Dracunculiasis, also called Guinea-worm disease, is a parasitic infection by the Guinea worm (Dracunculus medinensis). A person becomes infected by drinking water contaminated with Guinea-worm larvae that reside inside copepods (a type of small crustacean). Stomach acid digests the copepod and releases the Guinea worm larva, which penetrates the digestive tract and escapes into the body. Around a year later, the adult female worm migrates to an exit site – usually the lower leg – and induces an intensely painful blister on the skin. Eventually, the blister bursts, creating a painful wound from which the worm gradually emerges over several weeks. The wound remains painful throughout the worm's emergence, disabling the affected person for the three to ten weeks it takes the worm to emerge. The female worm releases larvae when the host submerges the wound in water in attempts to relieve the pain, thus continuing the life cycle.
There is no medication to treat or prevent dracunculiasis. Instead, the mainstay of treatment is the careful wrapping of the emerging worm around a small stick or gauze to encourage and speed up its exit. Each day, a few more centimeters of the worm emerge, and the stick is turned to maintain gentle tension. Too much tension can break and kill the worm in the wound, causing severe pain and swelling. Dracunculiasis is a disease of extreme poverty, occurring in places with poor access to clean drinking water. Prevention efforts center on filtering drinking water to remove copepods as well as public education campaigns to discourage people from soaking affected limbs in sources of drinking water, as this action allows the worms to spread their larvae.