What is river blindness?

River blindness, or onchocerciasis, is a parasitic infection spread by flies that live near fast-flowing rivers. It causes severe skin irritation, itching and, eventually, irreversible blindness.

A close-up of a plastic vial containing the flies that transmit river blindness.

River blindness is spread by the bite of infected 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 and 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 leading to immense irritation, inflammation and itching. If the larvae travel to the eyes, it can cause irreversible sight loss.

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

Watch our video to find out more about river blindness.

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

How is river blindness treated?

A photo of two hands. In one hand there are three tablets.


Medication can help to prevent the disease spreading. It doesn’t cure blindness, but can help to stop any further sight loss.

Community drug distributors James and Elizabeth check medication for trachoma in Kenya.


Tablets donated by Merck Sharpe & Dohme are distributed via local volunteers known as community-directed distributors.

A close-up showing black flies on a blade of grass


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 programmes. But because they are often detected in the same areas and can both be treated with medication, Sightsavers treats both of the diseases together using mass drug administration.

In 2022, Sightsavers helped to distribute more than 44 million treatments for river blindness. Since our work began 70 years ago, we’ve provided more than 11.8 million operations worldwide to protect eyesight.

As part of our push to eliminate river blindness, in November 2017 we achieved a historic milestone: distributing the one billionth treatment to people affected by neglected tropical diseases. The billionth treatment, an antibiotic for river blindness and lymphatic filariasis, was administered to a seven-year-old girl named Dorcas, who was at risk of NTDs in a community in Kaduna State, Nigeria.

A man and a woman stand outside before beginning surveys for the Onchocerciaisis Elimination Mapping project.

“I feel I’m making a difference”

Meet Clécio Sitoe and Silvia Danga, who are helping to track the prevalence of river blindness in Mozambique.

Read their story

Find out about other diseases we treat

Neglected tropical diseases

More about river blindness

Sightsavers blog

Expanding the Reaching the Last Mile Fund: a game-changer for river blindness and lymphatic filariasis

Sightsavers’ Phil Downs explains why the funding pledge is a huge step towards tackling the two neglected tropical diseases and eliminating them for good.

Phil Downs, December 2023
Simon Bush.

Sightsavers director rewarded for his work on neglected tropical diseases

Sightsavers’ Simon Bush has received a lifetime achievement award for his work on river blindness, and has been named president of the Royal Society of Tropical Medicine and Hygiene.

October 2022
Four men sit on the back of a white truck with a Sightsavers logo on the door. They're driving through a dusty road in Mali, with trees on either side.
Sightsavers from the field

The last mile: paving the way to eliminating river blindness in Mali

Since 1991, Sightsavers been helping Mali’s ministry of health to treat and prevent this blinding disease. Now the country is on track to banish it for good.

June 2022