MORPHLOGY Dracunculiasis, also known as Guinea worm disease, is caused by the large female nematode, Dracunculus medinensis, which is among the longest nematodes infecting humans. The adult female is primarily larger than the adult male. The longest adult female recorded was 800 mm (31 in), while the adult male was only 40 mm (1.6 in). Mature female worms migrate along subcutaneous tissues to reach the skin below the knee, forming a painful ulcerating blister. They can also emerge from other parts of the body, such as the head, torso, upper extremities, buttocks, and genitalia.
EPIDEMIOLOGY A person gets infected, by drinking water from stagnant sources (e.g., ponds) contaminated with copepods containing immature forms of the parasite (juveniles), which have been previously released from the skin of a definitive host. The infection can also be acquired by eating a fish paratenic host, but this is rare. The parasite is known to be found in Africa and India. No reservoir hosts are known, that is, each generation of worms must pass through a human.
LIFE CYCLE Humans become infected by drinking unfiltered water containing copepods (small crustaceans) that have been infected with D. medinensis larvae. After ingestion, the copepods die and release the stage 3 larvae, which then penetrate the host's stomach or intestinal wall, and enter into the abdominal cavity and retroperitoneal space. After maturing, adult male worms die while the females migrate in the subcutaneous tissues towards the surface of the skin. After about a year of infection, the female worm forms a blister on the skin, generally on the distal lower extremity (foot), which breaks...