Generality/Definition
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River Blindness, or Onchocerciasis, is the world's second leading cause of blindness. It is a parasitic disease caused by a parasitic worm (Onchocerca volvulus) that can live in the human body for up to 14 years. The larval forms of these parasitic worms are introduced in the human body, as well as transmitted from a sick person to a healthy one, via the bite of infected blackflies (Simulium) that live and breed in fast flowing rivers because of their highly oxygenated water. Once the thousands of microfilariae (microscopic larvae) produced by the female worm spread throughout the body and reach the eye they can cause a variety of conditions including serious visual impairment and blindness.
Source: River Blindness (uniteforsight.org)
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Onchocerciasis is a disease caused by the invasion of the organism by threadlike worms called filaria belonging to the species Onchocerca volvulus. Its gravity is due to the fact that it very frequently gives rise to blindness in populations living on the banks of rivers, whence its name river blindness. It rages especially in Africa but also in Central America and in a little breeding ground in Yemen, regions into which the disease has been introduced by groups of slaves since the fifteenth century. It rages especially in Africa but also in Central America and in a little breeding ground in Yemen. The role of Onchocerciasis in the development of eye troubles was recognized at a late date, in 1919. All the eye tissues can be affected : the cornea, the iris, the ciliary body, the membrane of the retina and the optic nerve.
In front of the main entrance of the WHO Headquarters in Geneva, a commemorative statue has been erected. On the base of the monument there is a plaque that tells passers-by :
This distressing depiction of a child guiding an adult who has lost his sight after having contracted the river blindness, a plague that afflicts poor communities. At the end of the track was a common sight in wide areas, and most particularly in Africa. By uniting their efforts in an outstanding partnership, the onchoceriasis control programme in West Africa, the African program of fight against onchoceriasis and the eradication programme of onchoceriasis in the Americas have relieved humanity of this incapacitating disease, thus contributing to reduce poverty.
Source: Onchocerciasis or River Blindness (asnom.org)
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Epidemiology
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Onchocerciasis causes chronic suffering and severe disability among 18 million people worldwide, of whom 300,000 are irreversibly blind. The disease is mostly encountered in the Western and Central Africa, and to a lesser extent in the Middle East and the Americas.
Source: River Blindness (uniteforsight.org)
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Onchocerciasis is a major cause of blindness in many African countries. As a public health problem, the disease is most closely associated with West and Central Africa, but it is also prevalent in Yemen and six countries in Latin America. Onchocerciasis has in the past greatly reduced the economic productivity in infected areas and left vast tracts of arable land abandoned. It is estimated that there are about half a million blind people due to river blindness.
Source: WHO | VISION 2020 priority eye diseases (v2020.org)
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Prevention
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Much progress has been made in fighting the disease in several countries through control of the blackfly, however, the disease can now also be treated with an annual dose of the drug ivermectine, Mectizan, which also relieves the severe skin itching caused by the disease.
Source: WHO | VISION 2020 priority eye diseases (v2020.org)
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Symptoms
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Aside from being a leading cause of blindness, people suffering from River Blindness experience severe and continuous itching due to the presence of nodules that develop under the skin, causing them to scratch repeatedly. As a result, the damaged skin areas suffer a loss of pigmentation and, over the time, the skin becomes spotty, which causes de-pigmented spots that are more susceptible to skin cancer.
Source: River Blindness (uniteforsight.org)
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Treatment
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An other aspect of the fight against onchocerciasis is chemioprophylaxy. In the early 1980s, a tremendous progress was made when ivermectine (approved in 1987) was launched under the name of mectizan. It is well tolerated by patients. Taking a tablet once every six months destroys the microfilaria and inhibits the egg-laying of adult filaria. Its use from 1980, together with the campaign against disease carriers (vectors), gives hope that, with the support of international solidarity, this epidemic could one day disappear altogether from intertropical Africa.
Source: Onchocerciasis or River Blindness (asnom.org)
Illustrations
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