Chic African Culture

Blindness Caused By Biting Black Flies

Blindness Caused By Biting Black Flies

River Blindness is a tropical disease caused by a parasitic worm laid by biting black flies.




About 300,000 people are blind because of the parasitic worm Onchocerca volvulus from biting black flies and another 800,000 have a visual impairment. Nearly 99% of infected persons live in Africa. Precious eyesight can be saved, river blindness is one of the leading causes of preventable blindness worldwide.


Man in Tanzania Africa with River Blindness
Man in Tanzania Africa with River blindness


What is River Blindness?


River Blindness is transmitted through repeated bites by black flies that bite during the day. 


The disease is called River Blindness because the blackfly that transmits the infection lives and breeds near fast-flowing streams and rivers and the infection can result in blindness.

Humans become infected when blackflies deposit Onchocerca infective larvae into the skin when biting to extract blood. Once inside the human body, the larvae mature into adults in around 3 months to 1 year. Most adult female worms live in fibrous nodules under the skin and sometimes near muscles and joints.

Adult male worms are usually found near the female worms. Nodules form around the worms as part of the interaction between the parasite and its human host. Inside the nodules, the worms are relatively safe from the human immune response.

As adults, female worms produce thousands of new larvae daily. The larvae become detectable in the skin 10 to 20 months after the initial infection. The adult worms can live up to 15 years inside the human body, and their larvae have a lifespan of up to 2 years.

The death of microfilariae is very toxic to the skin and the eye, producing terrible itching and various eye manifestations (lesions). After repeated years of exposure, these lesions may lead to irreversible blindness and disfiguration skin diseases sometimes named leopard skin and lizard skin.

How Common is River Blindness?


Worldwide river blindness is second only to trachoma as an infectious cause of preventable blindness.
Eye exam

Worldwide river blindness is second only to trachoma as an infectious cause of preventable blindness. In some West African communities, the disease had blinded about 50% of men over the age of 40 years. 

People with major river blindness infections will usually have one or more of three conditions of itchy skin rash, eye disease, and/or nodules under the skin.

The World Health Organization estimates that at least 25 million people are infected and 123 million people live in areas that put them at risk of infection. About 300,000 people are blind because of the parasite and another 800,000 have visual impairment. 

Nearly 99% of infected persons live in Africa. River Blindness is commonly treated with an oral medicine called ivermectin, however; there is neither a vaccine nor recommended drug available to prevent River Blindness.



Did you know?


Trachoma is the world's leading cause of preventable blindness and occurs where people live in overcrowded conditions with limited access to water and health care. 

Trachoma, an eye infection affecting both eyes, is the world's leading cause of preventable blindness. According to the World Health Organization (WHO), trachoma is responsible for the visual impairment of 2.2 million people, of whom 1.2 million are irreversibly blind. 



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