14. Protozoa - Parasitology Parasitology Parasite an...

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Parasitology Parasitology Parasite: an organism that lives on and at the expense of another organism 2 taxonomic groupings: 1) Protozoa - microscopic single-cell, eukaryotes 2) Helminths - macroscopic, multicellular worms with complex organ systems most protozoa and helminths are free-living disease producing species are usually obligate parasites Burden of Human Parasitic Infections Disease Estimated Population Involved Amebiasis 10%of world population Malaria population at risk population infected annual deaths 2 billion 270 million 1 - 2 million Hookworm 1 billion Ascariasis 1.5 billion Trichuriasis 800 million Strongyloidiasis 90 million Toxoplasmosis 40 - 50% of adults (Canada/USA) Giardiasis >200 million Protozoa 2 to > 100 µ m true membrane bound nucleus and cytoplasm most are facultative anaerobes many form a cyst wall for protection from environmental factors pathogenic and nonpathogenic strains Classes of Protozoa Class Organelles of Locomotion Method of Reproduction Examples Rhizopods (amebas) Pseudopods Binary fission Entamoeba histolytica Ciliates Cilia Binary fission Balantidium coli Flagellates Flagella Binary fission Giardia Lamblia Trichomonas vaginalis Sporozoa None Schizogony / Sporogony Plasmodium Toxoplasma gondii Entamoeba histolytica infects 10% of world’s population 3rd leading parasitic cause of death >90% of those infected shed the cyst form of the organism asymptomatically 1 - 2% of the Canadian population are seropositive infects the large intestine
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Epidemiology Humans are the only natural host Transmission - Ingestion of cyst in fecally contaminated water or food - Fecal-oral contact
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