(roundworm) Gnathostoma spinigerum and Gnathostoma hispidum,
which infects vertebrate animals. Human gnathostomiasis is due to
migrating immature worms.
In the natural
definitive host (pigs, cats, dogs, wild animals) the adult worms reside
in a tumor which they induce in the gastric wall. They deposit eggs
that are unembryonated when passed in the feces
Eggs become embryonated in water, and eggs release first-stage larvae
If ingested by a small crustacean (Cyclops, first intermediate
host), the first-stage larvae develop into second-stage larvae
Following ingestion of the Cyclops by a fish, frog, or snake
(second intermediate host), the second-stage larvae migrate into the
flesh and develop into third-stage larvae
When the second intermediate host is ingested by a definitive host, the
third-stage larvae develop into adult parasites in the stomach wall
Alternatively, the second intermediate host may be ingested by the
paratenic host (animals such as birds, snakes, and frogs) in which the
third-stage larvae do not develop further but remain infective to the
Humans become infected by eating undercooked fish or poultry containing
third-stage larvae, or reportedly by drinking water containing infective
second-stage larvae in Cyclops
Thailand and Japan; recently emerged as an important human parasite in
manifestations in human gnathostomiasis are caused by migration of the
immature worms (L3s). Migration in the subcutaneous tissues causes
intermittent, migratory, painful, pruritic swellings (cutaneous larva
migrans). Migration to other tissues (visceral larva migrans), can
result in cough, hematuria, and ocular involvement, with the most
serious manifestations eosinophilic meningitis with myeloencephalitis.
High eosinophilia is present.
identification of the worm is both diagnostic and therapeutic.
or treatment with albendazole* or ivermectin* is recommended.
* This drug is
approved by the FDA, but considered investigational for this purpose.