75 下列何種人體寄生蟲具有腸道自體感染（intestinal autoinfection）的現象？

蛔蟲（Ascaris lumbricoides） 糞小桿線蟲（Strongyloides stercoralis）

美洲鉤蟲（Necator americanus） 鞭蟲（Trichuris trichiura）

answer: S. stercoralis

Autoinfection is the infection of a primary host with a parasite, particularly a helminth, in such a way that the complete life cycle of the parasite happens in a single organism, without the involvement of another host. Therefore, the primary host is at the same time the secondary host of the parasite. Some of the organisms where autoinfection occurs are Strongyloides stercoralis, Enterobius vermicularis, Taenia solium, and Hymenolepis nana.

Strongyloidiasis for example involves premature transformation of noninfective larvae in infective larvae, which can then penetrate the intestinal mucosa (internal autoinfection) or the skin of the perineal area (external autoinfection). Infection can be maintained by repeated migratory cycles for the remainder of the person's life.

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