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

For more than 30 years, Sightsavers has been working alongside the government of Mali to fight river blindness, a debilitating neglected tropical disease.

River blindness (also known as onchocerciasis) is spread by the bite of infected black flies, which breed near fast-flowing rivers. If left untreated, it can cause irreversible blindness.

Mali was one of the first countries to use community volunteers to distribute treatment for the disease, and the approach is now used across NTD programmes.

In 2021, Sightsavers helped to carry out a large-scale survey in Mali to find out if mass drug treatment is still needed to eliminate river blindness. Here we reflect on our work in the country, and look at the final steps needed for Mali to banish the disease for good.

In 1991, Elie Kamate was a programme officer working for Sightsavers’ onchocerciasis elimination programme in Mali. He was subsequently promoted to country director and now works as a senior consultant.

“I started my activities on the river blindness project in 1991 working in the Kati district,” explains Elie. “Over the years we’ve been focusing on mass drug administration (MDA) and we’ve come a very long way.

“The first village I visited was Fougadoudou village in 1993: what I saw was a disaster. There were only about 100 people living there and most were children, women and older people. The young people and men had abandoned the village because of river blindness; they were so scared to contract the disease and become blind,” says Elie.

Mali stretches across three different climatic regions: the south is a tropical environment, with the Niger and Senegal rivers and their tributaries running through it. This enabled river blindness to spread to the nearby communities, where residents rely on the rivers for their income.

Thanks to the efforts of the ministry of health and the communities themselves, the situation has changed substantially after several years of treatment programmes to protect people against river blindness..

“The last time I visited Fougadoudou, I was really happy to see all the activities running in the village,” Elie says. “There are now factories and young people working there. This village, which was once abandoned because of the threat of river blindness, is now reoccupied thanks to successes in the fight against the disease.”

To reach elimination, Mali must prove that the disease is no longer a public health risk to the country, that drug distribution campaigns can stop, and that individual infections can be managed by the health system. To determine if the country is near this stage, a survey (known as a ‘stop MDA survey’) must be carried out.

Dr Yacouba Sangare, coordinator of the National Onchocerciasis Control Programme, helped to lead the survey in Mali.

“The stop MDA surveys are very exciting and are thanks to the efforts of those who have worked tirelessly to get to this point,” says Dr Sangare. “To reach elimination requires several steps, but when we are free of this disease it’ll be exciting for us and for the next generation.”

The stop MDA survey consists of two parts. Blood spot samples are collected from children to help determine that there is no new infection in the community, and flies are examined to see if they still carry the parasites that cause river blindness. Both parts of the survey help determine the prevalence of river blindness. If the prevalence of the disease is low, Mali can stop mass treatment for the disease and enter a surveillance phase before declaring it has eliminated the disease.

Step 1: Blood spot sample surveys

To find out if river blindness is still in the community, children aged five to nine are tested for the disease using blood spot samples. To collect a sample, a community health worker pricks the tip of the child’s finger and applies the blood to special filter paper.

Once the blood spots are collected, they are brought to the lab to be tested. If the children test positive for river blindness, it shows the transmission of the disease is ongoing and the community requires further treatment.

Step 2: Fly-catching surveys

The second portion of the stop MDA survey is to study black flies collected in the communities to see if they carry the parasite that causes river blindness. Collecting and analysing black fly data can be challenging, and at present the only reliable way to monitor for infected flies is by using human ‘fly catchers’, who are given preventative treatment to protect them from the risk of catching river blindness.

The fly catchers start their day at 7am. During the survey they sit near the river and wait for the flies to land on them: when they spot one, they catch it in a test tube before it has a chance to bite them. They also record how many flies they caught each hour and each day, to monitor how many there are in the area. The flies are then brought to a lab to test whether they are carrying the disease.

Soumaila, one of the fly catchers in the Koulikoro region of Mali, joined the project due to his own experience of river blindness. “I caught the disease when I was 25, which caused a legion to grow on my neck and my vision was starting to go blurry,” Soumaila says. “I was very afraid of the disease.”

Thankfully, Soumaila’s infection was caught early, and he received treatment for the disease. But he will always remember what it was like before treatment was readily available.

“When I was a child, if you came to visit our village you could find between 50 to 100 people with river blindness. We spent our childhood taking care of adults who couldn’t do anything because they were blind. Thanks to the treatment, today there are very few newly blind people in our village.”

Mamourou, a farmer in the Koulikoro region, was infected by river blindness before treatment was readily available. “I first started losing my sight when I was in my field behind the river,” Mamourou says. “That’s where I was bitten by the black flies. Eventually, my vision diminished and then I could only see black.”

Mamourou’s sight is now completely gone in one eye and blurred in the other. Although his sight can’t be restored, he has hope for the future. “I’m very happy about the idea that Mali could be close to eliminating the disease. I hope it disappears so that it no longer affects our children.”

If the results of the stop MDA survey find that the prevalence of river blindness is low enough, the country will be able to stop mass treatment for the disease. Results should be ready later this year.

“After we stop treatment, we will have a surveillance plan for three to five years to make sure there are no new cases,” says Dr Sangare. “Then we can start preparing for elimination. If we can eliminate the disease, it will be a great joy for us. Our elders will be very proud of us and would be an honour to accomplish this task.”

Images © Hamdia Traoré