In African countries like Chad, Ghana, Malawi, and South Sudan, the bite of an infected blackfly transmits the parasitic infection onchocerciasis – better known as river blindness because the fly breeds near fast flowing rivers. Many of those who are infected have no idea until the adult worms have mated and produced juvenile parasites. Symptoms don’t appear until the larvae migrate through the body, causing severe itching, visual impairment, and, if the disease is left untreated, blindness. An estimated 21 million people are infected with river blindness worldwide. More than a million people have lost their sight from this disease (WHO).

Yao Sodahlon, MD, MSc was one of the lucky ones. When he was 15 years old, medical staff at the high school he attended in Togo tested him for river blindness and discovered that he was infected. “I received the treatment that was available at the time, and I was cured,” he says. “The good thing is, because I was no longer living in an endemic area, my risk of being re-infected was very low.”

Geography proved fortunate in Sodahlon’s case. The village next to his, which sat alongside a river, was decimated by onchocerciasis. “It was well known that if you live there, you become blind,” Sodahlon says. “River villages are fertile – they can grow a lot of crops. People started deserting these communities because of river blindness, leading to a loss of productivity and poverty.”

A Calling in Public Health

After graduating from the University of Lomé medical school in Togo, Sodahlon had two choices: become a pediatrician or a tropical disease specialist. Drawing from his personal experience, he chose the latter. From 1996 to 2006, he worked for the Togo Ministry of Health, helping to control the spread of tropical diseases like malaria, river blindness, and lymphatic filariasis (LF, also known as elephantiasis) – a disfiguring parasitic disease that spreads in the same regions as river blindness.

In 1987, Merck & Co., Inc., Kenilworth, N.J., U.S.A.,* made the landmark decision to donate the drug, Mectizan^® (ivermectin), to combat river blindness. They chose The Task Force for Global Health as home to the Mectizan^® Donation Program (MDP) secretariat which ended up supplying Sodahlon with the medicine he needed to protect his country’s residents from this tropical disease. “That’s how I got to know the team here,” he says.

In 1998, Merck & Co., Inc., Kenilworth, N.J., U.S.A expanded MDP’s mandate to include the donation of Mectizan^® for LF elimination. In 2006, Dr. Sodahlon was recruited to join MDP to serve as medical officer and lead MDP’s LF elimination program. Ten years later, he took over as the program’s director.

Getting Drugs to Countries in Need

The centerpiece of MDP is the anti-parasitic drug Mectizan^® (ivermectin), which kills worm larvae and stops river blindness from progressing. The drug has been so effective that the global goal has changed from control of the disease to elimination of the disease worldwide – which would be a remarkable achievement. Mectizan^® is also co-administered with another anti-parasitic drug called albendazole, donated by GlaxoSmithKline (GSK), for LF elimination in most African countries. In countries where there is no river blindness, Mectizan^® is donated to facilitate the implementation of a new elimination strategy using “triple therapy” which co-administers ivermectin, albendazole, and diethylcarbamazine (DEC, donated by Eisai) to accelerate LF elimination. 

Sodahlon leads the MDP team to ensure that Mectizan^® gets to its target countries on time and is effectively and safely distributed. At least 65 percent of people within any given community must receive it to eliminate transmission of the parasite. Safety is key. “We need to ensure that when people are taking the medicine, there are no severe adverse events,” he says. “The people who are distributing the drugs are trained to watch their community after treatment and to report any side effects that do occur.”

Another important aspect of Sodahlon’s job is to work with the ministries of health in each country to ensure they are committed to funding and implementing the drug distribution program. “If I identify any funding gaps, I lobby for that country so additional money is mobilized,” he says.

Challenges and Success Stories

Last year, more than 300 million doses of Mectizan^® were donated. “That’s the most successful part of the program – making sure that people who need the medicine can get it for free,” says Sodahlon.

However, ensuring that everyone who needs the drug receives it remains a challenge. First, countries must identify all the communities that need treatment by mapping the disease. That is not easy, given that symptoms are not always apparent early on. In addition, once countries determine which areas could benefit from Mectizan^®, wars and other instability in these developing nations can keep the drug from the people who need it most.

Despite these roadblocks, MDP has already begun to see the impact of its efforts. Four countries in Latin America – Colombia, Ecuador, Guatemala, and Mexico – are now free from river blindness. The World Health Organization (WHO) verified the disease has been eliminated within those countries. “The burden of this disease is going down,” Sodahlon says. “In Africa, for instance, it’s not common anymore to see people going blind because of river blindness. What happened in Latin America demonstrates the concept that this disease can be eliminated.”

In 2017, WHO pronounced Sodahlon’s home country free from LF. “That has been one of our program’s greatest successes,” he says. “We are optimistic that both diseases can and will be eliminated.”

*Merck is known as MSD outside the United States and Canada