/ong'koh seuhr kuy"euh sis/, n. Pathol.
an infestation with filarial worms of the genus Onchocerca, common in tropical America and Africa, transmitted by black flies, and characterized by nodules under the skin, an itchy rash, eye lesions, and in severe cases, elephantiasis.
Also, onchocercosis /ong'koh seuhr koh"sis/. Also called river blindness.
[1910-15; < NL Onchocerc(a) a genus of filarioid worms (oncho- (correctly onco- < Gk ónk(os) barb + -o- -O-) + -cerca fem. of -cercus -tailed < Gk, adj. deriv. of kérkos tail) + -IASIS]

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byname  oncho , also called  onchocercosis 
 filarial disease caused by the helminth Onchocerca volvulus, which is transmitted to humans by the bite of the black fly Simulium. The disease is found chiefly in Mexico, Guatemala, and Venezuela in the Americas and in sub-Saharan Africa in a broad belt extending from Senegal on the west coast to Ethiopia on the east; in Africa its northern edge is about 15° N of the equator, and it extends as far south as Angola and Tanzania. It has also been reported in Colombia, northern Sudan, and Yemen.

      Probably the best-known form of onchocerciasis is also known as river blindness. It has this name because the flies that transmit the disease breed on rivers and mostly affect riverine populations. Blindness is caused by dead microfilariae—the larvae that can be produced for some 15 to 18 years by adult worms—inside the eye. These disintegrating bodies damage surrounding tissue (often the cornea), and if the reproducing adult worms are not attacked, blindness will result. “River blindness” is common in savannah areas of Africa and in Guatemala and Mexico. In the forest areas (as opposed to the savannah), transmission of onchocerciasis is perennial rather than seasonal and blindness is rare.

      Other symptoms of the disease include changes in skin pigmentation, dermal swelling, papules, and lichenification of the skin. In newly acquired infections severe itching is common. Nodules that may grow as large as a pigeon egg are found in the pelvic region or in the upper thorax and head region. In Yemen and northern Sudan a type of onchocerciasis called sowda, with infection localized in one leg, is the most common form.

      In 1974 the World Health Organization undertook the eradication of the black fly in West Africa, but, considering the lifespan of Onchocerca and the distance that certain species of black fly can travel (up to 400 miles [640 km] in one day), the success of the program would not be certain for many years to come.

      Until 1987, treatment was generally with diethylcarbamazine, which can remove microfilariae from the skin, or with suramin, a potent and dangerous drug that affects both the adult worm and the microfilariae. In 1987, however, the World Health Organization began to distribute a drug known as ivermectin, originally developed in the 1970s for use against livestock parasites. Though it does not kill the adult parasite, it eliminates the microfilariae and is surprisingly safe and effective.

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Universalium. 2010.

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  • Onchocerciasis — River blindness, a disease caused by a parasitic worm (Onchocerca volvulus) which is transmitted to persons by biting blackflies (buffalo gnats) that breed in fast flowing rivers. The adult worms can live for up to 15 years in nodules beneath the …   Medical dictionary

  • onchocerciasis — n. a tropical disease of the skin and underlying connective tissue caused by the parasitic worm Onchocerca volvulus. Fibrous nodular tumours grow around the adult worms in the skin; these may take several months to appear, and if secondary… …   The new mediacal dictionary

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  • onchocerciasis — noun /ɒŋkəsɜːˈkaɪəsɪs/ A disease caused by a worm of the genus Onchocerca, especially as transmitted to humans by flies and often causing blindness; common in tropical Africa. Syn: river blindness …   Wiktionary

  • onchocerciasis — [ˌɒŋkəʊsə: sʌɪəsɪs, kʌɪəsɪs] noun technical term for river blindness. Origin early 20th cent.: from mod. L. Onchocerca (genus name of the parasite causing the disease, from Gk onkos barb + kerkos tail ) + iasis …   English new terms dictionary

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