation, FECT)
o Use greater amount of stool (contribute to increase in sensitivity)
o FLOTAC: higher sensitivity for the diagnosis of STH

Harada Mori Technique
o Materials: filter paper for fecal material and test tube
o Moisture maintained by adding boiled or distilled water
o Incubation under suitable conditions will favor hatching of ova and/or development of
larvae
o Stool samples should not be refrigerated
o Filter paper strip should be handled carefully
o Eggs in stool samples hatch and migrate towards the water

Coproculture

Baermann technique

Molecular methods (PCR, ELISA)

Both species distributed widely

Males more prone to infection (farmers)

More blood loss in females (menstruation)

Pregnant women and children at high risk

Eggs embryonate best in damp sandy soil and at a temp of 24-32 degrees Celsius

Other modes of transmission for Old World Hookworm
o Transmammary transmission (via breast milk)

Albendazole (DOC)

Mebendazole

Pyrantel Pamoate
Animal Hookworms

Ancylostoma caninum
o Common name: Dog hookworm (final host: dog)
o 3 pairs of teeth (largest mouth among hookworms)

Ancylostoma braziliense
o Common name: Cat hookworm (final host: cat)
o 2 pairs of teeth

Humans only accidental hosts

MOT: skin penetration of L3 larva
o Only penetrate underneath the skin
o Not capable of maturation in humans
o Creeping eruption (Cutaneous Larva Migrans)

Patients infected: have elevated eosinophils
Trichostrongylus

Related to hookworms

Final host: herbivores (cow, sheep)

Similar to hookworms, but have no heart lung
migration

Eggs: similar to hookworm
o Symmetrical, thin-shelled, pointed ends
o Size: larger than hookworm egg
o Trichostrongylus: larger, elongated, ends are
pointed
o Hookworms: smaller, more rounded ends
Pairs of Teeth
N. a. – 0
A. b. – 2
A. c. – 3
A. d. – 2
Size
C> D> A> B
C = caninum
D = duodenale
A = americanus
B = braziliense
57
N. Villanueva
STRONGYLOIDES STERCORALIS
Facultative: freeliving and
parasitic phase
Parasitic phase
begins when
conditions
become
unfavorable
Larva goes back
to small intestine
of humans








Possibility of
autoinfection
Life Cycle
Free-living in the environment (top portion
of the soil)

Male and female copulate

Eggs embryonate in the soil (loamy, but not
really specified what kind of soil)

L1 found in the soil
L1 becomes L3
Females only ones to become parasitic
o capable of self-fertilization (parthenogenesis)
L3 penetrates skin of humans
Heart-lung migration occurs
L3 becomes adult worm
Eggs embryonate and hatch in the small intestine
o Eggs have a Chinese lantern appearance
(similar to hook worms)
L1 in stool, then goes to soil
L1 becomes adult in the free-living phase

L1 larva in the small intestine can already
transform into the L3 larva

Trigger autoinfection

Internal multiplication happens (increased
number of worms in the small intestine)
o Lead to hyperinfection

Infections can last to many years

Strongyloides stercoralis
Common name: Thread Worm
Smallest nematode of man
STH
Facultative parasite (free-living and parasitic phase)
Habitat: small intestine
Infective stage: filariform larva
Heart-lung migration occurs
Eggs are rare in the stool sample
o Because they become larva immediately
o Stool sample contains larva = most likely Strongyloides stercoralis
o Clear thin shell (similar to hookworms)

Parasitic males have not yet been identified

Parasitic females: Parthenogenetic

Free-living females smaller than parasitic female
o Has a muscular double-bulbed
esophagus
o Intestine: straight cylindrical tube

Free-living male smaller than female
o Has a ventrally curved tail, two
copulatory spicules, a gubernaculum,
but no caudal alae

Strongyloides fulleborni
o Affects small children in Central Africa
o Can also infect monkeys, racoons, etc.
o Swollen belly sickness

Zoonotic Strongyloides
o Swimmer’s itch and swamp itch
o Ex: S. myopotami, S. procyonis
(raccons)
Mode of transmission
Larval penetration
Rhabditiform larva

short buccal capsule (has four indistinct lips)

big/prominent genital primordium








58
Filariform larva
Pathology
Diagnosis
Epidemiology
Treatment
N. Villanueva
long and slender
elongated esophagus with a pyriform posterior bulb
slightly smaller and less attenuated posteriorly compared to hookworms
posterior: forked/notched tail
o has a distinct cleft at the tip of the tail

unsheathed

female: colorless, semi-transparent, finely striated cuticle

larval invasion of skin produces erythema and pruritic elevated hemorrhagic papules

larval migration phase: causes lobar pneumonia with hemorrhage

intestinal phase
o Vietnam Diarrhea (because of war veterans)
o Cochin China Diarrhea (based on the place)
o Severe and intermittent diarrhea

Honeyform appearance of intestinal mucosa
o Eggs inside the small intestine

Hyperinfection and dissemination

Larva currens
o Allergic reaction attributed to penetrating larva

Heart-lung migration causes pneumonitis (has no specific name)

Infection can persist for many years (autoinfection)
*chronic strongyloidiasis often asymptomatic

FECT: larva

Baermann Technique (for high volume of specimen, and soil specimens, preference for
diagnosis depends on condition)

Beale’s String Test

Harada Mori

Enterotest

Less common as compared to hookworms
o Least common among STH

Target elders, AIDS patients, and immunocompromised
o Young: get infection
o Recovered, but their immune status is weak so parasite still underwent reproduction in
small intestine, lead to autoinfection (can happen many years after initial infection)

Most cases asymptomatic

Disseminated and hyperinfection more common among immunocompromised

Ivermectin with albendazole




CAPILLARIA PHILIPPINENSIS
Life Cycle

Still not sure (still has conflicting results)

Made from animal experiments
Infection from

Small intestine: larva emerge from fish
raw/undercooked fish

larva also becomes adults in the small
with the larva
intestine
o First generation: females
are always larviparous

Lays larva and larva
becomes 2nd gen
o Second generation: females
are oviparous
Diagnostic stage:

For life cycle to continue, must find its
unembryonated eggs
way to freshwater
o Will embryonate in the
freshwater after a few days
Fish ingest

Larva emerge
embryonated eggs

Humans get infected once they eat the
fish
Birds eat fish

Migratory birds get infected
59
N. Villanueva
Capillaria philippinensis

Common name: Pudoc Worm, Mystery Disease
o First reported in the Philippines
o Pudoc: barrio in Ilocos, people had a severe outbreak of diarrhea
o Discovered by Nelia Salazar (a member of the team who studied the parasite)

From superfamily Trichinelloidea

Final host: humans, other vertebrates

Natural host: migratory birds
o If no humans available to be final hosts

Intermediate hosts: freshwater or Brackish fish (Glass Fish)
o Ex: Bagsit, Ipon, Birot, Bagsang

Foodborne parasite
o Raw or undercooked fish

Habitat: small intestine

Infective stage: Larva (don’t indicate na the stage)
o Tissue or muscles of fish

Deadly if not treated
o Causes severe diarrhea
o Autoinfection, hyperinfection, and superinfection because of the larviparous female

Other species
o C. hepatica – affect the liver (hepatic capillariasis)
o C. aerophila – affect the lungs (pulmonary capillariasis)
o C. plica – urinary capillariasis
Mode of Transmission
Ingestion of undercooked fish containing larva
Adult Worms
Typical female

Has 8-10 eggs in utero arranged in a single row

oviparous
Atypical female

Has 40-45 eggs in utero arranged in 2 to 3 rows

Ovoviviparous

Larviparous in other references
Male worm

Spicule: chitinous, sheathed
Both Males and Females

Stichocytes (secretory cells in the anterior portion)

near esophagus

many stichocytes = stichosome
Eggs
Guitar-shaped (typical egg by typical female)

Also peanut shaped

Bipolar mucus plugs: flattened

Striated shell

Usually mistaken as Trichuris
o Smaller than Trichuris

Color: pale brown
Atypical egg

Already embryonated

No mucus plugs
Pathology

Pudoc Disease, Mystery Disease (thought people were cursed), intestinal capillariasis

Severe diarrhea

Abdominal pain

Borborygmus: gurgling of the stomach

Death may occur if left untreated

Protein losing enteropathy

Electrolyte loss

Autoinfection can occur
Epidemiology

Highly pathogenic (all infected persons will eventually develop the disease)

Endemic areas: Ilocos region, La Union, Pangasinan, Zambales, Cagayan, Isabela,
Compostella Valley, Zamboanga del Norte
o Also in Mindanao (because of migratory birds)
Treatment

DOC: Mebendazole

Albendazole

Electrolyte replacement and high protein diet
60
N. Villanueva
ANISAKIASIS
*Anisakiasis: name of the disease
Parasite lives in stomach of
marine mammals/dolphins
(adult worms are embedded
in the gastric wall)
Eggs hatch
Cyclops can eat the L3 larva
Man eat
fish/squid/crustaceans
Life Cycle

Eggs found in the stool of
dolphins

Eggs embryonate in water (L2
larva)

When it comes out, becomes L3
larva (infective stage to final
host and paratenic host)

Then get eaten by the paratenic
hosts

L3 more concentrated in the fish
viscera, but can also be found
in their muscles

Dolphins eat the fish

Dolphins can also eat the
Cyclops immediately

Larva in the small intestine
Anisakiasis
Anisakis simplex and Pseudoterranova decipiens
Other related species: Contracaecum sp., Hysterothylacium sp.
Common name: Cod Worm, Herring Worm
Not yet documented in the Philippines
Nematode parasites of whales, dolphins, porpoises, walruses, seals, sea lions, and other deep-marine mammals
Have elongated vermiform bodies without segmentation
Final host: marine mammals (dolphins, whales)
Paratenic host: fish (small) and squid
o Harbor larva, no development

Accidental host: humans (L3 do not develop into adults)

Intermediate host: Microcrustaceans (Cyclops)

Infective stage (to humans): L3 larva (to both humans and animals)
Mode of transmission
Ingestion of undercooked or raw seafood containing larva (saltwater fish, squid, rare in Crustaceans)
L3 Larva
Anisakis simplex

Milky white color, 19-36 mm in length

Has a long stomach

Has a blunt tail with a mucron (attachment organelle)

This is called the Type I larvae

Other species of Anisakis: L3 have shorter stomachs and blunt tails, are called Type II larvae
Pseudoterranova decipiens

Yellowish brown in color, 25-50 mm in length
Pathology
Anisakiasis or Anisakidosis

Aka Herring’s Disease, Gastrointestinal Anisakiasis

Occurs within 1-12 hours after ingestion

Abdominal pain, nausea, vomiting diarrhea

Irritation of small intestines

Eosinophilic granulomatous reaction
o larva invade the submucosa of the small intestine
o this results in hemorrhage and inflammation
o larvae may die and detach
o if penetration is deep, causes an eosinophilic granulomatous/allergic reaction

urticaria (hives), asthma, conjunctivitis, contact dermatitis are observed among workers in fish
and marine product processing factories

Perforation of intestines reported (in heavy infections)

You can cough out the parasites (regurgitated)

Symptoms can be mistaken for peptic ulcer disease, cholecystitis, or even gastroenteritis

Gastric form mimics appendicitis, Crohn’s disease, intestinal obstruction, or diverticulitis

Ectopic anisakidosis: larvae found invading the oropharynx, esophagus, and colon
o Tingling throat syndrome: when oropharynx is involved
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61
Epidemiology
Diagnosis
Treatment
N. Villanueva
Common in Japan and Netherlands
Also common in Korea, France, Germany, Italy, Spain, UK, North and South America, Egypt
Common among coastal populations (because of fish)
Ingestion of sushi or sashimi or pickled herring
Gastroscopic Examination (Endoscopy, Gastroscopy)
Biopsy
Worms may be coughed off by patients
Serology: ELISA, Radioallergosorbent Test (RAST)
Albendazole
Surgery or removal of larval stages

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TISSUE NEMATODES
ANIMAL ASCARIDS
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Toxocara cati (cats) and Toxocara canis (dogs)
These parasites are roundworms belonging to Family Toxocaridae and Order Ascaridida
Limited development in humans (only accidental hosts)
Mode of transmission: ingestion of embryonated eggs (soil transmitted zoonosis)
Eggs release larva, larva does not develop (only found in the different organs, try to undergo heart-lung migration, but will not
develop into adults)
Vertical transmission in animals
o Toxocara cati: more through lactation
o Toxocara canis: more through transplacental route
Toxocara cati causes less infections (due to lesser defecation patterns of cats)
Disease: Visceral Larva Migrans (VLM)
o Symptoms: Wheezing, LRT symptoms (bronchospasms), can progress to pneumonia and respiratory failure
o Associated with liver enlargement and necrosis
Usually affects children
Associated disease: ocular larva migrans (OLM, larva in eyes), covert toxocariasis (hidden)
o VLM and OLM can coexist
Other diseases: Neurological toxocariasis (can cause encephalitis)
Diagnosis: Detection of larva (biopsy), surgery, ELISA (Detection of IgG) using Toxocara excretory antigens, molecular
methods, NOT DFS (because dealing with larva), Western Blot, Medical imaging
Treatment: Albendazole, mebendazole (together with anti-inflammatory medications)
PARASTRONGYLUS CANTONENSIS
Rat ingested snail with the
L3 larva (can also ingest the
vegetables/leaves where the
snail passes through, with
the slime of the snail)
Humans eat snails
Life Cycle

L3 mature in the lungs of rats

Eggs in stool


Larva will not become adults
Larva goes to the brain
62
N. Villanueva
Parastrongylus cantonensis

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
Aka Angiostrongylus cantonensis
Formerly Haemostrongylus ratti
Common name: Rat Lung Worm
Definitive host: Rats (Rattus rattus)
Humans are accidental or incidental hosts only
Intermediate hosts
o Achatina fulica (giant African snail)
o Hemiplecta sagittifera
o Helicostyla macrostoma
o Vaginilus plebeius
o Veronicella altae

Paratenic hosts: prawn, crab, vegetation

Cantonensis: in Canton, China

Infective stage: L3 Larva

Habitat: lungs of definitive host (two main branches of pulmonary arteries)

Eggs contain L1 larva (eggs have delicate hyaline shells)
Mode of Transmission

Ingestion of raw or undercooked infected snails

Ingestion of paratenic hosts

Drinking contaminated water

Eating salad where the snail was
Larva

L1: distinct small knob near tip of the tail

L3: have two well-developed chitinous rods below its buccal cavity (rods have expanded knoblike tips)
Adult Worms
Female

Barber pole appearance
o Dark: intestine
o White: uterus
Male – has the spicule
*both have well-developed caudal bursa (kidney-shaped and single lobed)
Disease Manifestation
Angiostrongyliasis/Parastrongyliasis

Eosinophilic meningoencephalitis
o Headache, vomiting, neck stiffness, seizures, eosinophilia, neurologic abnormalities
o Inflammation of brain meninges
o Headache: intermittent occipital or bitemporal headache
o Can cause diplopia (blurring vision)
o Increased eosinophils

Incubation period: 6-14 days (or 12-47 days)

Ocular involvement reported (intraocular hemorrhage and retinal detachment)

Prognosis is good (usually self-limiting)

Postmortem examination may show leptomeningitis, encephalomalacia, moderate ventricular
dilation

Dead worms can result in inflammatory reaction and local tissue necrosis
Diagnosis

Difficult

Travel history and exposure must be noted

CSF examination: more than 10% of WBCs is composed of eosinophils
o CSF Protein: mild elevation

Charcot-Leyden crystals may be seen in the meninges

CT-Scan

Serology

PCR
Epidemiology

Described among rats in Canton, China in 1935

Human infection reported in Taiwan in 1945

Endemic Areas: Southeast Asia, Pacific Basin

Ocular Angiostrongylus has been reported
Treatment

No recommended treatment

Mebendazole

Thiabendazole

Albendazole can be given
63
N. Villanueva
TRICHINELLA SPIRALIS
Life Cycle
MOT for Pigs:

Domestic life cycle
o Pig eat scrap food with larva
o Pig eats another pig (carnivorism)
o Pig eats rat
o Rat can also transmit it to other rats

Sylvatic life cycle
o Omnivore and carnivore
o fraction of the pathogen population's
lifespan spent cycling between wild
animals and vectors
People can get the parasite upon accidental
ingestion of pork with larva or when they are
hunting (also through improper preparation of
pork, like microwaving)
Pigs develop the parasite



Larva penetrates mucosa of the small intestine


Larva goes to
stomach then to the
small intestine
Adults in the small
intestine
Reproduce then
produce larva
Goes to the striated
muscle
Cyst: produced by
nurse cells of the
parasite
Trichinella spiralis
Common name: Trichina Worm, Muscle Worm, Garbage/Trash Worm
Nematode found in the tissues
Final host: pigs and other mammals
Man only an accidental host
Habitat: small intestine, striated muscle
Infective stage: encysted larva (life span of 5-10, or up to 40 years)
Larval stages usually found in gastrocnemius, deltoid
Other distinct species
o T. nativa: occurs in arctic and subarctic zones

high pathogenicity

high resistance to freezing
o T. nelsoni: occurs in tropical Africa
o T. britovi: occurs in temperate Paleoarctic region, very low
pathogenicity, 2nd most common
o T. pseudospiralis: cosmopolitan, does not encyst, infectious to birds
o Others: T. murrelli and T. papuae

Host serves as both the final and intermediate host (harbors both adult and larval stages)

Larva: has a spear-like, burrowing anterior tip (what it uses to burrow into the sub-epithelium of the villi, where they undergo
four molts)
*still has larval stages, just not shown
Mode of Transmission
Ingestion of undercooked or raw pork (other meat) infected with larva
Adult worms
Male

Has conical papillae (for copulation, located in the posterior)
o For holding the female during copulation

Has a single testis
Female

Has the larva inside

Has a single ovary

larviparous
Disease Manifestation
Trichinosis or Trichinellosis
and Pathology

Intestinal/Enteric phase: minor, usually non-specific gastroenteritis

Muscle invasion (Invasive Phase)
o Pathology associated to the larva
o Fever and eosinophilia
o Induces greatest increase in eosinophils
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64
N. Villanueva
High levels of IgE
Muscle pain
Myocarditis (most severe symptom): can cause pericardial pain, tachycardia, and
ECG abnormalities
o Some may experience CNS involvement

Psychosis, meningoencephalitis
Convalescent phase: fever, weakness, pain, and other symptoms start to abate
Usually good prognosis (full recovery expected)
Biopsy of Muscle (gold standard, or definitive test)
o Shows presence of larva
o Can use deltoid, gastrocnemius, pectoral, gluteus
Biochemical tests
CBC: show increased eosinophils
Blood Chemistry: shows increase creatine kinase and lactate dehydrogenase
Very high levels of eosinophils
ELISA (detection of antibodies)
Bentonite Flocculation Test
o Serologic test using the serum sample
o Detect antibodies against Trichinella
o Reagent: Trichinella antigen attached to Bentonite (carrier particle)
o Positive result: flocculation (reaction that is in between agglutination and
precipitation)
o Bentonite: clay
Bachman Intradermal Test: use of 1:10,000 dilution of larval antigen
o Patient injected with Trichinella antigen in the skin
o Positive result: wheal and flare reaction

Indicates previous exposure to the parasite
o Also a type of xenodiagnosis
Beck’s Xenodiagnosis
o Uses albino rats
o Rat eats muscle, kill the rat after around 14 days
o Then you can find the female worm in the small intestine
Life cycle maintained in the environment by carnivores
reservoir hosts: boars and bears
Humans usually infected by ingestion of raw or undercooked pork
Mebendazole (Intestinal Phase)
Steroids and Mebendazole (for severe acute infections, muscles)
Health education
Thoroughly cook meat (77 degrees Celsius)
Freeze meat (-15C for 20 days or -30C for 6 days)
Cannot be prevented via handwashing
o
o
o
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Diagnosis
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Epidemiology
Treatment
Prevention
DRACUNCULUS MEDINENSIS
Humans ingest
water contaminated
with the copepods
or L3
Larva goes to the
subcutaneous
tissue
After 1 year of
maturation, female
is ready to release
the larva
Life Cycle

Copepods goes to stomach

L3 larva penetrates the
stomach

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
Develop into adults
Diagnostic: find only 1 or 2
pairs of male and female
worms
Migrates to the surface of the
skin
Forms a blister (where female
emerges to release the L1)
Release of larva triggered if
person immerses feet in the
water
65
N. Villanueva
Dracunculus medinensis

Common name: Guinea Worm, Fiery Serpent, Medina Worm, Dragon Worm

Largest nematode infecting man (female around 1 meter in length)

Parasite of antiquity (old parasite)

Final host: humans

Intermediate host: Copepods (Cyclops) found in freshwater

Infective stage to FH: L3

Infective stage to IH: L1

Habitat: subcutaneous tissue

Primarily found in Africa
Mode of Transmission
Ingestion/Drinking of contaminated water with the copepods or L3
Disease Manifestation
Guinea Worm Disease; Dracunculiasis

Formation of blister

Urticaria

Vomiting

Diarrhea

Asthma attacks

Symptoms disappear once ulcers appear

Discharge of the worm
Epidemiology

Water sources can be breeding grounds for copepods
o Ex: stepwells of India, open ponds, Open Cisterns

Important parasite in middle east, Central India Pakistan, Africa
o Can also be found in Asian countries

Disease is nearing its eradication
Diagnosis

Appearance of cutaneous lesion and worms

X-ray: visualization of calcified worms
Treatment

Removal of worms using a stick
o Don’t break the worm

will trigger an allergic reaction

can also cause calcification of the parasite

will need surgery to get the worm out

can immerse foot in water to make the larva go out

DOC: Metronidazole
FILARIAL WORMS


Nematodes found in blood and lymphatics, transmitted by vectors
Wuchereria bancrofti (more prevalent) and Brugia malayi
Mosquitoes suck human blood

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Life Cycle
Drops of blood drop on skin
Blood contains the larva (penetrates the skin through the bite wound)
Larva is not injected
66
N. Villanueva
L3 larva goes to lymphatic system
Microfilaria released to bloodstream
Mosquito bites human
Unsheathed microfilaria migrates to the
thorax of the mosquito
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Develops into adult male and female
Reproduce to produce microfilaria
Passes through the lungs (blood vessels of lungs)
Goes to the peripheral blood
Diagnostic stage
Ingests microfilaria
Microfilaria goes to mosquito’s stomach
Sheath sheds
Microfilaria becomes L1 then L3
L3 migrates to proboscis
Filarial Worms
Malayan Filariasis: seen in Palawan, Eastern Samar, Agusan del Sur, Sulu
Disease seen more in adults than children
Males more affected
Final host: man
Intermediate host: mosquito
W. bancrofti: prefer localization in scrotal lymphatics
B. malayi: less severe
Infective stage to FH: L3 filiform larva (not filariform, describes the
appearance)

Infective stage to IH: microfilaria (sheathed)

Diagnostic stage: microfilaria

ideal breeding sites for mosquitoes:

Colocasia esculenta

Musa textilis
o Water lilies

Those constantly exposed: have less severe symptoms
o Immune system is primed/exposed
o People not exposed: when they go from a non-endemic to an endemic area, they may experience more severe
symptoms (called the Expatriate Syndrome)
Wuchereria bancrofti
Brugia malayi
Common name
Bancroft’s Filarial Worm
Malayan Filarial Worm
Intermediate host
Mosquitoes

Mansonia bonneae (freshwater)

Aedes poecilus (transmit in urban areas)

Mansonia uniformis (rice paddies)

Anopheles flavirostris

Anopheles

Culex (primarily transmit in agricultural
areas)
Life Span
10 years
Movement
Graceful, smooth movement
Kinky (angular) movement
Adult Worms

Sheathed

Sheathed

Non-overlapping/organized body nuclei

Overlapping/non-organized body nuclei

Unstained with Giemsa

Stains pink with Giemsa

No posterior/terminal nuclei

Contains posterior/terminal nuclei

Shorter than Wuchereria
Periodicity
Nocturnal
Subperiodic (12pm-8pm)
*microfilaria released during the day
Cephalic Space
Length = breadth (width)
Length = 2 x breadth
Habitat
Lymphatics (in adults)
Mode of Transmission
Active larval penetration
Disease Manifestation
Lymphatic Filariasis

To get the infection, they are constantly bitten by the mosquito

Asymptomatic Phase: thousands to millions of microfilaria in the blood and adult worms in the
lymphatics
o Seen in “Endemic Normals” (they have in their blood the parasite antigen instead of
the microfilariae)
o Patients appear healthy and no clinical manifestations seen
o Microfilaria come from lymphatic vessels (from the adult worms there)
o Symptoms are nonspecific

Early Manifestation: Fever, lymphadenitis, welling, redness of arms and legs, vomiting,
headache
o Lymphadenitis: inflammation of lymphatic vessels, triggered by the adult worms
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67
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Diagnosis
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N. Villanueva
o Main pathology attributed to adult worms
ADLA (Acute Dermatolymphangioadenitis)
o Inflammation of lymph
o Adenolymphangitis
o Swelling or inflammation of lymphatic vessels
o Most common manifestation
o This is of bacterial etiology (most frequently associated with Group A Streptococcus)
Constant irritation and inflammation triggers chronic phase after many years
Chronic Phase: Elephantiasis, Hydrocoele, Chylocoele, Lymphocoele, Chyluria
o 10 years or more after the initial infection
o Elephantiasis: enlargement of different parts of the body
o Parasites might be dead already (life span of around 10 years)

Parasites calcify and cause obstruction and inflammation (this triggers the
Elephantiasis, Hydrocele, Chylocele, Chyluria)

Accumulation of lymphatic fluid

Chyluria: fluid find its way to the urinary system (discharge of urine
is milky)
Wolbachia: also attributed to the pathology, type of bacteria
o Gram-negative, type of Rickettsia
o Found in the insect vector and inside the filarial worms
o If worms die, this will also be excreted and also triggers inflammation
o Promotes inflammation in Filariasis
Tropical Pulmonary Eosinophilia – attributed to microfilaria
o Microfilaria in tissues (passes through the lungs and tissue)
o Paroxysmal nocturnal cough

Respiratory symptoms, lung function impaired

Coughing during the night coinciding with release of microfilaria
o Hypereosinophilia
o Type of Occult filariasis (hidden filariasis, because none in blood)
Wuchereria: more severe deformity
o Enlargement happens below the waist
o Thighs, males: scrotum
2nd leading causes of permanent disability
o Enlargement is irreversible
Brugia: can selectively induce CD4+ lymphocyte apoptosis (can contrinute to immune
unresponsiveness to filariasis)
Best to diagnose early (when acute and asymptomatic)
Thick smears (Giemsa) – look for microfilaria
o W. bancrofti: collect blood from 10 pm to 2 am (Nocturnal Periodicity)
o B. malayi: subperiodic periodicity
Diethylcarbamazine Provocative Test
o Orally
o Done especially if difficult to collect sample during the night
o 3 mg/weight kilogram of patient
o Triggers release of microfilaria
o With this, do not need to wait for night for microfilaria
Concentration Techniques
o Knott’s Concentration Technique

9 ml of 2% formalin added to 1 ml of whole blood

Formalin added to lyse RBCs (better visualize microfilaria)

Centrifuge

Positive result: sediment

Sediment stained with Giemsa
o Membrane Filtration Method (Nucleopore filter)

Pore size is smaller than the microfilaria

RBCs pass through the filter

Residue on filter paper = microfilaria
Serology
o Detection of circulating filarial antigen (CFA)
o Rapid diagnostic test

Brugia Rapid (using Ag BmR1, for Brugia)

Using WbSXP-1 (for Wuchereria)
Use of urine samples
Molecular methods
68
Epidemiology
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Treatment
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Prevention
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N. Villanueva
Ultrasonography (useful for elephantiasis)
Bancroftian Filariasis: more widespread, affects India, SEA, Pacific Islands, Africa, and South
and Central America
Malayan Filariasis – affects SEA
Common in Bicol (because of abaca, where the mosquitoes breed)
o Most affected: farmers working in abaca plantations
Disease among adults (elephantiasis)
o Because they got the infection when they were children, manifested when they were
adults already
DOC: Diethylcarbamazine (DEC)
Ivermectin
Albendazole
doxycycline
For elephantiasis, doctor aspirates fluid
o Can lead to bacterial infections
Insect repellants
Vector control
Mass drug administration (MDA)
Brugia timori

Similar to bancroftian filarisis in clinical presentation

Microfilaria
o Longer than B. malayi
o Cephalic space = 3:1
o Sheath unstained by Giemsa
o Periodicity: nocturnal
o Vector: Anopheles barbirostris
OTHER FILARIAL WORMS


IS still L3 larva, diagnostic stage still microfilaria
Only sheathed: Wuchereria, Loa loa, Brugia (others: unsheathed)
69
N. Villanueva
LOA LOA
Loa loa

common name: African Eye Worm
Vector

Chrysops, Mango fly, Tabanid fly
Disease Manifestation
Loaiasis

worms able to migrate through tissues and even through conjunctival tissue across the
eyeball
o Edema of Conjunctivitis and eyelids
o Calabar swellings: localized subcutaneous edema (also called fugitive
swelling)

Allergic reaction indicative of Loa loa

Cause blindness

Progressive keratitis
Diagnosis

Presence of calabar swellings (allergic reaction)

Appearance of worm in conjunctiva

Detection of microfilaria

Skin test
Periodicity
Diurnal (during the day)
Epidemiology
Sudan, Congo, West Africa
MANSONELLA OZZARDI


common name: New World Filaria
Disease manifestation: Mansonellosis ozzardi
o Usually asymptomatic
o Inguinal adenopathy: inflamed lymph nodes
in the inguinal area
MANSONELLA STREPTOCERCA




Formerly known as Dipetalonema streptocerca
Vector: small midges belonging to Culicoides
Disease manifestation: pruritus dermatitis with
hypopigmented macules (pale spots) and inguinal
adenopathy
Microfilaria found in the skin
o Unsheathed: nuclei extend up to the tip, tip
bent in the form of a shepherd’s crook
MANSONELLA PERSTANS
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Formerly Dipetalonema perstans
Common name: persistent filarial worm
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Disease manifestation: usually benign, calabar
swellings, pruritus, hives, fever
Causes Kampala or Ugandan Eye Worm
ONCHOCERCA VOLVULUS
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Onchocerciasis: major cause of blindness in some
parts of Africa
Also known as river blindness (blindness)
Vector: Black fly (Simulium damnosum)
Can cause skin nodules, progressive keratitis
Diagnosis: history, symptoms, microfilaria in nodules
DIROFILARIA IMMITIS
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Common name: Dog heartworm
Final host: dogs
Accidental host: man
Vector: mosquitoes
Pathology: presence of peripheral nodules in the lung
(coin lesions), obstruction of heart
70
N. Villanueva
TREMATODES
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belong to Phylum Platyhelminthes
o Class Trematoda
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Order Digenea
o Class Cestoda (next topic)
Also called flukes
Trematodes: “body with holes”
o Possess muscular suckers
Has at least 1 intermediate host
o Mollusk
o Can have 1 or 2
o All 2, Schistosoma has 1 intermediate host only
GENERALITIES
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All appear flat and leaf-like
o Except Schistosoma species (cylindrical)
All are bilaterally symmetrical and unsegmented
Tegument (body covering) is non-cellular
o Form syncytium (fused structure)
All monoecious except Schistosoma species
o Also called hermaphrodites
o Both testes and ovary in one parasite
o Schistosoma: dioecious
Possess incomplete alimentary canal
o Digestive system
o No anus (excrete is diffused)
o Mouth with suckers, pharynx
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Bifurcate, fork
o Schistosoma: has no pharynx and its intestinal ceca
connect
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Other trematodes: putol or “blind”
Possess spines and tuberculations
o Protruding structures
o Depends on species
All possess two suckers except Heterophyes heterophyes
o Parasites with two suckers belong to Genus
Distoma/Distomata (distomata: plural)
o Oral sucker: for nutrition
o Ventral sucker: also known as acetabulum, for
attachment, not connected to other parts of the
parasite
o Heterophyes: has 3 suckers
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Genital sucker, gonotyl (used during
reproduction, connect testes and ovary)
Reproductive organs are well developed
o Ovaries and testes, usual is 1 ovary and 2 testes
o Schistosoma: >2 testes
Absent body cavity (pseudocoel)
No circulatory, skeletal, and respiratory systems
Nervous system – basic/rudimentary
o System composed of Ganglion cells (usually a pair,
found anteriorly)
Bilaterally symmetrical excretory system with collecting
tubules and capillaries that terminate in flame cells
(solenocytes)
o Basically their excretory system consists of flame
cells or solenocytes (they function like kidneys)
Eggs – diagnostic stage
o Operculated: has an operculum
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Lid-like structure
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Open to allow larva to exit the egg
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Except Schistosoma (non-operculated)
o Schistosoma: already embryonated once released
Intermediate hosts (all except Schistosoma)
o First: mollusk (snails)
o Second: wide variety of plants, insects, animals, water
plants, fish, crustaceans
MOT: ingestion
o Except Schistosoma (skin penetration)
IS: metacercaria (larval stages)
o Except Schistosoma (fork-tailed cercaria)
Uterus: can have eggs inside
Vitellaria: branching structures on lateral portion for eggshell production
GENERAL LIFE CYCLE
General Life Cycle of Trematodes
 From the 2nd intermediate host
 Metacercaria becomes adults in the
habitat (habitat depends on species)
Adults reproduce  Produce eggs
 Eggs in stool: immature
Eggs must go to  To embryonate/mature
freshwater
 Embryonated: has larva inside
 Would then hatch, emerge through the
operculum
 1st larval stage that emerges:
miracidium
o Motile larval stage
o Locomotory structure: cilia
*In other life
 Embryonated eggs can be ingested by
cycles
the intermediate host directly
 Hatch inside the intermediate host
Miracidium goes  Becomes sporocyst
to the 1st
o The “mother sporocyst”, from this
intermediate host
daughter sporocysts emerge
o Daughter sporocyst becomes the
redia
 Redia becomes cercaria
Cercaria goes to  Cercaria develops and encysts
the 2nd
 After encystation, becomes the
intermediate host
metacercaria (what infects the
human)
MOT: ingestion
of metacercaria
71
N. Villanueva
BLOOD FLUKES
SCHISTOSOMA SPP.
Life Cycle of Schistosoma spp.
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No metacercaria
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Cercaria cannot survive in chlorine (only in freshwater, unchlorinated water, water with no salt)
MOT: skin penetration
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IS: fork-tailed cercaria
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When feet is immersed in freshwater
o Only in freshwater and usually happens in the morning
o Cercaria has lytic enzymes used to break down skin
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Only head of cercaria enters
o Once inside the skin, tail part falls off
o Cercaria without tail is called schistosomule
Schistosomule goes to blood
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Migrates to lungs
vessels (superficial lymphatic
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From lungs, goes back to blood vessels again (portal veins)
vessels or subcutaneous veins)
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Becomes adult worm in the blood vessels
Adult worms reproduce
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Produce eggs
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Eggs deposited in the blood vessels (mucosal or submucosal terminal veins or
capillaries)
o May go to the liver, intestinal tract, and urinary bladder
o Egg deposition usually begins from 24 th to 27th day after cercarial penetration

Eggs will be found in the stool or urine (depends on the species)
o Can be found in the blood (but invasive to get blood, so usually stool or urine is
used)

When released, eggs already embryonated (takes 10 days to embryonate)
o Larva inside: miracidium
o Miracidium: have an apical papilla, epidermal plates covered with cilia,
primitive gut, pair of cephalic unicellular penetration glands opening by a duct at
the base of the apical papilla, two pairs of flame cells, germinal cells
Egg goes to freshwater

Embryonated egg hatches (within 2-4 hours)
o No operculum, just cracks/hatches longitudinally

Free-swimming miracidium emerges (can survive overnight)
o Miracidium are phototactic and swim actively in surface water
o Remain infective for snails for 8-12 hours, infectivity diminishes with time
o Said that secretions/excretions of O. h. quadrasi attract miracidia, but the
chemotactic molecules have not yet been identified

Eggs hatch only in clean fresh water with sufficient oxygen
o Will not hatch in salinity greater than 0.7% or at mammalian body temperatures
o Ideal: temperature of 25-31 degrees Celsius in slightly alkaline water
Miracidium goes to 1st

Miracidium penetrates the snail
intermediate host (snail)
o Contact with soft parts of snail
o Penetration is effected by movement and lytic action of cephalic gland
secretions
72
N. Villanueva
Factors that influence infection of snails: age of snails and miracidium, number
of miracidium per snail, length of contact time, water flow, turbulence
o Ciliated surface disappears once penetration is complete
Miracidium becomes sporocyst (no redia stage)
o Miracidium develops into mother sporocysts after a few days
o After 96 hours after penetration, becomes an elongated sac filled with germinal
cells
o On 8th day, germ cells bud off epithelial lining and develop into daughter
sporocysts
o Daughter sporocysts migrate to liver through the loose connective tissue
Sporocyst reproduce asexually and become free swimming cercaria (after 60 to 70
days)
o Limiting factor of number of cercaria produced: size of snail host (S. mansoni
and S. haematobium have bigger snail hosts, have more cercaria, Biomphalaria
biggest intermediate host)
o Singly infected snails: shed 230 cercariae
o Snails with multiple infections: shed 280 cercariae
o Cercaria release usually during night
Cercaria released from 1st intermediate host
Chemotaxis: swims toward light (detects antigens from human host)
Penetration stimulated by skin lipids
Dimethylate and niclosamide repel cercaria when applied to skin, but impractical due to
need to frequent reapplication
o
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Cercaria swims to patient
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Schistosoma spp.
Male: shorter and thick
No pharynx
Female: longer and thin/slender
Contains the uterus and ovaries
Found in copula (in copulation)
Entrenched together (most romantic)
Female inside the gynecophoric canal on the male
Final host: man
o But has a wide range of definitive hosts (domestic mammals such as dogs, pigs, cats, carabaos, and cows
o Susceptibility to infection can vary (some may be permissive and become infected over an extended period of time
and some may be non-permissive wherein schistosomes are stunted or mature but die prematurely)
Intermediate host: snails
Infective stage: fork-tailed cercaria
Habitat: mesenteric veins, blood
MOT: skin penetration
japonicum: found in the Philippines, Japan, China, and other Asian countries
mansoni and intercalatum: Africa
haematobium: Africa and Middle East
mekongki: Mekong river basin in Cambodia, Myanmar, Asia
injection of irradiated cercariae of Chinese strain confers resistance against
homologous strain (but not against Philippine strain)
mouse pathogenicity of Chinese strain is less than Philippine strain
most studies of biology of S. japonicum have been done on the Leyte strain
eggs in multicellular stage when released
o immature eggs passed in feces no longer mature in soil and are not viable
o mature eggs in feces can survive and still hatch up to a week if desiccation is slow
male: testes arranged in one row above ventral sucker
female: single pyramidal ovary located in midline
worms ingest red blood cells and possess a protease (hemoglobinase) that breaks down globulin and hemoglobin
o also utilize glucose at a rapid rate
o absorb nutrients through the body wall
main pathology due to the egg
73
Common name
Habitat
Intermediate Host
Adult stages
Location of ovary
Egg Production
Integumentary
Tuberculations
Number of Testes
Eggs
Reservoir Host
Disease Distribution
Disease (S.
japonicum)
N. Villanueva
S. haematobium
Vesical Blood Fluke
Vesical, Prostatic, Uterine
Plexuses of the Venous
Circulation
Bulinus
S. japonicum
Oriental Blood Fluke
Superior mesenteric vein of small
intestine
S. mansoni
Manson’s Blood Fluke
Inferior mesenteric vein of the
colon
Oncomelania hupensis quadrasi
Largest
Middle
Greatest (3000 eggs per worm pair
per day)
None
Biomphalaria
Smallest
Anterior ½
190-300 eggs/day
Prominent/Grossly tuberculated
Fine
6-8
Oval with recurved hook or knob,
smallest
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ovoid, round, pear-shaped
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pale yellow
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thin-shelled (with residual
tissue or red cells adherent
to it)
Humans and other mammals (dogs,
pigs, cats, carabaos, rodents,
monkeys)
China, Indonesia, Japan, PH
8-9 (arranged in a zigzag pattern)
Elliptical with lateral spine
4-5
Elliptical with terminal spine
Humans, non-human primates
Humans
Posterior ½
30 eggs/day
Africa, Madagascar, West Indies,
Africa, Middle East, India,
Suriname, Brazil, Venezuela
Portugal
Oriental Schistosomiasis, Snail Fever, Schistosomiasis japonica

Initial phase
o When cercaria penetrates the skin
o Schistosome Cercarial Dermatitis
o Trigger allergic reaction and inflammation, redness where parasite enters
o Petechial hemorrhages
o Localized edema and pruritus/itchiness
o Schistosomule goes to blood vessels

Pulmonary Schistosomiasis – for migrating larval stages, transient period
o Migrates to lungs, causes respiratory manifestations
o Cor pulmonale: dyspnea, cough hemoptysis
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Cor pulmonale: abnormal enlargement of right side of heart because of disease
of the lungs or pulmonary blood vessels
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Parasite can migrate to heart
o Adult worms, when migrating, can pass through the liver

Acute phase: Katayama Syndrome/Fever
o Happens 1-3 months after initial phase
o Parasite in the mesenteric veins
o Abrupt onset of fever, chills, muscle pain, headache, hepatomegaly, lymphadenopathy,
dysentery
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Dysentery: bloody diarrhea, due to the eggs, eggs pass through blood vessel
linings and go to the intestines
o Fulminating meningoencephalitis with fever, confusion, lethargy, coma
o Acute and intestinal phases are usually overlapping

Intestinal phase: mucosal inflammation, hyperplasia, ulceration microabscess, blood loss, lower
abdominal pain
o Colonic involvement: during early period of egg deposition, ulcerations cause dysentery or
diarrhea
o Eggs are released to the liver (because blood vessels supplies the liver)
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Chronic infection: Hepatosplenic Schistosomiasis
o Eggs become trapped up by the portal blood flow (abundant eggs in the liver)
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Trigger inflammation reaction because eggs are antigenic (triggers immune
system)
o Accumulation of eggs in the portal triads
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Eggs cause obstruction
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Form granulomas: masses/aggregates of activated macrophages and immune
cells
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Causes portal hypertension and hepatosplenomegaly
o granulomatous inflammation
74
N. Villanueva
granulomas eventually cause fibrosis – Symmer’s Pipe Stem Fibrosis (also called
Fibro-obstructive Hepatic Schistosomiasis)
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hallmark/pathognomonic for Schistosomiasis
o Leading to Esophageal Varices: varicose veins in esophagus, can explode and lead to
death
o Leading to Massive Ascites: accumulation of ascitic fluid (stomach enlarges)
o Tumors and increased intracranial pressure
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Aberrant migration may obstruct circulation of brain and spinal cord (can cause seizures,
paresthesias, transient ischemic attacks, and strokes)
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Cerebral Schistosomiasis (motor or sensory disturbances)
o Highly associated with S. japonicum, high propensity, lower risk in other species
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Primary lesion is a granulomatous hypersensitivity reaction around a single egg or egg cluster
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Link to occurrence to colon cancer and liver cancer
o Prolonged inflammation = can cause cancer
Intestinal Bilharziasis
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Cercarial Dermatitis
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Acute Schistosomiasis = Katayama like fever
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Association with kidneys
o Hepatosplenic Schistosomiasis (similar to S. japonicum)
o Nephrotic syndrome (affects glomerulus, due to circulating immune complex that
triggered inflammation in the kidneys)
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Spinal cord schistosomiasis
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Manifestations almost the same with S. japonicum but less severe
Urinary Bilharziasis, Egyptian Hematuria
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Egyptian – mostly seen in the Middle East
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Light infections usually asymptomatic
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Symptoms found in heavy infections
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Early signs and symptoms: dysuria and hematuria
o Not much diarrhea, because parasite found in blood vessels supplying the bladder,
symptoms are more on the urinary side
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Vesical mucosa: yellow sandy patches
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Granuloma formation leading to fibrosis and ulceration, pseudoabscess in the bladder
o Granulomas can be seen in the bladder
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Pulmonary involvement common (also has Cor pulmonale)
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Link with bladder carcinoma (squamous cell carcinoma)
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Stool Exam: Kato-Katz, DFS, FECT, MIFC
o For S. japonicum and S. mansoni
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Modified Acid-Fast Staining
o Stain the egg-shell (structure with the acid-fast property)
o Positive: S. japonicum, S. mansoni, and S. intercalatum
o Positive result: red color
o Modified Ziehl-Neelsen
o Negative: S. haematobium
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Detection of eggs in urine for S. haematobium
o Best to collect urine from 12 pm to 3 pm (time when there is highest recovery)
o Concentration techniques: Nucleopore Filtration Technique
o Centrifuge urine, analyze the sediment

Faust-Meleney’s Egg Hatching Technique
o Determine the viability of the egg
o Positive result: egg hatches, releasing the miracidium
o Use a specialized flask, cover with dark paper, put egg and distilled water in the flask
o Put a flashlight at the opening of the flask, miracidium swims towards the light
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Rectal snips and imprints (most sensitive and most invasive)
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Rectal or Liver Biopsy
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Immunodiagnosis/Serologic tests
o Intradermal tests using adult worm extracts
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Fairley’s Test
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Positive result: wheal and flare reaction
o Indirect hemagglutination
o ELISA
o Detection of antigens (CCA and CAA, SEA)

CCA: circulating cathodic antigen
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CAA: circulating anodic antigen
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SEA: soluble egg antigen
o
Disease (S. mansoni)
Disease (S.
haematobium)
Diagnosis
75
N. Villanueva
COPT (Circumoval Precipitin Test)
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Confirmatory test/Definitive test in the Philippines
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Positive result: bleb or septate precipitates
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Sample: serum
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Find antibodies against Schistosoma
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Reagent: Lyophilized schistosome egg (serves as antigen)
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Step 1: Place few amounts of lyophilized egg on glass slide
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Step 2: Place serum sample
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Step 3: Mix using applicator sick
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Step 5: On four corners of the size of a cover slip, place crushed/ground glass
or a drop of nail polish
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Step 6: Place the cover slip on top of the glass/nail polish (tuntungan, so the egg
won’t break)
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Step 7: Use melted paraffin to seal the edges of the cover slip
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Incubate at 37 degrees Celsius for 24-48 hours
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Antibody will react with the antigen, form a bleb (structure that grew on the egg)

Molecular Methods
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Use a rabbit
o Historical notes from Sir Flores! 😊 (They did this daw dati)
o Use infected snails
o Put crushed snails on shaved underbelly of rabbit
o Kill rabbit after a few months, drain all the blood
o Get the lyophilized egg
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28 endemic provinces in the Philippines
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Covering 190 endemic municipalities
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National Prevalence Rate = 2.5% (DOH, 2008)

Mindanao: 60%, Visayas: 45%, Luzon: 37.5%
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Region
o CARAGA: highest, 1.63%, Region 8: 1.5%
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Province
o Agusan Del Sur: highest with 3.95%
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Higher among males (occupational hazards)
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Higher among adults
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Occur with other helminthic infections
o STHs (Hookworms and Schistosoma same MOT)

Reported new foci in Cagayan valley and Negros Occidental (new endemic areas)

More common during wet months (snails more abundant during this time, people have more
contact with water)

DOC: Praziquantel
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For S. haematobium: alternative drug is Metrifonate
Schistosoma intercalatum
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Occurs in Western and Central Africa

Snail: Bulinus
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Eggs: similar to S. haematobium, there is curvature of the spine, presence of central-bulge
o Hour Glass in Appearance

Found in the stool
Schistosoma mekongki
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Eggs smaller than S. japonicum

Milder infection (similar manifestation with S. japonicum)

Intermediate hosts: Neotricula, Lithoglyphopsis

Found in Cambodia

Reservoir host: pigs
Avian Schistosomes – cause swimmer’s itch, lake itch, duck itch, Schistosoma of birds
o
Epidemiology
Treatment
Other Blood Flukes
76
N. Villanueva
LUNG FLUKES
PARAGONIMUS WESTERMANI
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Life cycle almost the same with the general life cycle
Ingest the crab with the metacercaria
Metacercaria released in the duodenum (excyst in the duodenum)
Penetrate intestinal lining (until it reaches the body cavity, peritoneal
wall)
Worms may not reach the lungs, may go to other parts of the body
(erratic)
Worm wanders then embeds itself in the abdominal wall
Then worm returns to coelom and migrates to pleural cavity
o Juvenile diploid worm wanders in the pleural spaces until it
finds one or several diploid worms
o Pair or group then migrates into the lung parenchyma to
develop into adults
o Juvenile triploid worms (Japan, Korea, Taiwan) can establish
themselves in the lung parenchyma without a mate
Found in sputum or feces
Embryonate in water
Miracidium passes through one sporocyst and two redial stages of development
Cercaria penetrates soft parts of crustacean and encysts as a metacercaria in the gills, body muscles, viscera, or legs
Immature worm traverses through intestinal wall into peritoneal cavity
Same banana
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Paragonimus westermani
Common name: Oriental Lung Fluke
Zoonotic: humans and other animals can serve as definitive and reservoir host
Habitat: lungs (encysted in lung tissue)
Paratenic host: boars (harbor larval stage)
Reservoir hosts: dogs, cats, field rats
1st intermediate host: Antemelania asperata (old name Brotia asperata) and Antemelania dactylus (snail)
2nd intermediate host: Sundathelphusa philippina, old name: Parathelphusa grapsoides (freshwater/mountain crab)
IS: metacercaria
MOT: ingestion of uncooked or undercooked crabs with metacercaria
P. siamensis: in PH, only been identified in cats
Cercaria: covered with spines, has an ellipsoidal body, and a small tail
o Stylet present at dorsal side of oral sucker

Life span of up to 20 years

Cysteine proteases: play an important role in development of young parasites (involved in metacercarial excystment, tissue
invasion, and immune modulation of the host)
o those with masses 27 and 28 kD: Cleaves IgG therefore creating a zone of immune privilege around the worm
o additional masses of 15, 17, and 53 kD are expressed as juvenile parasite moves towards the lungs
Adult worm

Reddish brown, coffee bean shaped

Rounded anteriorly and slightly tapered posteriorly

Found in pairs or threes in fibrotic capsules of the lung
o They undergo reproduction in pairs or in threes
o Capsule: small hole/covering where the egg will be released

Adult firmly attached to the lung tissue
o Can cause fibrosis (blood in lungs)
o Even if you cough, will not go out

Presence of spines on tegument (covering)

Intestinal ceca: wavy

Testes: lobed, usually 2
o Arranged in opposite (left and right)
o Important characteristic for parasite identification

Ovary: anterior to testes and posterior to ventral sucker, has six long unbranched lobes
Eggs

Golden brown, operculated, big and large

Ridge: opercular shoulder
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Presence of abopercular thickening (opposite operculum)
o Characteristic of Paragonimus
77
N. Villanueva
Immature when released
o Embryonates in water, moist soil, or leached feces
o Takes 2-7 weeks to embryonate
Lung Fluke Disease, Pulmonary Distomiasis, Endemic Hemoptysis, or Parasitic Hemoptysis, Paragonimiasis (signs
and symptoms mistaken for TB)

Early stages: asymptomatic

Heavy infections: dry cough/chronic cough, blood stained or rust colored sputum (fishy odor)

May mimic signs and symptoms of TB, chronic bronchitis, and bronchial asthma
o Living in an endemic area, have to be tested both for TB and Paragonimus

Erratic Paragonimiasis
o Aberrant or erratic worms
o Can go to heart and brain (brain: meningitis, seizures)
o Localization in the abdominal wall and cavity, mesenteric lymph nodes, pericardium, myocardium,
cerebral involvement may occur
o Cutaneous paragonimiasis: slow-moving, nodular lesion in subcutaneous tissue on abdomen or
chest is seen
o Cerebral paragonimiasis: migrate from pleural cavity to cranial cavity through the jugular vein, can
cause congestion, vasculitis, capillary rupture, infarction, hemorrhage, and necrosis

Pathology: adult worms provoke a granulomatous reaction (leading to formation of fibrotic encapsulation)

Chronic stage: liquefaction necrosis and fibrinous gliosis

Serious sequelae: chronic bronchiectasis and pleural fibrosis (secondary to severe parenchymal and
pleural damage)

Elevated eosinophils and IgE

Detection of eggs
o Stool: FECT, Kato-Katz
o Sputum

X-ray: nonspecific
o Appearance of TB and Paragonimiasis is the same in x-ray
o Focal areas in lung tissue
o Whitish part in the lung tissue

CT scan, MRI
o Characteristic finding: conglomerated, multiple, ring-enhancing lesions (grape-cluster
appearance)

Serology: complement fixation, intradermal test, ELISA, immunoblot
o Classic and well-known method: complement fixation

Find the complement-fixing antibodies

High sensitivity

Microscopy
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Double diffusion in agarose gel

Immunoelectrophoresis

Loop-mediated Isothermal Amplification (LAMP) test
o Rapid amplification of deoxyribonucleic acid under isothermal conditions
o Uses DNA polymerase with strand-displacement activity
o Magnesium pyrophosphate: reaction by-product

Preferred specimen: sputum
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Viscous, thick, and hard to process

Before examination, add mucolytic agent (3% NaOH)

Centrifuge after, examine sediment
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Lung biopsy can also be done (but invasive)
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Stool: can be examined if patient swallows sputum
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Global distribution of freshwater crabs
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Endemic areas: Japan, South Korea, Thailand, Taiwan, China, PH

Endemic Foci in PH: Leyte, Sorsogon, Mindoro, Camarines, Samar, Davao, Cotabato, Basilan,
Zamboanga del Norte, Davao Oriental

Pulmonary TB must be ruled out (especially in endemic areas)

PTB may coexist with Paragonimiasis

Transmission mainly due to food preparation practices

Dietary habits and presence of snail hosts could be related to endemicity
o Eat raw or undercooked crabs, juice of the crab

Reservoir hosts: dogs, cats, rodents

Paratenic hosts: boars and pigs

DOC: Praziquantel

Alternative drug: Bithionol

Disease
Diagnosis
Epidemiology
Treatment
78
N. Villanueva
INTESTINAL FLUKES
FASCIOLOPSIS BUSKI


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Life cycle starts with eating the water plant with the metacercaria
Metacercaria goes to duodenum, becomes adults here
Produce eggs, will be found in the stool
Eggs are unembryonated
Take 2 weeks to embryonate in fresh water
Miracidium penetrate snail
Same banana
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
Fasciolopsis buski
Common name: Giant Intestinal Fluke
Final host: humans
Reservoir hosts: pigs, dogs, rabbits
Habitat: Duodenum and jejunum (small intestine)
Largest intestinal fluke
1st intermediate host: Segmentina or Hippeutis
2nd intermediate host: water plants
o Trapa bicornis (water caltrop)
o Eliocharis tuberosa (water chestnut)
o Ipomea aquatica (water morning glory)
o Ipomea obscura (kangkong)
o Nymphaea lotus (lotus)
 IS: metacercaria
 MOT: ingestion of encysted metacercariae from aquatic plants
 Get infection if water plants are raw/undercooked
Adult Worms

Elongated, oval

Whitish in fresh specimen

Ventral sucker: larger than oral sucker

No cephalic cone (pyramidal structure)

Intestinal ceca simple and unbranched
o Reach up to posterior end

Dendritic testes arranged in tandem

Branched ovary, lies to right of midline

Fine vitelline follicles situated throughout lateral margin

Life span: 1 year
Eggs

Large and operculated

Indistinguishable from Fasciola

unembryonated

Hen’s egg appearance
Disease
Fasciolopsiasis

Parasite attached to small intestine

Pathology due to adult

Traumatic
o Inflammation and ulceration >> bleeding
o Gland abscesses in mucosa

Obstructive
o Heavy infections

Toxic
o Poisons people
o Worm metabolites
o Allergic reactions
o Death

Marked eosinophilia
79
N. Villanueva
Diagnosis
Epidemiology
Treatment

Malabsorption: of vitamins (B12)

DFS, FECT, Kato-Katz (eggs indistinguishable from Fasciola)

Patient history

Check eating habits

Clinical impression

Endemic in: South East Asia, China, Korea, India, Bangladesh

No local transmission yet

Reservoir hosts: pigs, dogs, rabbits
DOC: Praziquantel
ECHINOSTOMA ILOCANUM



Life cycle almost the same with general life cycle
Metacercaria excyst in the small intestine/duodenum
10 days for embryonation in fresh water

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
Echinostoma ilocanum
Common name: Garrison’s Fluke
Final host: humans
Reservoir hosts: dogs, cats, rats, pigs
Habitat: small intestine
1st intermediate host: Gyraulus convexiusculus and Hippeutis umbilicalis
2nd intermediate host: Pila luzonica (kuhol) and Vivipara angularis (susong pampang)
MOT: ingestion of metacercariae encysted in snails
IS: metacercaria
Adult Worms

Reddish gray, tapers at the posterior end (thinner)

elongated

Characteristic circumoral disk (with spines surrounding the oral sucker)
o 49-51 collar spines
o Aids in attachment
o Bloody diarrhea attributed to this

Testes deeply bilobed and in tandem

Intestinal ceca are simple and unbranched
Eggs

Straw colored or light brown, operculated, ovoid

unembryonated

Less prominent operculum, dot like appearance

size: Fasciolopsis bigger
Disease
Echinostomiasis

Inflammation at site of attachment

Heavy infections
o Diarrhea (bloody) and abdominal pain

Intoxication: metabolites (causes poisoning)
Diagnosis
Egg (from stool)

FECT, Kato-Katz (eggs resemble F. buski, smaller compared to F. buski)
Epidemiology

Endemic in: Northern Luzon, Leyte, Samar, provinces in the Philippines, Ilocos

High incidence in rainy weather

Eating habits and practices

2nd intermediate host abundant in rice paddies during the rainy season

Important Reservoir hosts: rats
Treatment
DOC: Praziquantel
80
N. Villanueva
Artyfechinostomum malayanum

Similar to E. ilocanum

Adult worms are bigger
o Possess 43-45 collar spines
o 2 large testes (6-9 lobes in tandem)

Eggs: larger, golden brown, operculated

1st intermediate host: unknown (only known that it’s a snail, species is unknown, but it is similar to
Echinostoma)

2nd intermediate host: Lymnaea cumingiana (birabid)
o Ampullarius canaliculatus
HETEROPHYID WORMS



Collective group of worms
Minute fish borne flukes (freshwater fish)
Major species: Heterophyes heterophyes, Metagonimus
yokogawai, Haplorchis yokogawai, Haplorichis taichui
o In country: M. yokogawai and H. taichui
H. heterophyes: smallest fluke (not found in PH)
Wide range of intermediate hosts (FISH)
life cycle: embryonated egg ingested by the snail
o egg hatches inside the snail




Heterophyid worms
Final host: man, birds, various fish-eating mammals

MOT: ingestion of encysted metacercariae in fish
 Habitat: small intestine
 1st intermediate host: brackish water or marine species snails
o Melania juncea: H. taichui
o Pironella: H. heterophyes
o Semisulcospira: M. yokogawai
o Procerovum calderoni: Thiaria riquetti (from the book)
 2nd intermediate host: brackish and salt water fish; tilapia
o Mugil cephalus (mullet, for H. heterophyes)
 IS: metacercaria
 Metagonimus yokogawai: Most common intestinal fluke in SEA or Far East
Adult worms

Elongated, oval, or pyriform (pear-shaped)

Very small

Tegument: fine scale like spines

Third sucker (gonotyl) seen in H. heterophyes

Testes arrangement is varied (depends on species)

Ovary is globular or lobed

Short life span (<1 year)

Metagonimus yokogawai
o Testes: large and oval (2)
o Bit larger than H. heterophyes
Eggs

Light brown color, ovoid, operculated, small

Embryonated

No abopercular protruberance

H. taichui: light striae pattern
Disease

local inflammation at site of attachment
81
N. Villanueva
colicky pain and mild diarrhea
peptic ulcer diseases and acid peptide disease
burrow deep into the intestinal wall (because they are very small)
o eggs can be spilled into the blood stream and carried to different parts (brain, spinal cord,
heart) forming granulomas
o can lead to extra-intestinal infections

deposition of eggs in vital organs (heart, brain, spinal cord)

diagnosis most of the time after death
Egg (from stool)

FECT, Kato-Katz (more efficient)

Difficult to distinguish

No abopercular protruberance
Adults

Autopsy

Cardiac heterophydiasis: mistaken as Cardiac Beri-beri

Worldwide distribution

Egypt, Greece, Israel, Western India, Central and South China, Japan, Korea, Taiwan, Philippines

Fish-eating countries

Nonspecific to its hosts

Reservoir hosts: Dogs, cats, birds

Locally: low prevalence and spotty
o Compostella valley: 31% prevalence (mostly due to H. taichui)
o Emerging public health problem
o Cases come from provinces in Mindanao

DOC: Praziquantel

Thorough cooking of fish

Proper sanitation

Health education



Diagnosis
Epidemiology
Treatment and
Prevention and
Control
Other intestinal Flukes

Gastrodiscoides hominis
o Final host: man
o Reservoir host: pigs
o Habitat: colon
o 1st intermediate host: Helicorbis coenosus
o 2nd IH: water plants
o Adult worm

Pink/bright pink in appearance

Conical anterior portion

Prominent and notched ventral sucker
o Eggs: operculated, immature, greenish brownish
o Disease: asymptomatic in light infections, mucus diarrhea in heavy infections (abundance of mucus in stool)
o Found in Asia and India
LIVER FLUKES
FASCIOLA SPP.


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
Metacercaria released to the duodenum
Larva penetrate and burrow in the small intestine
Reaches wall of small intestine and goes to wall of body cavity
Then migrates to liver (goes inside the Glisson’s capsule)
o Eggs from adult goes to intestine via the sphincter of Oddi
Attached to the liver and bile duct (using their suckers)
Eggs in stool (immature)
Embryonation in water (9-15 days)
Eggs hatch and release miracidium, miracidium goes to snail
Same banana
82
N. Villanueva



Fasciola
Final host: sheep, cattle, and other herbivores (humans infected occasionally)
Habitat: biliary passages of liver
1st intermediate host: Lymnaea philippinensis and L. auricularia rubiginosa
o From the book:
 Europe and North Asia: Lymnaea truncatula
 North America: Lymnaea bulmoides
 Australia: Lymnaea tomentosa
 Indian subcontinent: Lymnaea acuminate
 Africa: Lymnaea natalensis
 2nd intermediate host: Aquatic plants
o Ipomea obscura (kangkong, swamp cabbage)
o Nasturtium officinale (water cress)
 MOT: ingestion of undercooked or raw aquatic plants containing the metacercaria
 Eggs reported as Fasciola egg
 F. hepatica: found in cold and temperate countries, also found in sheep and herbivores
 F. gigantica: more common in tropical countries
 very few among humans
o have economic implications (livestock)
F. hepatica
F. gigantica
Common name
Sheep Liver Fluke, Temperate Liver Fluke
Tropical liver fluke
Adult Worms

Large broad, flat body

Longer but narrower (slender)

Cephalic cone and prominent shoulders

Shorter cephalic cone and less developed
shoulders

Intestinal ceca highly branched

Testes: branching

Testes (2): highly branched, no longer
described because highly branched

Ovary: branches longer and more numerous

Ovary: dendritic

Uterus: coiled and short
Eggs

Large, ovoidal

Bigger

Brownish

Operculated

Immature when released

Contains large mass of vitelline cells
Disease
Fascioliasis

Acute stage: larval migration and Worm maturation
o Fever, jaundice, pain, anorexia, hepatomegaly

Jaundice due to obstruction in the bile ducts

Impedes flow of bilirubin to the intestines, bilirubin accumulates in the liver

Causes yellowing of skin and sclera of eyes

Not a disease, only a sign
o Triad of high fever, hepatomegaly and marked eosinophilia

Three important manifestations
o Occurrence of liver rot

Among animals

Tissue destruction of liver

Chronic stage: persistence of the adults in the biliary ducts
o Obstruction and inflammation leading to fibrosis or cirrhosis

Other complications: hemobilia, biliary cirrhosis, lithiasis of bile ducts or gall bladder, acute pancreatitis

During migration from intestine to liver, parasite may wander or be carried by the blood to ectopic sites
(lungs, subcutaneous tissue, brain, etc.)

Halzoun/Marrara: temporary lodgement of the fluke in the pharynx
o Ingestion of raw liver (flukes still there)
o Mediterranean countries
o Obstruction of pharynx (attached to the pharynx), leads to suffocation

Pseudofascioliasis
o Spurious infection (not true infections)
o Ingestion of livers (cooked) containing eggs
o False positive infection (the eggs won’t hatch)
o Remedy: liver free diet for 3 days
Diagnosis

Egg (from stool)
o FECT, Kato-Katz
o Difficult to distinguish from F. buski
83
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
Epidemiology
Treatment
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
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
N. Villanueva
o Report as Fasciola egg
Serology: low specificity
o ELISA, Western Blot
Molecular methods: RFLPs (Restriction Fragment Length Polymorphism)
o Exploits variations in homologous DNA sequences
Radiography
o CT scan: multiple confluent, hypodense nodules, and tunnel-like branching hypodense tracts
o Hepatic sonography: small clustered hypoechoic lesions with poorly defined contours and
hypoechoic nodular lesions

Oval-shaped, leaf-like, snail-like echogenic structures with no acoustic shadowing
Endoscopic retrograde cholangiopancreatography (ERCP)
Laparotomy
Diet History
Worldwide distribution
Estimated 2.4 million people affected excluding Asia
80 million at risk of infection
F. gigantica dominant species locally
human infections are sporadic
Reservoir hosts: hares and rabbits
no data on disease burden in Asia
Vietnam: increased number of cases
DOC: Triclabendazole
Bithionol
CLONORCHIS AND OPISTHORCHIS

Life cycle: embryonated egg ingested by snail immediately
o Miracidium hatches only after egg is ingested by first intermediate host
Metacercaria released in small intestine, goes to body cavity, goes to habitat (through ampulla of Vater), becomes adults
Eggs already embryonated once released


Clonorchis








Opisthorchis
Clonorchis and Opisthorchis
Parasites of bile duct and gall bladder
Fish borne
Prevalent in South East Asia, China, Japan, Korea (fish eating countries)
Habitat: bile ducts and bile passages, pancreatic duct, can also be found in gall bladder
MOT: ingestion of raw or undercooked fish containing metacercaria
Final host: humans
Reservoir hosts: cats, dogs, pigs, other mammals (fish eating animals)
C. sinensis 1st IH: Parafossarulus, Bulinus, Semisulcospira, Alocinma, Thiara, Melanoides
84
N. Villanueva
Opisthorchis 1st IH: Bithynia
2nd IH: Cyprinoid fresh water fish (fish of Family Cyprinidae)
C. sinensis: most important liver fluke of man
Adult worms feed on tissue fluids, red blood cells, and mucus
o They are also leaf-like in shape, with transparent tegument
o Vitellaria: found in the middle third of the body (at level of uterus)
Clonorchis
Opisthorchis
Common name
C. sinensis: Chinese/Oriental Liver Fluke
O. felineus: Cat liver fluke
O. viverrini: Siberian Liver Fluke
Adult Worms

Flat, transparent, elongated, rounded

Elongated and spatulate
posteriorly

Ventral sucker bigger than oral sucker

Attenuated anteriorly

Intestinal ceca: simple

spatulate in appearance

O. felineus: reddish brown, paired, lobate

Deeply branched testes arranged in tandem
testes arranged obliquely in tandem (with an
angle)

Lobed ovaries

O. viverrini: deeply lobulated ovaries and

Intestinal ceca are simple and unbranched
testes (in tandem)

Largest oral sucker among other flukes
Eggs

Yellowish brown, ovoid

Distinct convex operculum
o Presence of opercular shoulder

Presence of abopercular protruberance (opposite operculum)

Old fashioned bulb or pitcher shape

Similar egg: H. heterophyes (but Heterophyes does not have the abopercular protruberance)

Indistinguishable from other species

Mature when passed (embryonated)

O. viverrini: distinct melon-like ridges
Disease
Clonorchiasis and Opisthorchiasis

Acute infection
o Fever and chills, fatigue, weakness, weight loss, liver enlargement, jaundice, eosinophilia

Parasite in the bile duct and liver, causes obstruction and fibrosis
o Due to constant inflammation and irritation

Chronic infection
o Periductal fibrosis
o Cirrhosis and portal hypertension
o Perforation of gall bladder

Damage may be due to mechanical or chemical irritation or immune mediated

Gall stone formation

Enhanced susceptibility to: Cholangiocarcinoma (Bile Duct Carcinoma)
o After many years of infection

Phases of Clonorchiasis
o Desquamation of epithelial cells
o Hyperplasia and desquamation of epithelial cells
o Hyperplasia, desquamation of epithelial cells, and adenomatous tissue formation
o Marked proliferation of periductal connective tissue (with scattered abortive acini of epithelial
cells and fibrosis of wall of biliary duct)

C. sinensis: probable carcinogen
Diagnosis

Egg (from stool)
o FECT, Kato-Katz
o Cannot be distinguished from each other
o Duodenal aspirates, entero-test
o Can use permanganate to stain the eggs
o Stoll’s Dilution (check lab handout nung first shift)

After the no. of eggs per gram (like Kato-Katz)

Used when processing more amount of stool

Serology
o ELISA (detect secretory antigens)

Molecular methods: PCR

Radiological features of biliary clonorchiasis
o Saccular dilatations of intrahepatic bile ducts
o Rapid ductal tapering toward periphery
o Arrowhead sign
Epidemiology

C. sinensis
o Endemic in China, Korea, Japan, Vietnam




85
N. Villanueva

Treatment
O. felineus
o Europe, Turkey, Russia, Korea, Japan, Vietnam, India

O. viverrini
o Thailand, Laos, Malaysia

Fish-eating countries

Khon Kaen Northeast Thailand: highest incidence of cholangiocarcinoma

Still common in Laos (85% prevalence)

Food habits and cultural practices

Higher in men

No local transmission
DOC: Praziquantel
DICROCOELIUM DENDRITICUM




MOT: ingest ant
Metacercaria excysts in the duodenum
Penetrates the intestine, goes to the bile duct, gall bladder, and liver
Metacercaria becomes an adult worm, produces eggs, eggs goes to
stool
Egg already embryonated once released
Egg is ingested by the snail, release miracidium
Miracidium develops into cercaria, no redia stage
Cercaria released in via respiratory tract of snail
o In the form of slime balls







Dicrocoelium dendriticum
Common name: Lanceolate Fluke or Lancet Fluke
AKA: Fasciola dendriticum or Fasciola lanceolata
Final host: herbivores (ruminents), humans may also be infected
o Among cows, sheep, and cattle
o Humans just accidental hosts
 Habitat: Bile Duct, Liver
 1st intermediate host: Cionella lubrica (snail)
 2nd intermediate host: Formica fusca (ants)
 MOT: ingestion of ants containing metacercaria
Adults

Blade like, lancet like

Aspinous (no spines on tegument)

Testes: located in anterior 1/3

Ventral sucker bigger than oral sucker
Eggs

Dark brown, thick shelled, large operculum

Embryonated
Disease

usually asymptomatic

Symptoms appear if you ingest more ants

heavy infections: enlargement of bile ducts and hyperplasia of epithelium, may lead to cirrhosis
Diagnosis
Stool exam
Treatment
DOC: Praziquantel
86
N. Villanueva
PANCREATIC FLUKE
EURYTREMA PANCREATICUM


Life cycle almost same with lanceolata
Embryonated egg released in stool







Eurytrema pancreaticum
Pancreatic fluke
Final host: hogs, sheep, goat, cattle
Accidental host: human
Habitat: biliary ducts and pancreatic ducts
1st IH: Macrochlamys indica (snail
2nd IH: Technomyrmex deterquens (ant), Grasshoppers
MOT: ingest ant or grasshopper with metacercaria
Adult Worms

Leaf shaped

Ruffled border or body margin

2 notched testis

1 notched ovary
Eggs

Similar to lancet fluke

Operculated

Embryonated once released
Disease
Eurytremiasis

Destruction of pancreas
o Can cause Type I Diabetes Mellitus

Chronic granulomatous pancreatitis

Enlargement of pancreas
Diagnosis
Stool exam (egg)
Treatment
DOC: Praziquantel
87
N. Villanueva
88
N. Villanueva
89
N. Villanueva
CESTODES










Phylum Platyhelminthes, Class Cestoda
Cestode: comes from Greek word meaning “girdle” or
“ribbon”
o Have a tape/ribbon like appearance
Tapeworms
Adult worms appear as flat and ribbon like
All are monoecious (hermaphrodites)
No mouth and gastrointestinal tract
o Obtain nutrients via absorption and diffusion through
their tegument
Adult worms inhabit the small intestine
Eggs are non-operculated, embryonated
o Except for Diphyllobothrium latum (operculated and
unembryonated)
Fresh specimens appear whitish/creamy
Tegument – body covering
o Glycocalyx – carbohydrate rich, useful for protection
o Possess microthrices (microthrix)

Similar to microvilli, useful for absorption
For D. latum (has two bothria, hence
Diphyllobothrium)

No rostellum, no hooks, no suckers
Rostellum – protruding structure where hooks are
attached

Armed – has hooks/hooklets

Unarmed – no hooks

Not all tapeworms have rostellum
Neck – region of growth, where proglottids arise
Proglottids: tapeworm segments

Immature

Most proximal (closest to neck)

Still developing, no reproductive structures

Mature

Presence of well-developed reproductive
structures

Uterus, ovaries, testes, vitellaria, vas
deferens (which connect to the genital pore)

Gravid/Ripe

Most distal from neck

Filled with eggs

Testes and ovaries sometimes not seen
Strobila – chain of proglottids

Strobilization/strobulation (process of formation of
proglottids)

o
o
o
o
Mitochondria and basal lamina (not elaborated
anymore)
o Proximal – muscles of tegument
o Distal – presence of mitochondria
Scolex – attachment organ, holdfast organ
o Used by parasite to attach to small intestine
o Acetabulate (Acetabulum)

Cuplike suckers

2 in front, 2 at the back

Aid in attachment

Found in true tapeworms
o Bothriate (Bothrium)

slit-like groove or depression

Spoon, spatulate, almond-shaped
o

90
N. Villanueva
TWO ORDERS OF TAPEWORMS
Scolex
Order Pseudophyllidea (False Tapeworm)
*D. latum only important member

Spoon, almond, spatulate

2 slit like grooves (bothria)

No rostellum and no hooks
Order Cyclophyllidea (True Tapeworm)


Quadrate (square-like)
May possess rostellum
o Not all true tapeworms have
o T. saginata: without rostellum

4 cup like suckers
Apolytic

Proglottids able to detach
Strobila
Anapolytic

Proglottids unable to detach
Vitellaria (for egg shell
production)


Diffused with many follicles
Dispersed, not compact
Compact and separate
Gravid Proglottid


All reproductive organs still present
Rosette uterus


Degenerate reproductive organs
Only uterus and its lateral branches seen
Uterine Pore



Present
Median ventral surface
Where eggs exit (connected to uterus)


Absent
Eggs go out through the genital pore (located
on the side or laterally)
Ova



Oval
Operculated
unembryonated



Spherical
Non-operculated
Embryonated
Larval Stages



Coracidium
Procercoid
Plerocercoid




Only 1 (depends per species)
Cysticercus
Cysticercoid
Hydatid cyst
Intermediate Hosts



1st: Copepods
2nd: Freshwater fish
More complicated life cycle


1 IH: lower forms of animals, arthropods, man
Only 1 (but some do not require intermediate
hosts, like Hymenolepis nana)
91
EGGS


N. Villanueva
Egg becomes coracidium then Procercoid
o Procercoid more elongated
o Cercomer located on distal part of Procercoid

Used for attachment

Has 6 hooklets
Procercoid becomes Plerocercoid
o Infective stage to humans
o Found in fish
o Causes Sparganosis (called the sparganum) –
larval invasion, multi-organ infection
LARVAL STAGES: CYCLOPHYLLIDEA




False tapeworms (a)
o Operculated
o Coracidium located inside

Motile and ciliated
o Oncosphere – contains embryo

Usually described as hexacanth embryo
(embryo has 6 hooklets)
o Inner envelope – surrounds oncosphere
o Ciliated embryophore – surrounds inner envelope
o Outer envelope – surrounds ciliated embryophore, in
between egg shell and ciliated embryophore
Typical egg of Dipylidium caninum (Dipylidean), (b)
o Shell – outermost
o Outer envelope
o Embryophore – not ciliated
o Inner envelope
o Oncosphere with hexacanth embryo
Typical egg of Taenia spp. (c)
o No shell
o Embryophore – striated
o Inner envelope
o Oncosphere with hexacanth embryo



Cysticercus – for Taenia spp.
o Common term: bladder worm (bladder-shaped
structure surrounding the protoscolex)
o Protoscolex is invaginated
o Protoscolex eventually becomes scolex
Cysticercoid – for Hymenolepis, Dipylidium, etc.
o Has 6 hooklets located on distal portion
Coenurus – larva is invaginated
Hydatid cyst – for E. granulosus
o Contains daughter cysts
o Protoscolex located inside
ORDER PSEUDOPHYLLIDEA
DIPHYLLOBOTHRIUM LATUM
LARVAL STAGES: PSEUDOPHYLLIDEA
92
N. Villanueva
Life Cycle
Ingest raw or undercooked fish
Adult tapeworm produces eggs
Egg goes to freshwater
Copepods (Cyclops) ingest coracidium
Plerocercoid larva found in fish



Plerocercoid larva released, goes to small intestine

Plerocercoid larva attaches to lining of small intestine

Larva becomes adult tapeworm
Prolific parasite: produces around a million eggs
Eggs and proglottids found in the stool (egg is unembryonated)

Takes 7-10 or 8-12 days to embryonate

Egg hatches to release coracidium

Coracidium becomes procercoid larva inside copepod

Copepod ingested by another fish

Becomes plerocercoid larva inside

Ingested by humans
Diphyllobothrium latum

Common name: Broad or Fish Tapeworm (one of largest and longest tapeworms, can become 10-25 meters)

Final Host: Man

Reservoir host: Dogs, cats, other fish-eating mammals

Paratenic Host: Carnivorous Fish (can eat small fish with the larva)

Habitat: small intestine (ileum)

1st Intermediate host: Copepods (Cyclops and Diaptomus)

2nd Intermediate host: Freshwater fish (salmon, trout, pike, ruff, perch, etc.)

Infective stage: Plerocercoid

Diagnostic Stage: Egg

MOT: ingest raw, undercooked, or pickled freshwater fish with plerocercoid
Adult Worm

Presence of rosette uterus

Whitish/milkish

Scolex: Bothriate (two, located ventrally and dorsally)

Proglottids disintegrate only when segment has completed its reproductive function
Egg

Operculated and unembryonated

Opposite operculum: knob-like thickening

Mistaken for P. westermani
o Both operculated
o Size: Paragonimus bigger than Diphyllobothrium
o Paragonimus: contains abopercular thickening
o Paragonimus is asymmetrical, Diphyllobothrium is symmetrical
o Paragonimus have the opercular shoulder, Diphyllobothrium
does not have
Disease
Epidemiology
Diagnosis
Treatment and
Prevention
Diphyllobothriasis

Asymptomatic in most persons

Obstruction, diarrhea, or anemia have been reported
o Heavy infections: Megaloblastic Anemia due to deficiency of vitamin B12

Hyperchromic, with thrombocytopenia and leukopenia
o Anemia mistaken for Pernicious anemia (B12 deficiency)
o Bothriocephalus anemia vs true pernicious anemia

Both cases: large RBCs on blood smears

Test for Achlorhydria (absence of HCl in gastric secretions), only found in pernicious

Pernicious anemia: autoimmune disease due to problem with parietal cells

Nonspecific abdominal symptoms

Occurs in Northern Temperate Areas where raw, pickled, or inadequately cooked fish are eaten

Found in fish-eating countries (Finland, Japan, Europe, Chile, North America, Norway)
o Especially in Scandinavia

Finnish people: genetic predisposition to Pernicious anemia

Demonstration of Eggs (FECT, Kato-Katz DFS)

Demonstration of Proglottids

Travel history and diet (may suggest Diphyllobothriasis)

DOC: Praziquantel

Niclosamide: may be used, but side effects may be seen

Cook fish thoroughly

Store fish properly (Can kill it at a very high and very low temperature, -18C kills plerocercoid larva)

Environmental sanitation and Health Education
93
N. Villanueva
Sparganosis

Due to larval forms of D. latum and Spirometra

Humans are technically intermediate hosts here
o We ingest infective stage inside Cyclops (larval forms, procercoid is accidentally ingested)
o Ingestion of raw infected flesh of amphibians and reptiles

Procercoid becomes plerocercoid inside the human

Plerocercoid also known as Sparganum

Larval stages of parasite are recovered in the different organs

May cause local inflammation and eosinophilia

May also get sparganosis if fond of eating raw pork, meat, amphibians, frogs, herbal medicine

Diagnosis: surgical removal of worms

Treatment: Surgery, Praziquantel
ORDER CYCLOPHYLLIDEA
TAENIA SPP.
Life Cycle
MOT

T. solium: ingest pig

T. saginata: ingest cattle
Pig and cattle ingest egg
Cysticercosis






Cysticercus goes to small intestine (attaches here)
Proglottids and eggs seen in stool sample
Oncosphere is released
Oncosphere attaches to the muscle, becomes Cysticercus
Humans accidentally ingest egg
Oncosphere released and deposited to different vital organs (muscle, brain)
94
N. Villanueva



Taenia spp.
T. solium, T. saginata, T. saginata asiatica (common in Asian countries, PH and Taiwan)
Final Host: Humans
Habitat: small intestine
T. solium
T. saginata
Common name
Pork Tapeworm
Beef Tapeworm
Intermediate Host
Pigs, Humans (during Cysticercosis)
Cattle (humans not an IH, no Cysticercosis)
Infective Stage
Cysticercus cellulosae (armed)
Cysticercus bovis (unarmed)

Also known as the Bladder Worm

Also called Bladder Worm

Egg also infective (during Cysticercosis)

Cysticercus cellulosae found in pork (pork is
referred to as “Measly Pork”)

Egg can be found in salad and vegetables
MOT
Ingestion of measly pork or egg
Ingestion of raw or undercooked beef
Adult Worm

Globular scolex

Whitish opaque

Armed rostellum (2 rows of hooks, each row

Cuboidal
with 25-30 hooks)

Longer (4-10, up to 25 m)

Short neck

No rostellum

Length: 2-3 meters, up to 8 meters
Proglottid
Mature Proglottid
Mature Proglottid

Ovary: Trilobed ovary

Wider than tall (“Squarish”)

Smaller number of testes
Gravid Proglottid

Only uterus seen

5-13 lateral uterine branches (finger-like)

Square shaped

Ovary: Bilobed

Testes more scattered

Uterus: median, club-shaped

Vagina has a sphincter (book)

Genital pore: irregularly alternate
Gravid Proglottid

Longer than wide

15-20 tree-like uterine branches
*proglottids less active than T. saginata (not observed
to crawl about)
Egg
Disease

Indistinguishable (reported as Taenia spp. egg)

Spherical brown and radially striated

Oncosphere with 6 hooklets

Original thin outer membrane surrounding egg rarely retained after passage from proglottid
Taeniasis solium

Asymptomatic in most persons

Vague abdominal discomfort, hunger pangs, chronic indigestion

Problem if Cysticercosis
o Larva deposited to different to vital organs (skeletal muscle, brain)
95
o
o
o
o
o
o
o
o
Epidemiology
Diagnosis
Treatment and
Prevention
N. Villanueva
Accidental ingestion of eggs (food and drink)
Autoinfection: eggs can hatch inside and go back
Severe disease caused by T. solium
Most common parasitic disease of CNS (Neurocysticercosis)
Common in Mexico
Subarachnoid form: may lead to an aggressive form called Racemous Cysticercosis

Characterized by formation of cysts in base of brain

Poor prognosis
Intraventricular form: leads to obstructive hydrocephalus
Can also affect eyes (Chorioretinitis and vasculitis)
T. saginata

NO CYSTICERCOSIS

Usually asymptomatic

Vague abdominal pains, obstruction

By-products of worm: systemic intoxication

Individual proglottids actively motile
o Cause obstruction in bile and pancreatic ducts, and appendix
T. solium

Eating habits

Religious beliefs (Muslims don’t eat pork)

Prevalence of Taeniasis solium relates to number of cases of cysticercosis

Worldwide distribution (areas where pork is consumed or raised)

Central and South America (MEXICO), Africa, South East Asia, Eastern Europe, Micronesia
T. saginata

More common among alcoholic males

Common in Northern Luzon

Common in cattle raising countries (Africa, Middle East, Central and South America, Asia)

Cultural and religious beliefs (Hindus do not eat cattle)

More common in PH
Coproantigen Detection: ELISA, Molecular Methods
T. solium

Cysticercosis
o surgery
o CSF analysis (will not recover parasite, only see increase of WBCs and other proteins)
o X-ray, CT, MRI
o Detected primarily by serologic tests
o Basis: Neurologic disorders, neuroimaging, travel history
o Gold standard: Immunoblot using purified Glycoproteins (Western Blot)

Antibodies against cysticercal antigens (IgG and IgM)

CDC recommendation
o ELISA, Molecular methods
T. saginata

Stool exam (DFS, Kato-Katz, FECT) to look for eggs (Indistinguishable)

Proglottids: Number of uterine branches
o Double Slide Compression Technique
o Use of India Ink or Carmine to visualize
o Carbol xylol: clearing agent to make segment transparent
o India ink or carmine injected into genital pore (connected to uterine branches)

Scolex recovered after treatment/recovery (indicates you are cured)

Can also use scotch tape swab
*eggs irregularly passed out with stool, FECT increases chances of demonstrating eggs

Praziquantel

Niclosamide

Surgery (Cysticercosis)
o Praziquantel and Albendazole
o Corticosteroids
o Avoid Niclosamide and Dichlorhen (disintegration of segments)

Criteria for cure
o Recovery of scolex
o Negative stool exam 3 months after treatment

Thorough cooking of meat
o At -20C for 10 days kills the cysticerci
o At 65C

Proper sanitary meat inspection
96
N. Villanueva

Proper waste disposal

Personal hygiene

Case finding and chemotherapy

Health education
Taenia saginata asiatica

Asian Tapeworm, Hybrid Tapeworm

First reported in Taiwan

Prevalent in Asia

Cysticercus called cysticercus viscerotropica (has wart-like protruberances)

Quite difficult to differentiate from T. saginata

Scolex similar to T.solium
o Scolex devoid of hooklets but there is a prominent rostellum

Sister species of T. saginata (proglottid looks like T. saginata, may be misidentified as T. saginata)

Mature proglottids carry a vaginal sphincter

Gravid proglottid have a posterior protruberance

Found in Taiwan, China, Korea, Indonesia, Philippines, Vietnam, Thailand

Found in the liver of pigs (instead of muscles)

Do not cause cysticercosis

Intermediate hosts quite varied aside from pigs
HYMENOLEPIS SPP.
Life Cycle
MOT: accidental ingestion of flea or
beetle
Stool: eggs and proglottids
Eggs released inside IH
*H. nana autoinfection
*Direct life cycle: ingestion of egg
H. nana








Larva released, larva attaches to small intestine
o Becomes adult worms here
Goes to environment
Ingested by IH
H. nana: sometimes IH not needed
o Indirect life cycle: requires IH
o Direct life cycle: does not need IH
H. diminuta: only has indirect life cycle (only IS: cysticercoid larva)
Becomes Cysticercoid larva
Accidentally ingests proglottid containing embryonated eggs
Becomes larva then adult in small intestine
H. diminuta
97
N. Villanueva
Hymenolepis spp.

H. nana
o Smallest tapeworm of man (25-40 mm)
o Most common cestode infection
o Final Host: Humans

H. diminuta
o Final Host: Rat
o Accidental host: humans

Habitat: small intestine (upper portion of ileum)

MOT: ingestion
H. nana
Common name
Dwarf Tapeworm
Intermediate Host
Wide variety of insects

Ctenocephalides canis (Dog Flea)

Pulex irritans (Human Flea)

Xenopsylla cheopsis (Rat Flea)

Tenebrio (Rice Beetle)

Tribolium (Flour Beetle)
Infective Stage
2 infective stages

Cysticercoid (indirect)

Embryonated egg (direct)
Adult Worm

Scolex
o Subglobular or rhomboidal
o Armed rostellum (20-30 y shaped
hooklets in a single row)

Neck: long and slender
Proglottid
Mature Proglottid
H. diminuta
Rat Tapeworm
Variety of arthropods

Cockroach

Rat flea

Flour moths

Flour beetles
Cysticercoid larva


Larger than H. nana
Scolex
o Knob shaped
o Unarmed rostellum
Mature Proglottid

3 ovoid testes

1 ovary

60 mm (longer than H. nana)
Gravid Proglottid


3 ovoid testes
1 ovary (bilobed)
Egg




Circular and thin-shelled
Oncosphere with hexacanth embryo (6
hooklets)
Polar thickenings
Polar filaments (4-8) emanating from
thickenings






Bigger and larger
Bile-stained
Striated shell
Hooklets: fan-like arrangement
Presence of polar thickenings, but no polar
filaments
Fried egg appearance
98
N. Villanueva
Larva
Same lang (cysticercoid)
Disease
Epidemiology
Diagnosis
Treatment
H. nana

Wala lang

Usually asymptomatic

Patients may complain of headache, dizziness, anorexia, pruritus of nose and anus, diarrhea,
abdominal pain

Infected children: may appear restless, irritable, sleep disturbances
o Infections in children resolve spontaneously in adolescence

Heavy infections: enteritis due to necrosis, desquamation of intestinal epithelial cells

Regulatory immunity may limit or eventually clear H. nana population spontaneously
H. diminuta

Wala lang

Humans just accidental hosts

Minimal and non-specific
H. nana

Children usually infected

Found in warm countries, poor countries, and where sanitation is poor

Species in mice and rats: H. nana var. fraterna
H. diminuta

Worldwide distribution

More common among children

Infection usually occurs in poor areas with rats

Stool exam (look for eggs)
Praziquantel
DIPYLIDIUM CANINUM
Life Cycle
Dog accidentally
ingest flea with
cysticercoid larva
Stool: proglottids
with eggs
Flea ingests egg








Larva released, attach to small
intestine
Larva becomes adult worms
Eggs enclosed in egg packets

Eggs becomes cysticercoid larva
Dipylidium caninum
Double Pored Tapeworm, Dog Tapeworm, Flea Tapeworm, Cucumber Tapeworm
o Proglottid looks like cucumber
Final Host: dogs, cats
Accidental host: man
Habitat: small intestine
Intermediate hosts
o Ctenocephalides canis
99
N. Villanueva
o Ctenocephalides felis
o Book: also includes Pulex irritans (human flea) and Trichodectes canis (dog louse)

Infective stage: cysticercoid larva

MOT: ingestion
Adult Worm

Scolex
o Conical
o 4 suckers
o Retractable armed rostellum (with several rows of hooks)

1-7 rows of rose thorn-shaped hooklets
Proglottid
 Two genital pores on each side (left and right)
 Has 2 sets of reproductive organs (2 of each)
 Gravid proglottid: looks like a cucumber (size and shape of pumpkin seed)
 Also barrel-shaped



Egg
Disease
Epidemiology
Diagnosis
Treatment
Enclosed in egg packets
1 packet: 8-15 egggs (can contain up to 25)
1 egg: spherical and radially striated

Wala lang

Asymptomatic

Abdominal pain, anal pruritus may occur (heavy infections)

Common in small children

Look for egg packets (rare) or proglottid in stool or perianal area
Praziquantel
RAILLIETINA GARRISONI












Raillietina garrisoni
Can be spelled either Raillientina or Raillietina
Aka Raillietina madagascariensis
Madagascar Worm
Common tapeworm of rats
Belongs to family Davaineidae
Final host: rats
Accidental host: man
Habitat: small intestine
Intermediate host: Tribolium confusum (beetle)
Infective stage: Cysticercoid larva
MOT: ingestion
Life cycle similar to Hymenolepis
100
Adult Worm

Proglottid
Scolex
o
o
o
o


Disease

Wala lang

Asymptomatic

Children usually affected (proglottids usually passed out)

Stool exam (proglottids or ova)

Common cestode of rodents in the Philippines

Infections usually occur due to ingestion of infested grains

Children less than 3 years old are affected
Praziquantel
Treatment

N. Villanueva
Gravid proglottid: rice grain
appearance
Subglobular
Armed rostellum
2 alternating rows of hammer shaped
hooklets
Several rows of spines also surround
rostellum
Egg
Diagnosis
Epidemiology

Enclosed in egg capsule
Spindle-shaped in appearance
ECHINOCOCCUS SPP.
Life Cycle
Dog: ingest
hydatid cyst


Stool of dog:
proglottids and
eggs


Hydatid cyst goes
to vital organs
(liver and lungs)











Hydatid cyst goes to vital organs
Protoscolex inside will attach to
small intestine and become adult
worm
Eggs ingested by IH
Eggs hatch and release
oncosphere
Oncosphere becomes hydatid cyst
Human: dead-end host
Echinococcus granulosus
Other species: E. multilocularis, E. vogeli
Hydatid Worm
Smallest tapeworm of dogs (3-6 mm)
Belong to family Taeniidae
Final host: Canines (Dogs)
Habitat: small intestine
Intermediate host: sheep, goat, swine, cattle, horses, camel, humans (accidental)
Infective stage: hydatid cyst
MOT: ingestion
101
Adult Worm
 Scolex
o Pyriform
o Armed rostellum
o 4 suckers
 Proglottid: composed of
3 proglottids only (immature,
mature, and gravid)
Egg
N. Villanueva
 Similar to Taenia
Hydatid cyst



Disease
Epidemiology
Macroscopic structure (as big as a ping pong ball, 20 cm in diameter)
Deposited in liver and lungs
Different layers
o Outer layer: adventitial/collagen layer (not actual cyst, part of the IH)
o Laminated layer: hyaline
o Germinal layer: innermost, nucleated

Daughter cyst: small version of the whole hydatid cyst
o Everything in hydatid cyst is also found inside
o Can also become brood capsule

Brood capsule: attached to germinal layer via the pedicle (stalk-like structure)
o Only has one layer (germinal layer)
o Protoscolex inside
o Protoscolex will eventually become another hydatid cyst
o Burst: protoscolex will become another hydatid cyst

Hydatid cyst ruptures: releases hydatid fluid
o Once it ruptures, all structures go down/settle down
o Ruptured cyst called hydatid sand

3 categories of hydatid cyst: unilocular, osseous, alveolar
o Unilocular: granulosus
o Alveolar and osseous: multilocularis
Cystic Echinococcosis, Hydatid Cyst seen, Cysticercosis of Visceral Organs

Affects liver and lungs

Cystic Echinococcosis: once cyst ruptures, disseminates to different vital organs (liver and lungs)

Simple cysts usually do not cause symptoms

Ruptured cysts can lead to
o Jaundice (obstruction in the liver)
o Eosinophilia
o Brain and renal involvement (due to dissemination of ruptured hydatid cyst)

Brain: increased intracranial pressure, Jacksonian epilepsy

Renal: pain, hematuria, kidney dysfunction, hydatid material in urine
o Triad: jaundice, fever, eosinophilia

Secondary infection of cyst may also occur
o Bacteria may enter cyst and lead to pyogenic abscess formation (patient has chills and fever)

Primary pathology of cyst: impairment of organs from mechanical pressure

Common in sheep grazing countries (Australia, New Zealand, Middle East, South America)

E. multilocularis: subarctic areas (Alaska, Canada)
102
N. Villanueva






E. vogeli: Central and South America
Diagnosis
Stool exam not performed (because it is found in the vital organs)
X-ray
Ultrasound, CT Scan
Surgery
Serology
o Bentonite Flocculation Test
o Casoni Intradermal Test (skin test)

Positive: wheal and flare reaction

Antigen from hydatid fluid injected to skin

Then you develop an immune reaction

Detects previous exposure to parasite
o ELISA
Treatment

Surgical resection (be careful kasi when it ruptures, can disseminate to other organs)

Albendazole

Praziquantel

PAIR (Puncture, Aspirate, Inject, Reaspirate)
o Inject scolicidal agent (95% Ethanol, hypertonic solutions, Hibitane)
Other Echinococcus species (uncommon because of sylvatic life cycle)

E. multilocularis
o FH: foxes
o IH: rodents (voles, lemmings, shrews, mice)
o Causes Alveolar Echinococcosis

Multilocular hydatid cyst produced (has many compartments)

Has no protoscolex inside

Produce gelly-like substance inside

Mistaken as carcinomas (cancer)

E. vogeli
o FH: bush dogs and dogs
o IH: rodents
o Multilocular hydatid cyst
o Causes polycystic echinococcosis (w/ E. oligarthrus)
MULTICEPS MULTICEPS
Life Cycle
Dog ingest
herbivores with
Coenurus
Humans/IH
ingest egg
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Coenurus develops to adult worm in
small intestine
Proglottids and eggs released
Larva develops
Larva can disseminate to different
vital organs
o Can go to brain
o Can go to eyes (can cause
blindness and ocular
infections)
Human releases Coenurus
103
N. Villanueva
Multiceps multiceps

Formerly known as Taenia multiceps

Gid Worm, Dog Sheep Tapeworm

FH: dogs and other canines (foxes, wolves)

Habitat: small intestine

Intermediate host: herbivores (sheep), man (accidental)

Infective stage: Coenurus

MOT: ingestion
Adult Worm

Scolex
o Pear shaped
o 2 rows of 22-30 hooks

Proglottids
o 1 lateral genital pore
Disease
Diagnosis
Treatment
Egg

Similar to Taenia (take note of
patient history before reporting)
Gid Disease, Coenurosis

Affects eyes and brain

Ocular infections, blindness, neurologic symptoms (seizures, changes in behavior)
Imaging
Surgery
104
N. Villanueva
LABORATORY DIAGNOSIS
Common specimens used to detect parasites include:
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Stool
Blood
Duodenal material
Sigmoidoscopy material (colon)
Perianal swab (cellulose acetate) preparation
CSF and other sterile fluids like peritoneal, pleural fluid,
and bronchial washings
Tissue and biopsy specimens
Sputum
Urine and genital specimens
Eye specimens
Mouth scrapings and nasal discharges
Skin snips
o
o
Fixation time: minimum of 30 minutes
If immunoassay for E. histolytica/dispar is requested,
fresh or frozen stools are required
Formalin
STOOL
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Most common specimen submitted
Different parasite stages can be detected
Container used: wide mouth, water tight, plastic container
with tight fitting lid
Other containers: Wax-lined carboard (0.24 L)
Stool containers should be placed in a plastic bag during
transport
Usually collect 3 specimens in a span of 10 days
o Done since parasite forms/stages are shed
intermittently and multiple collection increases
sensitivity of detection
o Up to 6 specimens collected in 14 days for detection
of amebiasis
o 1st 2 specimens: collected normally
o 3rd specimen: collected with the use of cathartic
Specimen should be properly labeled
Medications such as barium, bismuth, laxatives, and
mineral oil can interfere with parasite detection
o Patients taking these substances should defer stool
collection for a week after the last intake
o These substances can leave crystalline residues
o Antibiotics or antimalarials: delayed for 2 weeks
following therapy
Amount: 2-5 grams (walnut or thumb sized) of formed
stool
o Diarrheic stool: 5-6 tablespoons
As much as possible, specimen should be received and
examined by laboratory as soon as possible
o Liquid or diarrheic stools: within 30 minutes
o Semiformed stools: within 1 hour
o Formed stool: held for 1 day
o If immediate examination cannot be done, specimen
may be refrigerated or added with preservatives

Refrigeration is only temporary

Never keep stool samples in freezers or
incubators
Preservatives
o Fixatives: substances that preserve the morphology
and structure of parasite stages (also used to prevent
further development of parasites)
o Recommended fixative to stool ratio: 3:1
Merthiolate
Iodine
Formalin
(MIF)
Polyvinyl
Alcohol
(PVA)
Schaudinn’s
Sodium
Acetate
Formalin
Modified
Polyvinyl
Alcohol
Alternative
Single Vial
Systems
Fixatives
 All purpose fixative for helminthes and
protozoans
 5%: protozoans
 10%: helminthes
 can be used for direct examination (wet
mounts), concentration methods (FECT),
aqueous formalin for Giardia and
Cryptosporidium immunoassays,
sediments of stool fixed in formalin for
staining of intestinal coccidians (modified
acid fast) and microsporidia (modified
trichrome), and hot formalin (useful for
preserving helminth eggs)
 disadvantage: not used for making
permanent stained smears
 composed of merthiolate (thimerosal),
iodine, and formalin
 used for most parasite stages for field
studies
 usually used as a wet preparation
 usually combined with Schaudinn’s
Solution (which contains Mercuric
chloride)
 plastic powder which acts as an adhesive
 recommended for permanent stained
smears
 can also be used for concentration
methods
 usually incorporated in a two-vial system
 disadvantage: toxic
 for permanent stained smears from fresh
fecal specimens
 Gold standard
 Excellent for protozoan trophozoites and
cysts
 Softer fixative than mercuric chloride
 Alternative to PVA and Schaudinn
 Used for concentration techniques,
modified acid fast techniques, and
permanent stained smears
 Only requires a single vial
 Long shelf life
 Disadvantage: adhesive property is not
good, use of mayer’s albumin
 Alternative, safer than PVA
 Contains Copper sulfate or Zinc sulfate
 Used for concentration techniques and
permanent stained smears
 Morphology is not as good as PVA
 Zinc sulfate: provides better results
 Non-toxic fixatives
 Free of formalin and mercury
 For concentration techniques and
permanent stained smears
 For use of fecal immunoassays
105
MICROSCOPY: OVA AND PARASITE EXAMINATION
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Standard procedure performed in stool
Consists of a macroscopic and microscopic examination
MACROSCOPIC EXAMINATION
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Gross examination of stool specimens
Performed on unfixed or fresh stool specimens
Consistency or Form of Stool
o Can determine the potential parasite form (if cyst or
trophozoite)
o Can be hard, soft, mushy, loose, diarrheic, watery,
formed, or semi-formed
Color
o Brown: normal color, pigment responsible for brown
color is stercobilin/urobilin
o Purple, Red, Blue: due to medication
o Gray: may indicate bile duct obstruction
Gross Abnormalities
o May find adult worms, proglottids, pus, mucus, dark
colored blood, bright red blood

MICROSCOPIC EXAMINATION
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Visualization of parasite stages (also RBCs, WBCs,
macrophages, charcot-leyden crystals, fungi, plant cells,
pollen grains, plant fibers)
Direct Fecal Smear (Direct Wet Preparation)
o can use a Saline (NSS) or Iodine Mount
o Saline (NSS) Mount: can observe trophozoite
motility

Nair’s and Quensel’s Methylene Blue used to
observe nuclear details of trophozoite
o Iodine Mount: NSS + Lugol’s Iodine

Alternative to lugol’s: D’Antoni’s

Staining of cysts

Used for cysts only because iodine is toxic to
trophozoites
o Smears should be made thinly
o Standard slide: 1x3 inches
o Coverslip: 22x22 mm
o Direct preparation for NSS and Iodine mount is
prepared side by side on the slide
o Sealing can be done using paraffin and petroleum
jelly or nail polish
o Disadvantage: less sensitive, low diagnostic yield
Concentration Methods
o Parasites are aggregated into a small volume
o Removes fecal debris
o Detection of protozoan cysts, oocysts, helminth eggs,
and larva
o Trophozoites are not detected
o Principles

Sedimentation: recommended (has better
recovery)
N. Villanueva
Ex: Formalin Ether Concentration
Technique (FECT), AECT, Formalin Ethyl
Acetate Concentration Technique
(FEACT), MICT

Flotation: allows parasites to float

Ex: Zinc Sulfate Flotation (uses 33%
ZnSO4, specific gravity is 1.18 to 1.20),
Brine Flotation (supersaturated solution of
NaCl), Sheather’s Sugar Flotation

non-recovery of dense or heavy eggs
Permanent Stains
o the final procedure
o used for confirmation of the presence of a protozoan
cyst or trophozoites
o sample of choice: PVC fixed stool (with Schaudinn’s)
o Trichrome (Wheatley Modification)

Widely used, easy to prepare, has long shelf life

Usually with PVA

nuclear chromatin (peripheral and karyosome):
red-purple

background: blue-green

yeast: bright blue green or reddish
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cytoplasm: blue green, blue, blue-gray
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chromatoidal bar: bright to dark red
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charcot leyden crystals: bright red
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glycogen vacuole: colorless
o Ryan’s Trichome Stain: used for microsporidia
o Periodic Acid Schiff
o Chlorazol Black E
o Iron Hematoxylin

Time consuming

Has excellent morphology of intestinal
protozoans

Classical method

Stain should be fresh

Gives the best nuclear detail

Cytoplasm: blue-gray
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Nuclei and chromatoidal bar: dark blue or black
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RBC: black
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Charcot Leyden crystals: blue back
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Glycogen: colorless
o Specialized Stains

Modified acid fast stain

Modified iron hematoxylin (with carbolfuchsin)

 Ex: ECOFIX, TOTAL-FIX (Universal
Fixative)
OTHER TESTS FOR STOOL


Kato Thick: for qualitative examination of helminth eggs,
does not use a calibrated template
Kato-Katz: for
quantitative
examination of
helminth eggs,
amount of stool
is
standardized
with a template
o Wire mesh
is used
106
Green cellophane with glycerol is placed on top of
the slide

Glycerol: clearing agent, removes interfering
substances

Cellophane: to reduce eye strain
o Used to classify intensity or severity of disease
Stoll Egg Count: most widely used dilution egg counting
procedure
o 0.1 N NaOH and a stool displacement flask used
o Factor multiplied to 100 to determine egg per gram
Baermann Technique: for recovery of Strongyloides
stercoralis
o Funnel + gauze is used
Coproculture: uses a petri dish
Schistosomal Egg Hatching
Agar plate method
Harada-Mori Technique
o Uses a conical tube with water
o Filter paper with the stool is
placed inside
o Left standing for 7-10 days
o Used to identify rhabditiform or
filariform larvae
o Used for Hookworms and
Strongyloides
Culture Media for protozoans include
Diamond’s medium, Boeck and
Drbohlav’s Locke Egg Serum, and
Modified Thioglycolate medium
Stool screening done through rapid
methods
o Uses kits
o Ex: EIA, DFA
o
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OTHER INTESTINAL SPECIMENS
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Duodenal Material
o Used to detect parasites inhabiting the small intestine
o Collected by nasogastric intubation or the Enterotest
o Parasites observed includes Giardia,
Cryptosporidium, Isospora, Strongyloides, Fasciola,
Clonorchis
Sigmoidoscopy
o Detection of E. histolytica
o Done using biopsy specimens of the colon
Cellophane Tape Preparation
o Specimen of choice for Enterobius vermicularis

If stool is used to detect this, only a 5% chance
of recovery
o Can also be used for Taenia eggs
BLOOD
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For systemic or blood borne parasites
Wet Preparation: used to detect motility of filaria
o used to prepare a stained smear
o collect capillary blood (fingertip or earlobe)
o no anticoagulant is preferred
Preparation of Smears (Thin and Thick Smear)
o used to detect malaria
N. Villanueva
examined with the OIO
stained using Giemsa’s or Wright’s
other stains: Delafield Hematoxylin (for
demonstration of detailed structures of microfilaria)
o Thick is for quantification
o Thin is for species identification
o Examine under LPO to screen for presence of
microfilaria
Membrane Filtration
o Using a millipore filter (pore sizes depends on the
species to be detected)
o For microfilaria
o Uses EDTA or citrated blood diluted with TeepolSaline Solution (lysing solution)
o Stained with Giemsa
o Membrane filter has a 3-5 um diameter

5 um for Loa loa

4 um for W. bancrofti and other small species
o Examined initially under 10x
Knott Concentration Technique
o For concentrating microfilaria
o 1 ml of blood (EDTA) + 10 ml 2% formalin
o Centrifuge, then examine the sediment
o Stained with Giemsa (standard stain for blood
parasites)
Buffy coat slides
Cultures include NNN (Novy McNeal Nicolle Medium)
and Chang’s
o
o
o
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OTHER SPECIMENS
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CSF: for hemoflagellates, free-living ameba,
Parastrongylus, and Toxoplasma
Tissue specimens for Trichinella
Sputum for Paragonimus ova, migrating larva of Ascaris,
E. granulosus hooklets
o also used for Protozoa such as E. histolytica, C.
parvum, E. gingivalis, T. tenax
o first morning specimen is used (induction can be
done by using 10% sodium chloride or hydrogen
peroxide)
Urine: for Trichomonas and Schistosoma haematobium
Rectal biopsy for S. japonicum
Eye specimens for Acanthamoeba
Mouth scrapings for E. gingivalis and T. tenax
Nasal discharge for Naegleria
Skin snips for Onchocerca volvulus
RECENT ADVANCES IN DIAGNOSTIC PARASITOLOGY
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Microscopy: parasite concentration technique (like
FLOTAC) can be performed prior to microscopy
o Use of UV fluorescent microscope also a
recent advance
Immunodiagnosis: immunofluorescent assays, ELISA,
HA, immunoblotting
Molecular diagnosis
Rapid diagnostic tests
107