Dracunculiasis, also called guinea worm disease (GWD), is an infection by the guinea worm. A person becomes infected when they drink water that contains water fleas infected with guinea worm larvae. Initially there are no symptoms. About one year later, the person develops a painful burning feeling as the female worm forms a blister in the skin, usually on the lower limb. The worm then comes out of the skin over a few weeks. During this time, it may be difficult to walk or work. It is very uncommon for the disease to cause death.Humans are the only known animal that guinea worms infect. The worm is about one to two millimeters wide and an adult female is 60 to 100 centimeters long (males are much shorter). Outside of humans the eggs can survive up to three weeks. They must be eaten by water fleas before this. The larva inside water fleas may survive up to four months. Thus the disease must occur each year in humans to stay in an area. A diagnosis of the disease can usually be made based on the signs and symptoms of the disease.Prevention is by early diagnosis of the disease and then preventing the person from putting the wound in drinking water. Other efforts include improving access to clean water and otherwise filtering water if it is not clean. Filtering through a cloth is often enough. Contaminated drinking water may be treated with a chemical called temefos to kill the larva. There is no medication or vaccine against the disease. The worm may be slowly removed over a few weeks by rolling it over a stick. The ulcers formed by the emerging worm may get infected by bacteria. Pain may continue for months after the worm has been removed.In 2013 there were 148 cases of the disease reported. This is down from 3.5 million cases in 1986. It only exists in 4 countries in Africa, down from 20 countries in the 1980s. The country most affected is South Sudan. It will likely be the first parasitic disease to be eradicated. Guinea worm disease has been known since ancient times. It is mentioned in the Egyptian medical Ebers Papyrus, dating from 1550 BC. The name dracunculiasis is derived from the Latin "affliction with little dragons", while the name "guinea worm" appeared after Europeans saw the disease on the Guinea coast of West Africa in the 17th century. A species similar to guinea worms causes disease in other animals. These do not appear to infect humans. It is classified as a neglected tropical disease.