Gnathostomiasis

Gnathostomiasis, also known as larva migrans profundus, is the human infection caused by the nematode Gnathostoma spinigerum and/or Gnathostoma hispidum, which infects vertebrates.

A few days after ingestion epigastric pain, fever, vomiting, and loss of appetite resulting from the migration of larvae through the intestinal wall to the abdominal cavity will appear in the patient. Migration of parasites in the subcutaneous tissues causing intermittent, migratory, painful, pruritic swellings is known as cutaneous larva migrans. Patches of edema appear after initial symptoms clear and are usually found on the abdomen. These lesions vary in size and can be accompanied by pruritus, rash, and stabbing pain. Swellings may last 1 to 4 weeks in a given area and reappear in a different location. Migration to other tissues causes visceral larva migrans and can result in cough, hematuria, ocular involvement, meningitis, encephalitis and eosinophilia. Eosinophilic myeloencephalitis may also result from invasion of the central nervous system by the larvae.

Human gnathostomiasis is an infection by the migrating third-stage larvae of any of five species of Gnathostoma. The most common cause in Asia is G. spinigerum, and the most common cause in the Americas is G. binucleatum. G. hispidium and G. doloresi occur in East and Southeast Asia; the former has also been found in Eastern Europe. G. nipponicum occurs only in Japan and China. There is one unconfirmed report of G. malaysiae causing disease in humans.

Gnathostomiasis is transmitted by the ingestion of third-stage larvae from raw or insufficiently cooked second intermediate or paratenic hosts such as freshwater fish, snakes, poultry, or frogs.

In Thailand and Vietnam, the most common cause appears to be consumption of undercooked Asian swamp eels (Monopterus albus, also called Fluta alba) which transmit G. spinigerum. Monopterus albus is an invasive species in North America, but no Gnathostoma infections in humans have yet been conclusively identified in the US.

It is unclear if humans can be infected from drinking water contaminated with infected copepods.

The primary intermediate host is the minute crustaceans of the genus Cyclops. These crustaceans are then ingested by a second intermediate host, such as frogs and freshwater fish. Paratenic hosts are usually animals that prey on second intermediate hosts, such as snakes and birds.

The definitive hosts for gnathostomiasis include omnivorous or carnivorous mammals such as cats, dogs, tigers, leopards, lions, mink, opossums or raccoons. Humans are accidental hosts, not definitive hosts.