Which o fthe human intestinal parasitic nematodes does not infest the small bowel?
Correct Answer: Trichuris trichiura
Description: Trichuris trichiura (whipworm) Whipworm infections are common worldwide with poor hygiene. Infection follows ingestion of eah or food contaminated with ova, which have become infective after lying for 3 weeks or more in moist soil. The adult worm is 3-5 cm long and has a coiled anterior end resembling a whip. Whipworms inhabit the caecum, lower ileum, appendix, colon and anal canal. There are usually no symptoms, but intense infections in children may cause persistent diarrhoea or rectal prolapse, and growth retardation. The diagnosis is readily made by identifying ova in faeces. Treatment is with mebendazole in doses of 100 mg twice daily or albendazole 400 mg daily for 3 days for patients with light infections, and for 5-7 days for those with heavy infections. Tissue-dwelling human nematodes Filarial worms are tissue-dwelling nematodes. The larval stages are inoculated by biting mosquitoes or flies, each specific to a paicular filarial species. The larvae develop into adult worms (2-50 cm long), which, after mating, produce millions of microfilariae (170-320 um long) that migrate in blood or skin. The life cycle is completed when the vector takes up microfilariae by biting humans. In the insect, ingested microfilariae develop into infective larvae for inoculation in humans, normally the only host. Disease is due to the host's immune response to the worms (both adult and microfilariae), paicularly dying worms, and its pattern and severity vary with the site and stage of each species . The worms are long-lived: microfilariae survive 2-3 years and adult worms 10-15 years. The infections are chronic and worst in individuals constantly reinfected. Ref Harrison20th edition pg 1023
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