Pro

1. unit 7 parasitology
General Introduction
Key terms
 medical parasitology is the science that deals with the medically
important parasites & their interaction with human host and
disease causation.
 parasite is an organism that is entirely dependent on another
organism, referred to as its host, for all or part of its life cycle
and metabolic requirements.
 Eukaryote: a cell with a well-defined chromosome in a
membrane-bound nucleus. E.g. All parasites
 Protozoa: unicellular organisms, e.g. Plasmodium (malaria)
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2. Cont’d…
 Metazoa: Multicellular organisms, e.g. helminths and
arthropods
 Endoparasite: a parasite that lives within another living
organism e.g. malaria, Giardia
 Ectoparasite: a parasite that lives on the external surface of
another living organism. e.g. lice, ticks
 Host: an organism in/on which the parasite lives and causes
harm
 Definitive host: the organism in which the adult or sexually
mature stage of the parasite lives
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3. Cont’d…
 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
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4. Classification of the parasite
 based on the anatomical position of the host
Intestinal
Hemoparasite
Tissue parasite
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5. Types of hosts
 Definitive host – a host that harbors a parasite in the adult
stage or where the parasite undergoes a sexual method of
reproduction.
 Intermediate host-harbors the larval stages of the parasite or
an asexual cycle of development takes place.
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6. o What differentiates parasites from hosts?
 Size
 Generation rate
 Life spans
 Abundance
 Dependence
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7. Five kingdoms of life(monera, protists, fungi, plants and animals)
o Kingdom: protists
 Subkingdom:Protozoa
 Phylum Sarcomastigophora
 Phylum Apicomplexa
 Phylum Ciliophora
o Kingdom: Anemalia
 Subkingdom: metazoa
 Phylum Nemathelminthes
 Phylum Platyhelminthes
Classification of medical importance parasites
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8. MEDICAL PROTOZOLOGY
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9.  Most Intestinal protozoa parasites have two stages:
 Cyst
 non vegetative, dormant, inactive form and resistant
unfavorable env’tal conditions
 it is the infective/diagnostic stage.
 Trophozoite
 Vegetative, motile, metabolically active & invasive stage of a parasite.
 It is not infective/diagnostic stage
From an ecological point of view, protozoa - divided into
 free-living forms
 symbiotic forms
Protozoa con…
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10. Locomotion/motility
protozoa organ of locomotion important human
pathogens
1.Amoeba Pseudopodia /false foot E. histolytica
2. Mastigophora
(Flagellates)
Flagella Trypanosomes
Leishmania
Trichomonas
Giardia
3. Sporozoa None, exhibit a slight
Amoeboid movement
Plasmodium.Spp
4. Ciliates Cilia Balantidium coli
Different protozoan have different means of locomotive organs
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