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River Blindness (Onchocerciasis)

River blindness

What is river blindness?

River blindness or Onchocerciasis (medical name) is an infectious disease. It is so called because the transmission is most intense in remote African rural agricultural villages, located near rapidly flowing streams or rivers. The World Health Organization's (WHO) expert committee on river blindness estimates the global prevalence is 17.7 million, of whom about 270,000 are blind and another 500,000 have visual impairment. In fact, it is the world’s fourth leading cause of preventable blindness. 500,000 of those infected with onchocerciasis are severely visually impaired, and another 270,000 have been rendered permanently blind from the disease.

How do you get river blindness?

River blindness is transmitted by infected Simulium black flies living near bodies of water in Africa. Infected black flies spread worm larvae through bites on the skin. The larvae enter the body at the bite site, form subcutaneous nodules under the skin, and mature into adult worms. Female worms release millions of small larvae into the body which eventually die and lead to severe skin rashes and depigmentation, visual impairment and blindness, and severe and disfiguring skin nodules.

How do I know if I’m infected (signs & symptoms)

Persons with heavy infections will usually have one or more of the three conditions: dermatitis, eye lesions, and/or subcutaneous nodules. Superficial skin biopsies will identify the parasite microscopically. Skin symptoms consist of skin rashes and depigmentation (“leopard skin”), debilitating itching, and skin nodules. Visual impairment and blindness can also occur.

Are there places that I am at higher risk to contract river blindness?

Ninety-nine percent of all river blindness cases are found in Africa. It mostly infects people living near the rivers and fast-moving streams of Africa. A small number of cases have also been reported in Yemen and South Americas.

Can it be cured?

While currently no vaccine exists for river blindness, prevention is possible. Blackflies bite during the day. The best prevention is to avoid infective bites of the blackly by:

• Using insecticides such as DEET, and

• Wearing long sleeve shirts and pants.

As for the cure and treatment, it can be successfully treated with a drug called Ivermectin which is administered as an oral dose of 150 micrograms per kilogram (maximum 12 mg) every 6-12 months. The drug should probably not be given to pregnant women or children under 5 years. Ivermectin does not kill the adult parasites, but reduce the numbers of microfilariae in skin so the disease does not progress.

Does the disease cause any long-term affects to vision if treated early?

The most serious manifestation of river blindness consists of lesions in the eye that can progress to blindness. Persons blinded by river blindness have a life expectancy of 10 years after onset of blindness. Overall life expectancy of an infected individual in endemic areas is one-third that of an uninfected individual. However, the good news is that early and proper treatment can prevent blindness in later stage of life. In areas where river blindness is known to occur, one should seek medical testing and treatment when the first signs appear.

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