Transmission
Gnathostomiasis is transmitted by the ingestion of raw or insufficiently cooked definitive hosts such as fresh water fish, 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. Hosts
Intermediate host
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. Definitive host
The definitive hosts for gnathostomiasis include cats, dogs, tigers, leopards, lions, mink, opossums, raccoons, poultry, frogs, freshwater fish, snakes or birds. Incubation period
The incubation period for gnathostomiasis is 3–4 weeks when the larvae begin to migrate through the subcutaneous tissue of the body. Morphology
The adult parasite is reddish-brown in color and has a globular cephalic dome that is separated from the rest of the body by constriction. The posterior portion of the nematode is smooth while the anterior half is covered with fine leaf-like spines. The head is round and contains 4 to 8 transverse rows of hooklets that are protected by a pair of fleshy lips . The males are shorter than the females, 11–25 mm (0.43–0.98 in) compared to 25–54 mm (0.98–2.13 in) respectively. Eggs are oval and have a mucoid plug at one end.
Gnathostomiasis (also known as larva migrans profundus: 436 ) is the human infection caused by the nematode (roundworm) Gnathostoma spinigerum and/or Gnathostoma hispidum, which infects vertebrates. Symptoms and signs
A few days after ingestion epigastric pain, fever, vomiting, and loss of appetite resulting from migration of larvae through intestinal wall to the abdominal cavity will appear in the patient. Migration in the subcutaneous tissues (under the skin) causes intermittent, migratory, painful, pruritic swellings (cutaneous larva migrans). Patches of edema appear after the above symptoms clear and are usually found on the abdomen. These lesions vary in size and can be accompanied by pruritus (itchy anus), rash, and stabbing pain. Swellings may last for 1 to 4 weeks in a given area and then reappear in a different location. Migration to other tissues (visceral larva migrans), can result in cough, hematuria (blood in urine), ocular (eye) involvement, meningitis, encephalitis and eosinophilia. Eosinophilic myeloencephalitis may also result from invasion of the central nervous system by the larvae. Causes
Human gnathostomiasis is infection by the migrating third-stage larvae of any of five species of Gnathostoma, which is type of worm (more specifically a type of nematode). 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.