Onchocerciasis, also known as “river blindness,” still affects millions of people living near rivers and wetlands in Africa. Fortunately, this disease can be prevented through a simple, free treatment that is distributed annually within communities. To better understand it's transmission, who is most exposed, and what progress has been made, we spoke with Dr. Didier Bakajika, expert at WHO Africa.

1. What is river blindness and how is it transmitted?

River blindness, or onchocerciasis, is a disease caused by a small parasite transmitted by tiny blackflies that live near rivers with rapids and fast-flowing water. When someone is bitten, the flies can transmit thousands of parasite larvae. These larvae settle in the skin and develop into adult worms that produce microfilariae which, over time, can affect eyesight — hence the name “river blindness.”

2. Who is most at risk, and why are certain areas more affected?

People who live or work near these rivers are the most exposed. These areas are ideal breeding sites for blackflies. Villages located close to such zones are therefore more affected, due to frequent bittings over many years. Even those living farther away can be at risk, as adult female blackflies can travel long distances in search of human blood.

3. Can people protect themselves without treatment?

It is difficult to be fully protected, because blackflies are very small and mainly bite during the day. However, some measures can reduce the risk: avoiding areas where they are abundant, wearing protective clothing, and limiting time spent near fast‑flowing rivers.

But the most effective protection remains the annual treatment. If you live in an endemic area, there is no other reliable method: you must take the medicine every year to stay protected. This treatment protects not only the person who receives i,t but the entire community.

4. How does the treatment work, and why must it be taken regularly?

The treatment consists of taking Mectizan, a free medication given once a year. The dose is adjusted according to each person’s weight or height. This treatment kills the young parasites, or microfilariae, present in the body and protects against complications, particularly those affecting the skin and eyesight.

Since adult parasites live for many years, it is essential to take Mectizan annually for several years to interrupt transmission sustainably.

5. How do communities contribute to the success of treatment campaigns?

Communities play a crucial role. They select volunteers who are trained to distribute Mectizan tablets within each community. These volunteers know the residents well, which helps with awareness‑raising, distribution, and treatment follow‑up. Their commitment is one of the key factors in the program’s success and long‑term sustainability.

6. What recent progress has been made in Africa?

To date, Niger is the only African country to have eliminated onchocerciasis transmission. Each year, mass treatment campaigns with Mectizan reach millions of people through the joint efforts of governments, community volunteers, and technical and financial partners. In several countries, progress is tangible: 24.8 million people living in 208 health districts across eight countries no longer require mass treatment for onchocerciasis.