Dracunculiasis (guineaworm infestation)
Dracunculiasis, a disease of man, which has been known since antiquity, is caused by the nematode parasite Dracunculus medinesis. The parasite is commonly known as guineaworm.
The adult parasites inhabit the subcutaneous tissues mainly of the legs, the head and the neck. The mature female parasite forces its anterior end into the dermis, thus inducing oedematous swelling, inflammatory reaction, and blister formation. Upon contact with water the blister ruptures, and from the uterus of the female large number of larvae are released. After deposition of larvae the female dies and is absorbed by the tissues.The larvae may remain active in the water for 3-6 days. Further development takes place in a suitable intermediate host, the crustacea, Cyclops. These commonly inhabit water-sources such as ponds and wells. Infected Cyclops may survive for several months. Man acquires the infection by drinking water containing infected intermediate host. In the human body the parasites are released in the gut and penetrate the duodenal wall. Subsequently they migrate via the abdominal mesenteries to the subcutaneous tissue of various parts of the body. The mature female emerges 10-14 months after infection.
Epidemiology: The term guineaworm or medina worm implies that the disease occurred in some specific locations in the past. Today, disease occurs in the East, West and North of Africa, in the Middle East, India, Iran and Pakistan.Dracunculiasis is prevalent in areas with a dry climate or with an extended dry season. Peak transmission occurs during the dry season, when the water levels of drinking – water sources are low and the dry density of infected intermediate hosts is high.Besides man, animals such as carnivores, cattle, and horses also get infected with D. medinesis. Dogs are most frequently infected. Dogs and other animals may act as reservoir hosts.
Clinical features: The infection is mostly asymptomatic for about 1 year, but clinical symptoms appear when the female migrates to the dermis. Prodromal symptoms are fever, diarrhoea, vomiting and urticaria. Specific signs of the disease are erythema, oedema, induration of the skin, as well as blister and ulcer formation at the sites where the females penetrate to the surface. The severity of symptoms depends on the location of the worm. More severe symptoms are associated with the death of worm or secondary bacterial infection.
Laboratory diagnosis: Diagnosis is based on clinical symptoms, X-ray examinations and immunodiagnostic tests such as immunofluorescence test.
Control and prevention: The disease can be controlled by the improvement of water supplies – for example, by the introduction of piped water, by the substitution of draw wells, or by the construction of tube well. Chlorination of drinking water prevents the spread of infestation. Boiling or filtering drinking water provides personal protection.