Human gnathostomiasis is caused by several species of parasitic worms (nematodes) in the genus Gnathostoma. The disease is found and is most commonly diagnosed in Southeast Asia, though it has also been found elsewhere in Asia, in South and Central America, and in some areas of Africa. People become infected primarily by eating undercooked or raw freshwater fish, eels, frogs, birds, and reptiles. The most common manifestations of the infection in humans are migratory swellings under the skin and increased levels of eosinophils in the blood. Rarely, the parasite can enter other tissues such as the liver, and the eye, resulting in vision loss or blindness, and the nerves, spinal cord, or brain, resulting in nerve pain, paralysis, coma and death.

Image: Left/Right: Third-stage larva of Gnathostoma spinigerum, head and whole larva respectively. Center: Scanning electron micrograph of a Gnathostoma spinigerum female worm's head bulb. Credit: DPDx