WHO’s Dr Maria Rebollo On Eliminating River Blindness

As Lead of the Global Onchocerciasis Elimination Program at the World Health Organization, Dr Maria Rebollo is helping direct the fight against river blindness. With the announcement that Niger has become the first country in Africa to be verified by WHO as having eliminated the disease, she explained how other countries can follow in Niger’s footsteps.

Interview by Jumana Farouky

Fifty years ago, a small fly was devastating villages in Niger. Blackflies carrying the Onchocerca volvulus worm were spreading the disease onchocerciasis – commonly known as river blindness – at a seemingly uncontrollable rate around West Africa. The eye and skin disease causes itching, lesions, impaired vision, and, in some cases, permanent blindness. More than 99% of infected people live in 31 African countries. By the 1970s, in Niger alone, around 60% of people were carrying the parasite.

Today, the disease is on the retreat, with Niger confirmed by WHO as the first African country to have eliminated onchocerciasis. Using a combination of vector control, which involves spraying blackfly breeding areas with larvicide, and treatment with the drug ivermectin, Niger had brought its prevalence rate down to 0.02% by 2002, and declared itself free of the disease in 2021, with the WHO making that victory official in January 2025, on World NTD Day.

Niger’s milestone achievement shows how private nonprofits, pharmaceutical companies, global and local health organizations, and governments can work together to beat river blindness. It also serves as a model for the broader fight against neglected tropical diseases (NTDs). This diverse group of conditions – including onchocerciasis, trachoma, and dengue fever – is estimated to affect more than 1 billion people, mainly in impoverished communities in tropical areas. 

But efforts to end these diseases still get very little investment. “We always say they are the diseases of the neglected people, because it’s not just the diseases that are neglected, it’s also the people affected,” said Dr Maria Rebollo, Lead of the Global Onchocerciasis Elimination Program at WHO and a member of the committee that verified Niger as onchocerciasis-free.

Dr Rebollo, the multi-donor, international Onchocerciasis Control Program helped bring river blindness under control in West Africa, first using vector control and then adding large-scale distribution of ivermectin starting in 1989. How did Niger manage to pull ahead from there to become the first country in Africa to eliminate the disease?

Rebollo: First, Niger has a strong political commitment to achieving elimination, which is very important. Then there are the partnerships with other stakeholders that have supported Niger in its efforts. That has included international groups such as USAID [U.S. Agency for International Development]  and the NTD medicine donation program. Also the Reaching the Last Mile Fund, a $500 million, 10-year grant for 39 countries, including Niger, that helps countries carry out the “last mile” activities of confirming elimination of a disease, such as tracking and recording the necessary data.

WHO also plays a critical role with advocacy, providing guidelines and giving technical support to countries. Because it’s not easy to eliminate a disease. Diseases don’t want to be eliminated. We help with strategy planning, logistics, and documentation and support countries in leveraging opportunities to integrate onchocerciasis treatment with other NTDs. Our NTD Roadmap sets measurable targets for a country’s progress and creates healthy competition between countries.

And we support cross-border collaboration. Diseases pass across borders, but just because two countries are neighbors doesn’t mean they get along. So we help with those conversations. This is one reason we host the Global Onchocerciasis Network for Elimination (GONE) that was launched in 2023. It’s an advocacy network led by the WHO member states and partners that brings all stakeholders together to accelerate progress toward the 2030 elimination target.

We also manage the NTD medicine donation program, which is probably the largest such program in the world. We move billions of tablets across the African continent. In the case of onchocerciasis, that means one treatment a year for every person for about 15 years [the maximum lifespan for a blackfly-transmitted worm]. Merck was the first company to announce an unprecedented medicine donation, saying it will donate ivermectin for as long as needed. And that inspired other companies, such as GSK, Pfizer, and Johnson & Johnson, to donate hundreds of millions of pills over many years. In 2024, Merck celebrated having donated 5 billion ivermectin tablets to cure river blindness.

Niger provides a blueprint for other countries battling river blindness within their own populations. But some countries in Africa will struggle to follow Niger’s example. What are the challenges they face?

Rebollo: For one thing, in several countries their populations are co-infected with another disease called loa loa, and that can cause adverse reactions if you take ivermectin, including encephalopathy [brain damage or dysfunction]. So, it requires a different approach, and we need more investment to identify treatments that can safely eliminate both loa loa and onchocerciasis.

And a more general challenge to eliminating river blindness across Africa is that we can only start treating people from the age of four years old, because we don’t have the medicines to target the youngest children. That is something on the WHO’s priority list, advocating for and working on the development of a pediatric formulation of ivermectin or a new drug that fights onchocerciasis.

One thing the diseases on the NTD list have in common is lack of funding to support research and treatment. Why does so little investment go toward fighting NTDs?

Rebollo: It’s very simple: We know that NTDs don’t really travel. There is no way onchocerciasis is going to create an outbreak in New York, for example, because the vector – the blackfly – is not present there. So, unfortunately, there is that lack of solidarity where we don’t consider fighting NTDs to be as important as diseases that can affect richer regions.

As a result, investments for these diseases are low, even if you consider the millions that are mobilized for NTDs. If a group gives us $100 million over 10 years, it looks like a lot of money. But if you look at the fact that these diseases affect more than 1 billion people per year, it’s not that much.

Senegal is on track to become the second country in Africa to have eliminated river blindness. What other countries are making progress against the disease?

Rebollo: The good news is that, unlike many other diseases, many NTDs can be eliminated. They disappear into history, and we never have to deal with them again. Ten years ago, I was doing surveys in the field in Senegal and there were so many people infected and affected by the disease. Here we are, 10 years later, and the treatment has stopped already, and we are now in the surveillance phase to be able to demonstrate elimination. When you believe you have interrupted transmission of the disease, you need to stop treatment, then do five years of surveillance to make sure it doesn’t re-emerge.

And there are other countries doing well, including Yemen and Nigeria, where they have already stopped treatment in some states. Ethiopia, as well, is doing a pretty good job for being such a large country.

In all of these countries, the governments have really stepped up and the ministries of health own the NTD fight. If governments are the champions of this effort, and then we add medicine donations and critical partners to do some technical support, we can totally win this fight.