15. Helminths - Helminths Helminths (Nematodes) Worm...

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Helminths (Nematodes) Helminths • Worm infections - major groups include: i) Nematodes (roundworms) ii) Trematodes (flukes) iii) Cestodes (tapeworms) • Macroparasites - 1 cm to 10 cm in length • Multicellular complex organisms with differentiated organ systems Major Helminth Infection of Humans Group Organism Mode of transmision to humans Nematodes Enterobius vermicularis Ingestion of eggs Trichuris trichiura Ingestion of eggs Ascaris lumbricoides Ingestion of eggs Ancylostoma duodenale Skin penetration by larvae Strongyloides stercoralis Larva penetrate skin or colon Trichinella spiralis Ingestion of muscle larvae Trematodes Schistosoma spp. Skin penetration by cercariae Cestodes Echinococcus granulosus Ingestion of eggs Taenia saginata Ingestion of cysticerci in beef Taenia solium Ingestion of cysticerci in pork Ingestion of eggs Diphyllobrothrium latum Ingestion of cysts in freshwater fish Life Cycle • Infection in humans initiated by: i) ingestion of parasite eggs or larvae ii) penetration of intact skin by larvae iii) bite of insect vector • In humans, worms mature and differentiate into male and female sexual reproduction produce eggs and larvae that are excreted • Most unable to multiply within human host
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15. Helminths - Helminths Helminths (Nematodes) Worm...

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