Dracunculus medinensis (Guinea worm, fiery serpent) is a nematode that causes dracunculiasis, also known as guinea worm disease. The disease is caused by the female which, at up to in length, is among the longest nematodes infecting humans. In contrast, the longest recorded male Guinea worm is only . Guinea worm is on target to be the second infectious disease of humans to be eradicated, after smallpox. It was formerly endemic to a wide swath of Africa and Eurasia; as of 2021, it remains endemic in five countries: Chad, Ethiopia, Mali, South Sudan and Angola, with most cases in Chad and Ethiopia. Guinea worm spread to Angola in , and it is now considered endemic there. Infection of domestic dogs is a serious complication in Chad. The common name "guinea worm" is derived from the Guinea region of Western Africa. History Dracunculus medinensis ("little dragon from Medina") was described in Egypt as early as the 15th century BC and possibly was the "fiery serpent" of the Israelites described in the Bible. In the mid-19th century, the nematode Camallanus lacustris, which infects freshwater fish, was discovered to develop in copepods. This led Russian naturalist Alexei Pavlovich Fedchenko to discover in 1870 that D. medinensis is similarly transmitted via copepod intermediate hosts. Life cycle D. medinensis L1 larvae are found in fresh water, where they are ingested by copepods (small crustaceans) of the genus Cyclops. Within the copepod, the D. medinensis larvae develop to an infective L3 stage within 14 days. When the infected copepod is ingested by a mammalian host drinking unfiltered water, the copepod is then dissolved by stomach acid and dies and the D. medinensis larvae are released and migrate through the wall of the mammalian intestine, and enter the abdominal cavity and retro-peritoneal space, where they mature into adults. After maturing and mating within the host, the males die and females (length 70–120 cm) migrate in subcutaneous tissue towards the skin's surface. Around a year after the infection, the female causes the formation of a blister on the skin's surface, generally on the lower extremities, though occasionally on the hand or scrotum. When the blister ruptures, the female slowly emerges over the course of several days or weeks. This causes extreme pain and irritation to the host. During those few days to hours before the worm exits the skin, the person may develop a fever, pain, or swelling