A tropical disease, also called river blindness, caused by the worm ONCHOCERCA VOLVULUS.
The disease is a type of filariasis transmitted by simulium flies.
The worms’ dead larvae can lead to blindness if they cause an allergic reaction in or near the eyes.
Treatment is with anthelmintic drugs.
Infestation with the ?larial worm, Onchocerca volvulus, found in many parts of tropical Africa, in Central and South America, and in the Yemen and Saudi Arabia. After a period of 9–18 months, the young ?larial worms, injected into the body by the bite of an infected simulium gnat, mature, mate and start producing young micro?lariae. The females live for up to 15 years and during this period each may produce several thousand micro?lariae a day. It is these micro?lariae, which have a life-span of up to two years, that produce the characteristic features of the disease: an itching rash of the skin and the appearance of nodules in di?erent parts of the body. The worm may invade the optic nerve of the EYE and so cause blindness; hence the name of African river-blindness. Treatment consists of diethylcarbamazine and suramin. An international campaign is now underway in an attempt to destroy simulium in the affected zones.
(Syn. “river blindness”) A. disease caused by the parasitic filarial nematode Onchocerca volvulus. (See also filariasis).
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 bacterial infection occurs they may degenerate into abscesses. The skin also becomes inflamed and itches. The migration of the *microfilariae into the eye can cause total or partial blindness – called river blindness in Africa. Onchocerciasis occurs in Africa and Central and South America. *Ivermectin is used in treatment; if possible, the nodules are removed as and when they appear.
n. the inability to see. Lack of all light perception constitutes total blindness but there are degrees of visual impairment far less severe than this that may be classed as blindness for administrative or statutory purposes. For example, marked reduction in the *visual field is classified as blindness, even if objects are still seen sharply. The commonest causes of blindness worldwide are *trachoma, *onchocerciasis, and vitamin A deficiency (see night blindness) but there is wide geographic variation. In Great Britain the commonest causes are age-related *macular degeneration, *glaucoma, *cataract, myopic retinal degeneration, and diabetic *retinopathy.... blindness
n. a drug used in the treatment of *onchocerciasis. It acts by killing the immature forms (*microfilariae) of the parasite. Ivermectin is also used to treat creeping eruption, strongyloidiasis, and scabies. Side-effects, which are mild, include itching and swollen lymph nodes.... ivermectin
n. a genus of parasitic worms (see filaria) occurring in central Africa and central America. The adult worms are found in fibrous nodules within the connective tissues beneath the skin and their presence causes disease (see onchocerciasis). Various species of black fly, in which Onchocerca undergoes part of its development, transmit the infective larvae to humans.... onchocerca
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