Human gnathostomiasis.

Two patients became infested with Gnathostoma nipponicum after eating raw loach-fish they had caught in a rice field in central Japan. A fragment of Gnathostoma was found in a biopsy from one of them. The sera of both patients reacted with Gnathostoma antigen using indirect immunofluorescence. Scanning electron microscopy was performed on blocks of the paraffin-embedded parasite sample and the viscera of a fish from the same rice field. The risk of eating raw freshwater fish is discussed.