What is river blindness?

River blindness, or onchocerciasis, is a parasitic infection that can cause severe skin irritation, itching and, over time, irreversible blindness.

Emmanuel fishing in the Pru River: he stands in knee-deep water while holding a fishing net.

River blindness is spread by the bite of infected black flies that breed near fast-flowing rivers.

The disease’s connection to rivers gave rise to the term ‘river blindness’, which was coined by Lady Jean Wilson, wife of Sightsavers’ founder Sir John Wilson. It is one of a group of conditions known as neglected tropical diseases (NTDs).

When someone is bitten by the flies, worm larvae invade the body through the bite. These larvae develop into worms that can live for 15 years. Female worms produce thousands of microscopic larvae, known as ‘microfilariae’, each day, which spread through the body and can be passed on to others. When the microfilariae die, they cause a reaction in the body, leading to immense irritation, inflammation and itching. If the larvae travel to the eyes and cause a reaction, irreversible eyesight damage and sight loss can occur.

As well as pain, blindness and the associated stigma, one of the devastating outcomes of river blindness is that people are forced to move away from fertile river valleys where the disease is prevalent. As a result, people can struggle to find suitable areas to farm or grow crops, pushing families and communities into poverty.

120 million
people worldwide are at risk of contracting river blindness
37 million
people are infected. Most live in sub-Saharan Africa
people worldwide are blind because of the disease

How is river blindness treated?


Mectizan® tablets can prevent the disease spreading. They don't cure blindness, but can help to stop any further sight loss.


Mectizan®, donated by Merck Sharpe & Dohme, is distributed via local volunteers known as community-directed distributors.

A man examines black fly larvae found near the the Agogo river in northern Uganda.


River blindness is also addressed by eradicating the flies that carry the disease, a process that is known as vector control.

What we’re doing

Sightsavers is working to eliminate river blindness in the countries in which we work by 2025.

Traditionally, river blindness and lymphatic filariasis have been treated through individual treatment programmes. But because they are often detected in the same areas and can both be treated with Mectizan® tablets, Sightsavers treats both of the diseases together.

In 2016, Sightsavers helped to distribute almost 47 million treatments for river blindness. Since our work began 65 years ago, we’ve provided more than 389 million treatments worldwide to protect eyesight.

Find out about other diseases we treat

Neglected tropical diseases

More about river blindness

7 year old Dorcas is standing outside, smiling. She is the one billionth treatment beneficiary.
News / NTDs /

Sightsavers and partners celebrate delivering a billion NTD treatments

The billionth treatment was administered on Thursday 16 November to a seven-year-old girl named Dorcas, who was at risk of NTDs in Kaduna State, Nigeria.

District onchocerciasis co-ordinator William Mugayo and Ugandan Secretary of Health Titus Ariyo discuss the mass drug administration project during a radio broadcast with DJ Robert Musasizi.
Sightsavers Reports

How radio is saving lives in Uganda

In remote regions of Uganda, radio broadcasts are being used to spread information about diseases such as river blindness, and how they can be treated.

Fly catcher
News / NTDs /

Uganda moves one step closer to eliminating river blindness

Two more areas and more than a million people in the country have met the World Health Organization criteria for elimination of the disease.