River blindness Onchocerciasis

What is River blindness?

Onchocerciasis, also known as “river blindness”, is a chronic disease caused by a parasitic worm known as Onchocerca volvulus. Approximately 35 million people are suspected to be infected worldwide, with over 99 percent of those cases occurring in sub-Saharan Africa. 

How do you get River blindness?

Onchocerciasis is transmitted through the bite of an infected female blackfly. These usually bite during the day and are found near rapidly flowing streams and rivers. Onchocerciasis is not transmitted from person to person.

Susceptibility and Resistance

Everyone is presumed to be susceptible to infection with onchocerciasis, including those who have been treated for the disease in the past. Onchocerciasis increases in severity with repeated infections.

Incubation Period

The incubation period for River blindness is 270-365 days.

What are the Symptoms?

Onchocerciasis is an ongoing and nonfatal infection that causes various symptoms involving the skin, such as the formation of large, hard lumps under the skin, particularly in the head, shoulders, pelvic area and lower extremities. Other symptoms include an itchy, bumpy rash, disfiguring skin lesions and thinning, swelling, and discoloration of the skin. Lesions in the eye can progress to visual impairment and blindness, hence the disease is called “river blindness”.

Preventative Measures

No vaccination or drugs are available to prevent this infection.  Avoid blackfly habitats and bites by using personal protection measures against biting insects.


Onchocerciasis can usually be treated with a single oral dose of an anti-parasitic drug, known as Ivermectin, once or twice per year. However, repeated doses might be required if the adult worms are not killed. Some health care professionals recommend a 3 to 4 week treatment with doxycycline (an antibiotic medication) if there is no risk of re-infection. Doxycycline cannot be used in children less than eight years of age. Research is currently underway in an attempt to find safe and effective drugs that will sterilize or kill the adult worms. 

The large lumps that form under the skin can be easily removed under local anesthesia.


Where Does It Commonly Occur?

The disease occurs in 25 countries across central Africa, the Arabian Peninsula, and in Central and South America.