Gnathostoma spinigerum

Description

This species grows to a length of up to 54 mm, with females longer and wider on average than males.

Life history

Gnathostoma spinigerum has a multi-host life history. The eggs hatch in fresh water and the larvae are eaten by copepods of the order Cyclopoida. The copepods are in turn eaten by second intermediate hosts (fish and amphibians), which may be consumed in turn by paratenic or transport hosts (reptiles and birds). Eventually, the larvae end up in the stomachs of carnivores, usually cats and dogs. Humans may acquire the nematode larvae by consuming raw or undercooked meat from any of the intermediate or paratenic hosts. In carnivores, the larvae embed in the stomach wall and develop into adults. Embryos develop in eggs which reach fresh water. In humans, the larvae commonly migrate to the skin, but may also move into various internal tissues. Larvae in humans may develop into immature adults, but never reach reproductive maturity.

Geographic range

The first described case of gnathostomiasis was in a young tiger that died in the London Zoo in 1835.

Although Gnathostoma spinigerum are considered endemic to Thailand, they are also found in many other countries of Southeast Asia. These nematode parasites have also been reported to be found in Japan and Australia. However, the incidence of infection is rarer outside the Asian continent.

Habitat

Gnathostoma spinigerum normally could be found in wet tropical environments. Larvae can infect many classes of animals. Canine and feline species, and possibly pigs, are determined as the definitive hosts. In Japan, freshwater fishes, Ophicephalus argus and O. tadianus, are the most important vectors of human gnathostomiasis. In addition to freshwater fishes, domestic duck, Anas platyrhynchus and the domestic chicken Gallus gallus domesticus carry the parasite in Thailand. In Japan, natural hosts of G. spinigerum include 32 species of animals.

Prevention of gnathostomiasis

In a study done in Thailand, researchers have proposed a method of prevention of gnathostomiasis. It states that humans can become infected via eating fresh water fish. For example, a popular dish serving fermented fresh water fish is popular among the women of Thailand, which may explain their higher incidence of the infection. In order to avoid or kill the infective larva living in fish muscle, one must boil the fish first for a minimum of five minutes, placed in a solution of vinegar and 4% acetic acid for a period of 5.5 hours, or just to avoid raw or undercooked fish, always being sure to cook fresh water fish thoroughly.

Treatment of gnathostomiasis

Laboratory testing on mice treated once or twice daily with albendazole were shown to have a significant reduction in worm count when compared to the untreated mice group. The effective dosage at which albendazole has been shown effective is 90 mg/kg twice a day for 21 straight days. On the other hand, there are other antihelminthic drugs available such as bithionol, thiabendazole, metronidazole, and others, that did not reveal any significant therapeutic effects in experimental G. spinigerum infections.

References

References

1. {{GBIF
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