Abstract

Dracunculiasis is an infection caused by the nematode Dracunculus medinensis, also known as the Guinea worm. In ancient times, the presence of dracunculiasis can be inferred from the universally recognized symbol of medicine, the rod of Asclepius, which consists of a one-headed snake wrapped around a stick. The symptoms are a painful, inflamed skin lesion containing an adult worm and debilitating arthritis. The diagnosis is made on the basis of examination; treatment consists in slow removal of the adult worm. Humans become infected through drinking water containing infected microcrustaceans, also known as copepods. Washing fruits in contaminated water or taking a bath in contaminated water can also cause the infection. The larvae are released, they penetrate the bowel wall, and mature into adult worms in about one year. The gravid female migrates through subcutaneous tissues, usually to the distal lower extremities. The cephalic end of the worm produces an indurated papule that vesiculates and eventually ulcerates. On contact with water, a loop of the uterus prolapses through the skin and discharges motile larvae. Worms that fail to reach the skin die and disintegrate or become calcified. In most endemic areas, transmission is seasonal and each infectious episode lasts about one year.
Infection is initially asymptomatic, symptoms usually develop with eruption of the worm. Local symptoms include intense itching and burning pain at the site of the skin lesion. Urticaria, erythema, dyspnea and pruritus are thought to refl ect allergic reactions to worm antigens. If the worm is broken during expulsion or extraction, a severe inflammatory reaction ensues with disabling pain. Symptoms subside and the ulcer heals once the adult worm is expelled. In about 50% of cases, secondary bacterial infections occur along the track of the emerging worm. Chronic sequelae include fibrous ankylosis of joints and contractio of tendons. The diagnosis is obvious once the white, filamentous adult worm appears at the cutaneous ulcer. Calcified worms can be localized with x-ray examination, serodiagnostic tests are not specific.
Treatment consists in slow removal of the adult worm over days to weeks by rolling it on a stick (a few centimeters per day). Surgical removal under local anaesthesia is an option but is seldom available in endemic areas. Tiabendazole, metronidazole and mebendazole have no effect against the parasite but may relieve the symptoms. Topical antibiotics with hydrocortisone are used in prophylaxis of secondary bacterial infection. These  medications may also speed up the extraction of the parasite.
Filtering drinking water through a piece of cheesecloth, chlorination, or boiling protects effectively against dracunculiasis. During the last 30 years, efforts to eradicate the guinea worm have been undertaken, which have resulted in a reduction of more than 99% cases of dracunculiasis worldwide (from 3.5 million to a couple of thousand).  The current incidence of the disease is low and is limited specifically to sub-Saharan Africa. By the end of 2008, dracunculiasis was endemic in 6 countries (Ethiopia, Ghana, Mali, Niger, Nigeria, and Sudan), and the number of cases decreased 52% (from 9,585 in 2007 to 4,619 in 2008). Sporadic violence and civil unrest in Sudan and Mali pose the greatest threat to the final eradication of dracunculiasis.