Gnathostomiasis (Gnathostoma Infection)
Gnathostomiasis is an infectious disease caused by the nematodes Gnathostoma shispidum and the Gnathostoma spinigerum. These roundworms impact various vertebrate animals and the disease is caused in humans by immature worms in migration. The parasite can be found in Japan, Thailand, other parts of Asia, and more recently in Mexico.
The nematodes inhabit a tumor within the gastric wall of the definitive host, usually a pig, dog, or a cat. There, eggs are deposited that pass through with excrement. The eggs are embryonated in water and release larvae. The larvae are consumed by small crustaceans that act as intermediate hosts. The larvae develop into second-stage form and are then consumed by a second intermediate host such as a snake, fish, or a frog. Inside this host, the larvae mature further. The second intermediate host is then consumed by a definitive host, inside which the larvae mature into adulthood within the stomach wall.
It is possible that the second intermediate host is consumed by a paratenic host, in which case the larvae do not mature into adulthood but still remain infectious for a definitive host to come along. Human infection occurs from consumption of undercooked or raw hosts, or possibly from consumption of larvae contaminated water.
Symptoms of Gnathostomiasis in humans manifest when immature roundworms are migrating in the subcutaneous tissues. This can cause painful and pruritic swellings known as cutaneous larva migrans. Visceral larva migrans can occur as the immature worms move to other tissues, causing coughing, ocular involvement, haematuria. Severe symptoms could be the presence of high eosinophilia, and eosinophilic meningitis with myeloencephalitis.
Diagnosis of Gnathostomiasis requires microscopy to identify the roundworm. Treatment of Gnathostomiasis can require surgery to remove the roundworms. Treatment with ivermectin or albendazole is another option. Surgery and medication may be used in combination.