Learn about a disease caused by a parasitic infection from a three-foot-long worm, in this episode of Gross Science from NOVA. Dracunculiasis is caused by the Guinea worm—a nematode that has historically been a major problem in Asia and Africa. People can be infected when they drink water contaminated with water fleas, which house guinea worm larvae. Over the course of a year, the matured female Guinea worm burrows through the body of its human host and forms a blister full of larvae in the foot, which bursts when exposed to water. Filtering drinking water, and preventing the contamination of water, can stop the spread of the disease. In the mid-eighties, there were over three million cases of Guinea worm disease; however, in 2014 there were only 126 cases. In the next few years, Guinea worm disease will probably become the first parasitic disease to be eradicated. This resource is part of the NOVA: Gross Science Collection.