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.... onchocerciasis
Blood-sucking flies belonging to the genus Simulium. Includes the vectors of human Onchocerciasis (River Blindness) in parts of Africa and Latin America.... blackfly
a small widely distributed bloodsucking insect of the genus Simulium. Black flies are also known as buffalo gnats from their humpbacked appearance. Female flies can inflict painful bites and constitute a serious pest at certain times of the year. S. damnosum in Africa and S. ochraceum in Central America and Venezuela transmit the parasites causing *onchocerciasis.
black hairy tongue (BHT) a harmless condition characterized by the appearance of elongated filiform *papillae on the upper surface of the tongue. The usual cause is an overgrowth of bacteria that accumulate on the papillae and create pigments giving the tongue a black appearance. Known predisposing factors include smoking, excessive consumption of tea and/or coffee, poor oral hygiene, trigeminal *neuralgia, and *dry mouth.... black fly
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