- Byname:
- oncho
- Also called:
- onchocercosis or river blindness
- Related Topics:
- filariasis
- ivermectin
- Onchocerca volvulus
onchocerciasis
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What is onchocerciasis?
Onchocerciasis, also known as river blindness, is a filarial disease caused by the helminth Onchocerca volvulus. Black flies transmit the disease to humans through bites. This condition is prevalent in areas of Brazil and Venezuela in the Americas, as well as in sub-Saharan Africa.
The disease can cause disintegration of microfilariae in the eye, which can damage surrounding tissue and cause blindness if left untreated. Other symptoms include skin changes, such as altered pigmentation, swelling, and severe itching. Nodules may also appear in the pelvic region, upper thorax, or head region.
Ivermectin is a drug used to treat onchocerciasis by eliminating microfilariae. The WHO began distributing it in 1987.
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What causes onchocerciasis in humans?
Onchocerciasis, also known as river blindness, is a filarial disease caused by the helminth Onchocerca volvulus. It is transmitted to humans through the bite of black flies of the genus Simulium. These flies breed along fast-moving streams, and the disease is widespread in sub-Saharan Africa as well as parts of Latin America.
The disease can cause changes in skin pigmentation, dermal swelling, papules, and lichenification of the skin. Severe itching is common in newly acquired infections. Nodules may also grow in the pelvic region or in the upper thorax and head region. The infection may also invade the eyes, and blindness results in about 5 percent of infected individuals.
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How is onchocerciasis spread to people?
Onchocerciasis, also known as river blindness, is a filarial disease transmitted to humans through the bite of black flies of the genus Simulium. These flies breed in fast-moving streams and rivers, which is why the disease is common in riverine populations.
The Onchocerca volvulus worms cause the disease. The flies transmit larvae into the human body, and the dead larvae can cause blindness by damaging surrounding tissue in the eye. Other symptoms include skin changes, such as itching, swelling, and nodules. Onchocerciasis is mainly found in sub-Saharan Africa, but it has also been reported in northern Sudan and Yemen.
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What happens to the body when someone has onchocerciasis?
Onchocerciasis, also known as river blindness, is a disease where the flies that transmit the disease breed on rivers, mostly affecting riverine populations. Dead microfilariae, larvae produced over 15 to 18 years by adult worms, cause blindness inside the eye. These disintegrating bodies damage surrounding tissue, often the cornea, resulting in blindness if the reproducing adult worms are not attacked. Other symptoms include changes in skin pigmentation, dermal swelling, papules, and lichenification of the skin. Severe itching is common in newly acquired infections. Nodules, which may grow as large as a pigeon egg, are found in the pelvic region or in the upper thorax and head region.
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What are the main symptoms and physical effects of onchocerciasis?
Onchocerciasis, also known as river blindness, is a filarial disease caused by the nematode Onchocerca volvulus, transmitted through flies of the genus Simulium. These flies breed along fast-moving streams, which is why the disease is called river blindness.
Key symptoms include severe itching, changes in skin pigmentation, dermal swelling, papules, and lichenification of the skin. Nodules, which can grow quite large, may appear in the pelvic region or the upper thorax and head region.
The most severe effect is blindness, caused when dead microfilariae (larvae produced by adult worms) disintegrate inside the eye, damaging surrounding tissue, particularly the cornea. In Yemen and northern Sudan, a form called sowda, localized in one leg, is most common.
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How do the worms involved in onchocerciasis cause damage to the skin and eyes?
Onchocerciasis, also known as river blindness, is a filarial disease caused by the helminth Onchocerca volvulus, transmitted by black flies. The disease manifests through various symptoms, including skin changes like altered pigmentation, swelling, and itching.
The damage to the eyes, potentially leading to blindness, is caused by dead microfilariae (larvae produced by adult worms) within the eye, which damage surrounding tissue, particularly the cornea. If the reproducing adult worms are not addressed, blindness can result. Nodules may also appear under the skin, typically in the head region.
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onchocerciasis, filarial disease caused by the helminth Onchocerca volvulus, which is transmitted to humans by the bite of black flies in the genus Simulium. The disease is found chiefly in Brazil 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 northern Sudan and Yemen.
Disease course and symptoms
Onchocerciasis is often called river blindness 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 blindness will result if the reproducing adult worms are not attacked. River blindness is common in savanna areas of Africa. In the forest areas (as opposed to the savanna), 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.
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Treatment
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 (WHO) 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 generally safe and effective.
Elimination efforts
In 1974 WHO undertook the eradication of the black fly in West Africa. However, considering the life span 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.
In 1992 the Carter Center, in partnership with health ministries, the Pan-American Health Organization, the U.S. Centers for Disease Control and Prevention, and various other independent organizations and academic institutions, initiated the Onchocerciasis Elimination Program of the Americas (OEPA). By 2021, through the OEPA, onchocerciasis transmission had been eliminated from 11 of 13 endemic areas in the Americas. The first country to be certified by WHO as being free from onchocerciasis transmission was Colombia, in 2013. Ecuador, Mexico, and Guatemala followed soon after.