Illustration of a guinea worm (Dracunculus medinensis) emerging from an infected foot. The white thread-like worm is seen at centre; the female worm is a human parasite and may measure more than 1 metre long. Guinea worm disease, known as dracunculiasis, occurs in the tropics. Infection is through drinking water containing the water flea which harbours larvae of the worm. The larvae mature in body tissues. Nausea, vomiting and diarrhoea often develop. Once adult, the female worms blister the skin to escape from their host. A traditional remedy is to remove the worm by winding it on a small stick.