DRACUNCULOSIS

Guinea worm, or dracunculosis, is a helminth infection. The adult female worm is about a meter in length and a millimeter in diameter. It lives in subcutaneous tissue, often embracing a male worm. Males are about 2.5 centimeters long. The female consists almost entirely of a uterus to produce eggs that are disgorged into fresh water through an ulcer on the skin, usually on the lower legs of infected individuals. The eggs are ingested by fresh water crustaceans that are small enough to be swallowed when humans drink the water. The larvae mature and migrate through soft tissue to reach their final destination just under the skin.

Until the 1980s, guinea worm infection affected about 125 million people all across equatorial Africa, the Arabian peninsula, Iran, Afghanistan, and the Indian subcontinent. Prevention campaigns based on water filtration, education, and treatment of affected people have succeeded in eradicating dracunculosis from India, which was declared free of infection early in 2000 after zero case reports since 1996, and have reduced the total number of cases worldwide to an estimated 100,000, mostly in West Africa and Yemen, by late 1999.

The worm can survive in subcutaneous tissue for years. The traditional method of removing it by winding it laboriously around a stick, withdrawing it gradually a little more each day, is still an effective way to get rid of worms, although surgical removal is also an option.

John M. Last

dracontiasis (drak-on-ty-ă-sis) n. a tropical disease caused by the parasitic nematode Dracunculus medinensis (see guinea worm). The disease is transmitted to humans via contaminated drinking water. The worm migrates to the skin surface and eventually forms a large blister, usually on the legs or arms, which bursts and may ulcerate and become infected.