Prof.Dr. Hamdy El-Wakil
Professor in Parasitology.
Vice Dean in faculty of physiotherapy
pharos University
2013M-1434H
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Human parasitology is the study of
those organisms which parasitize
humans. According to the very broad
definition of parasitology, parasites
should include the viruses, bacteria,
fungi, protozoa (protista) and metazoa
(multi-celled organisms) which infect
their host species. However, for
historical reasons the first three have
been incorporated into the discipline
of Microbiology.
After completing this course, you should be able to:
 Discuss how important parasites can be classified according
to kingdom and phylum
 State the meaning of commonly-used terms
 Describe how parasitic infections affect communities in poor
countries and that knowledge of their life cycle is necessary
for effective prevention and control
 Discuss the epidemiology, basic life cycle, clinical
presentation, management and control of some important
parasitic infections
Note: This course will contain many unfamiliar terms. You are
NOT expected to remember the classifications and names of
all of the different parasite species. The emphasis is on
understanding basic concepts and being able to illustrate
these with some important examples.
After completing this course, you will associated a quiz to
assess your learning.
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Parasite
Plasmodium
Diseases
malaria
Soil transmitted helminthes:
•
Roundworm (Ascaris)
•
•
•
Whipworm (Trichuris)
Hookworm
(Ancylostoma and
Necator)
No. people infected
Deaths/yr
273 million
1.12 million
2 billion
200,000
Pnemonitis, intestinal
obstruction
Bloody diarrhoea, rectal
prolapse
Coughing, wheezing,
abdominal pain and
anaemia
Schistosoma
Renal tract and intestinal
disease
200 million
15,000
Filariae
Lymphatic filariasis and
elephantiasis
120 million
Not fatal but 40 million
disfigured or
incapacitated
Trypanasoma cruzi
Chagas disease
(cardiovascular)
13 million
14,000
African trypanosomes
African sleeping sickness
0.3 – 0.5 million
48,000
Leishamania
Cutaneous,
mucocutaneous and
visceral leishmaniasis
12 million; 2 million new
cases/yr
50,000
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Classification of parasites and vectors
Animal Kingdom
Sub-Kingdom
(Protozoa) Unicellular
parasites=kingdom
Sub-Kingdom
(Metazoa)
Multicellular animals
Protista
Phylum Helminthes : Phylum Arthropods :Phylum
Molluscs
Subphylum: Sarcodina e.g. Amoeba
Phylum: Sarcomastigophora:
Subphylum:Mastigophora e.g. Trypansoma
Phylum: Ciliphora: Class: Ciliates e.g. Balantidium coli
Phylum: Apicomplexa: Class: Sporozoa e.g. Plasmodium Sp.
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Sub
kingdom
=kingdom
Protista
Unicellular
Protozoa
Phylum
Sarcomastigophora
further divided into
Sub-phylum
Sarcodina-- -
Genusexamples
Speciesexamples
Entamoeba
E. histolytica
Giardia
G. lamblia
Plasmodium
P. falciparum,
P. vivax,
P. malariae,
P. ovale
Balantidium
B. coli
Enterocytozoa
E. bieneusi
move by
pseudopodia
Mastigophora
move by flagella
Apicomplexa
no organelle of
locomotion
Ciliophora
move by cillia
Microspora
Spore-forming
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Sub
kingdom
Metazoa
Multicellular
animals
Phylum
Class
Ascaris (roundworm)
Trichuris (whipworm)
Ancylostoma (hookworm)
Necator (hookworm)
Enterobius (pinworm or
threadworm)
Strongyloides
Nematodes
Round worms; appear round in
cross section, they have body
cavities, a straight alimentary
canal and an anus
Platyhelminthes or
Plathelminthes
Flat worms; dorsoventrally
flattened, no body cavity and, if
present, the alimentary canal is
blind ending
Genus – examples
Cestodes
Taenia (tapeworm)
Adult tapeworms are found in
the intestine of their host
They have a head (scolex) with
sucking organs, a segmented
body but no alimentary canal
Each body segment is
hermaphrodite
Trematodes
Non-segmented, usually leafshaped, with two suckers but no
distinct head
They have an alimentary canal
and are usually hermaphrodite
and leaf shaped
Schistosomes are the
exception. They are thread-like,
and have separate sexes
Fasciolopsis (liver fluke)
Schistosoma (not leaf shaped!)
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Although parasitic infections occur globally, the majority
occur in tropical regions, where there is poverty, poor
sanitation and personal hygiene
Often entire communities may be infected with multiple,
different organisms which remain untreated because
treatment is neither accessible nor affordable
Effective prevention and control requires "mass intervention
strategies” and intense community education. Examples
include:
◦ General improved sanitation: pit latrines, fresh water wells,
piped water
◦ Vector control: insecticide impregnated bed nets, spraying
of houses with residual insecticides, drainage, landfill
◦ Mass screening and drug administration programmes which
may need to be repeated at regular intervals
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Parasite transmission
Indirect
(with intermediate hosts)
(1) Requiring (2) Requiring
one
Two
intermediate intermediate
host
hosts
Wuchereria bancrofti
•
H. Hetrophyes
 Onchocerca volvulus
 Dracunculus medinensis
 Trichuris trichiura

Fasciolopsis buski Dipylidium caninum

(1)Taking a
period to
become
infectious
Ascaris lumbricoides
Clonorchis sp.
Paragonimus
westermani
(without intermediate host)
 Loa loa


Direct
 Ancylostoma duodenale
 Taenia spp
 Necator americana
. Schistoma spp
 Strongyloides stercoralis
. Leishmania spp.
Diphyllobothrium
Fasciola spp.
L.
(2) Immediately
infective
 Entamoeba histolytica
Giardia lamblia
 Balantidium coli
 Trichomonas sp
. Hymenolepis nana
 Enterobius vermicularis
 Sarcoptes scabiei
 Pediculus huminus
 Phthirus pubis
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Eukaryote: a cell with a well-defined chromosome in a
membrane-bound nucleus. All parasitic organisms are
eukaryotes
Prokaryotic organelles
Prokaryotes are not as structurally complex as eukaryotes, and
were once thought not to have any internal structures enclosed
by lipid membranes.

Protozoa: unicellular organisms, e.g. Plasmodium (malaria)

Metazoa: Multicellular organisms, e.g. helminths (worms) and
arthropods (ticks, lice)

An endoparasite: “a parasite that lives within another living
organism” – e.g. malaria, Giardia

An ectoparasite: “a parasite that lives on the external surface of
another living organism” – e.g. lice, ticks
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Definitive host: “the organism in which the adult or sexually mature
stage of the parasite lives”

Intermediate host: “the organism in which the parasite lives during a
period of its development only”

Zoonosis: “a parasitic disease in which an animal is normally the
host - but which also infects man”

Vector: “a living carrier (e.g.an arthropod) that transports a
pathogenic organism from an infected to a non-infected host”. A
typical example is the female Anopheles mosquito that transmits
malaria
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Parasitology :
Is the science which deals with parasitism, in other
hand, it studies the host parasite relationships.
Medical parasitology: Deals with the study of
parasites of animal origin, belonging to the animal
kingdom, and affecting man, the disease they
produce, the various methods of their diagnosis,
their treatment and finally prevention and control.
Parasite :
Any organism is considered as a parasite when it
lives either on or in another organism to obtain food
and shelter without compensation.
Definitions: What is ….?
Host :
Is the living organism which harbours the parasites.
Habitat :
Is the site in the host where the parasite lives.
Parasites vary according to their biological habits.
Commensal :
If the parasite derives benefit from its host without harming it, it
becomes, known as a commensal.
Symbiosis:
If on the other hand the association between them is so that one
cannot live without the help of the other, then this relationship
becomes known as symbiosis, but usually a parasite causes injury to
its host.
Endemic parasite:
Maintains a relatively moderate steady level of parasitism in man in a
certain area. Also, a parasite is called hyperendemic when its prevalence
or incidence is relatively high.
Epidemic parasite:
When these exist a sharp rise in the prevalence of infection or
infestation culminating in an intense outbreak of the disease.
Students will prepare an assignment in one of
the parasites that have been taken in your
lecture.
Three points should be covered in his/her
assignment:
1. A real infective stage photo of the parasite.
2. Diagnostic stage photo
3. Parasite scientific name, illness or the
disease name ,Importance and life cycle.
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