Dracunculiasis (guinea worm disease) is caused by the nematode (roundworm) Dracunculus medinensis.
Humans become infected by drinking unfiltered water containing copepods (small crustaceans) which 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 to 120 cm) migrate in the subcutaneous tissues towards the skin surface . Approximately one 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 two weeks (and two molts) have developed into infective larvae . Ingestion of the copepods closes the cycle .
Life cycle image and information courtesy of DPDx.