Parasitology
What are parasites and
what do they cause?
Parasitology
 Protozoan
 Single cell organism belonging to Kingdom
Protista.
 Of 20,000 species only a few cause disease
 Helminth
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Platyhelminth (Flatworm)
Aschelminth (Roundworm)
Multicellular, most free-living
A few are parasites
Protozoan: Motility
 Sarcodina (amoeba) - move by extending
projections, pseudopods, from cytoplasm
 Mastigophora (flagella) - whip-like movement
that pull cell through medium
 Ciliaphora (cilia) - propel cell through medium,
similar but shorter than bacteria flagella
 Apicomplexia (sporozoa) – no observed
independent movement
Biology of Protozoans
 Aerobic heterotrophs, areas with water
 Reproduction, asexual or sexual
 Encystment – under adverse conditions, produce
protective capsule cyst
 Survive without food, water, oxygen; unsuitable
temperature or chemical conditions
 For parasites allows survival outside host
Medically Important
Protozoan
 Intestinal Amebae
 Entamoeba
 Intestinal & Urogenital Flagellates
 Giardia, Trichomonas
 Ciliates
 Balantidium
 Sporozoa
 Plasmodium
Amebae: Entamoeba histolytica
 Amebic dysentery (diarrhea with blood and
mucous)
 Bores through intestinal wall to cause
ulcers in intestine and liver
 Two stages – trophozoite (motile) and cyst
 Transmitted from human to human via cyst
passed in feces and ingested by next host
 Diagnosis – trophozoite or cyst in feces
Ciliates: Balantidium coli
 Dysentery - severe, rare type of
dysentery
 Two stage life cycle – trophozoite and cyst
 Humans acquire by ingestion of cysts
passed in feces
 Diagnosis - cyst or trophozoite in feces
Flagellates: Giardia lamblia
 Traveler’s diarrhea, hiker’s diarrhea
 Acute or chronic enteritis, common in
children
 Found in small intestine
 By ingestion of cyst passed in feces
 Diagnosis by finding trophozoite or cyst in
feces
Flagellates: Trichomonas vaginalis
 Vaginitis
 Only trophozoite stage, must be
quickly transferred from host to host
 Inhabits female vaginal tract and male
urinary tract
 Transmitted as STD, contaminated
toilet facilities or towels
Sporozoa: Plasmodium
 Malaria, complex life cycle
 Mature forms are obligate intracellular
parasites
 Anopheles mosquito bite and inject
sporozoite (infective stage for humans)
 Exoerythrocytic cycle: Sporozoite goes to
liver, undergo schizogony, produces
merozoites
 Erythrocytic cycle: Merozoites released,
either reinfect new liver cells or infect
RBC
Erythrocytic Life Cycle
 In RBC, transforms into
trophozoite (a ring
consisting of nucleus and
cytoplasm)
 Ring stage enlarges and
divides repeatedly to form
many merozoites
 RBCs rupture and
merozoites released
 Causes fever and chills (a
febrile paroxysm)
 Most merozoites reinfect
new RBCs and undergo a
new cycle of asexual
Sexual Cycle In Mosquito
 Some merozoites develop into
male and female sexual forms
(gametocytes)
 Gametocytes picked up by
mosquito when feeding on
infected host, enter intestine to
begin sexual cycle
 Male and female gametocytes
unite into zygote, forms cyst
intestine wall
 Cell division occurs, asexual
sporozoites formed
 Cyst ruptures, sporozoites
migrate to salivary glands of
mosquito from where injected
into new human host
Helminths
 Reproductive systems of parasitic
species highly developed
 Life cycle – may be extremely
complex and many different host
 Definitive host – harbors adult,
sexually mature helminth
 Intermediate host – harbors larval or
developmental stage
Platyhelminth: Flatworm
 Dorsoventrally flattened and either
lack or incomplete digestive system
 Trematodes (flukes)
 Intestinal – Fasciola
 Blood – Schistosoma
 Cestodes (tapeworms)
 Intestinal -Taenia
Blood Fluke: Schistosoma
 Schistosomiasis
 Adults live in mesenteric and pelvic veins of
humans
 Cercaria are not ingested but burrow through
skin of human host and enter circulatory
system
 Fresh water snails as intermediate host
 Diagnosis by finding eggs in urine and feces
Intestinal Tapeworms
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Head (scolex) has suckers, hooks; attach intestinal mucosa
Lack digestive system, absorb food through cuticle
Body of segments (proglottids) continually produced
Proglottid contains both male and female organs
Gravid proglottid furthest from scolex filled with eggs
Tapeworms: Taenia
 Humans as definitive host –
 Taenia saginata (beef tapeworm)
 Tania solium (pork tapeworm).
 Adult Taenia found in humans
 Mature proglottids with eggs are
released in feces (diagnosis)
 Upon ingestion by cattle or pigs, larvae
hatch and encyst in muscles as
cysticercus
 Then ingested by humans eating
undercooked beef or pork
Aschelminths – Roundworms
 Complete digestive system
 Most dioecious (male reporductive organs in one
and female in another)
 Class Nematode has human parasites
 No complicated life cycles
 Eggs infective for humans:
 Enterobius
 Ascaris
 Larvae infective for humans:
 Necator
Pinworm: Enterobius vermicularis
 Spends entire life in humans
 Adult worms in large
intestine
 Female migrates to anus to
deposit eggs, causes itching,
most common symptom
 Eggs ingested by host or
another human (commonly
transmitted in young
children by poor hygiene)
 Diagnosis – pick up using
sticky tape method and
observe by microscopy
Roundworms: Ascaris lumbricoides
 Large – 30cm. in length
 Adults live in small intestine of humans,
pigs, horses
 Eggs excreted in feces, survive in soil
 Infection occurs by ingesting eggs
 Diagnosis by finding eggs in feces
Hookworm: Necator americanus
 Adults live in small
intestine, eggs excreted
with feces
 Hatch in soil, larva
enter new host by
penetrating skin
 Go to blood and lungs,
swallowed and get to
small intestine to
mature into adult
 Diagnosis by finding
eggs in feces
 To prevent infection –
wear shoes
MICR 301
Final Exam (200 pts.)
 Tuesday, Dec. 6, 2011
 8:00 – 10:30am
 Lecture, Reading, Key Terms, Learning
Assessment Questions, Five Case Study
 Virus, Bacteria, Fungi, Parasite Lectures
 Part I (~65%): Mechanism of Pathogenesis
thru Parasites
 Part II (~35%): Introduction thru
Specific Host Defense
 Objective (M.C., Terms, T/F), Short Essay
QUESTIONS???
ALL I REALLY NEED
TO KNOW
ALL I REALLY NEED TO
KNOW I LEARNED IN
KINDERGARTEN
• Robert Fulghum
ALL I REALLY
NEED TO KNOW
• about how to live and what to do and
how to be I learned in kindergarten.
• Wisdom was not at the top of the
graduate-school mountain, but there
in the sandpile at Sunday School.
These are the things I
learned:
•
•
•
•
Share everything.
Play fair.
Don’t hit people.
Put things back where you found
them.
• Clean up your own mess.
• Don’t take things that aren’t yours.
• Say you’re sorry when you hurt
somebody.
• Wash your hands before you eat.
• Flush.
• Warm cookies and cold milk are good
for you.
• Live a balanced life – learn some and
think some and draw and paint and
sing and dance and play and work
every day some.
• Take a nap every
afternoon.
• When you go out
into the world,
watch out for
traffic, hold
hands, and stick
together.
• Be aware of wonder.
• Remember the little seed in
the Styrofoam cup:
• The roots go down and the
plant goes up and nobody
really knows how or why,
but we are all like that.
• Goldfish and hamsters and white
mice and even the little seed in the
Styrofoam cup – they all die.
• So do we.
• And then remember the Dick-andJane books and the first word you
learned – the biggest word of all –
•
LOOK.
LOOK
• Fulghum, Robert.
• 1988. All I Really Need To Know I Learned
In Kindergarten: Uncommon Thoughts On
Common Things. New York: Villard Books.
• 2003. 15th Anniversary Edition. All I Really
Need To Know I Learned In Kindergarten:
Reconsidered, Revised & Expanded, With
Twenty-Five New Essays. New York:
Ballantine Books.
ALOHA
Kauai, Hawaii