Dracunculiasis is caused by the nematode Dracunculus medinensis, or Guinea worm. It causes chronic cutaneous ulcers with protruding worms in rural Africa. It was a major cause of disability, but recent control efforts have been remarkably successful. Annual incidence has decreased from about 3.5 million cases in the late 1980s to 15 reported cases in 2021; recent cases were from Chad, Ethiopia, South Sudan, Mali, and Angola. Remarkably, the first case ever described in Angola was reported in 2018. Of concern, infection has also been identified in domestic dogs and cats in endemic countries, with dogs likely providing an important disease reservoir, and reported animal cases now outnumber human cases.
Infection occurs after swallowing water containing the infected intermediate host, the crustacean Cyclops (known as copepods or water fleas). In the stomach, larvae escape from the copepods and migrate through the intestinal mucosa to the retroperitoneum, where mating occurs. Females then migrate to subcutaneous tissue, usually of the legs, over about a year (eFigure 37–40). A subcutaneous ulcer then forms (eFigure 37–41). Upon contact with water, the parasite discharges large numbers of larvae, which are ingested by copepods. Adult worms, which can be up to a meter in length, are gradually extruded. Worm death and disintegration in tissue may provoke a severe inflammatory reaction.
Worm blister caused by the head of a female Guinea worm (Dracunculus medinensis). A: The female Guinea worm induces a painful blister. B: After rupture of the blister, the worm emerges as a whitish filament in the center of a painful ulcer, which is often secondarily infected. (Reproduced with permission from Global 2000/The Carter Center, Atlanta, Georgia.)
Life cycle of Dracunculus medinensis (Guinea worm). Humans become infected by drinking unfiltered water containing copepods (small crustaceans) that are infected with larvae of D medinensis
. Following ingestion, the copepods die and release the larvae, which penetrate the host stomach and intestinal wall and enter the abdominal cavity and retroperitoneal space
. After maturation into adults and copulation, the male worms die and the females (length: 70–120 cm) migrate in the subcutaneous tissues toward the skin surface
. Approximately 1 year after infection, the female worm induces a blister on the skin, generally on the distal lower extremity, which ruptures. When this lesion comes into contact with water, a contact that the patient seeks to relieve the local discomfort, the female worm emerges and releases larvae
. The larvae are ingested by a copepod
and after 2 weeks (and two molts) have developed into ...