The eggs of five tongue worm species are infective to humans, and in four of these species (Armillifer grandis, A. armil-latus, A. moniliformis, and A. agkistrodontis), humans are merely an accidental intermediate host. Nearly always, nymphal infections are acquired when eggs in undercooked meat, derived from tongue worm-infected snakes, are consumed. The epidemiology of the remaining species, Linguatula serrata from the nasal sinuses of dogs, is complicated, because both eggs and infective larvae can become established in humans. Ingested eggs hatch to produce infective nymphs. In contrast, if ingested in contaminated offal from sheep or goats, nymphs attempt to migrate from the stomach to the nasal passages, producing acute symptoms of nasopharyngeal linguatulosis.
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