Director, Mectizan® Donation Program
Yao Sodahlon – River Blindness and Lymphatic Filariasis
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 (elephantiasis) – a disfiguring parasitic disease that spreads in the same regions as river blindness.
In 1987, Merck & Co., Inc.* made the landmark decision to donate a safer drug, Mectizan® (ivermectin), to combat river blindness. They chose The Task Force for Global Health as home to the Mectizan® Donation Program (MDP) secretariat because of its wealth of expertise in getting medicines to those most in need. MDP supplied Sodahlon with many of the medicines he needed to protect his country’s residents from tropical diseases. “That’s how I got to know the team here,” he says.
In 1998, Merck expanded MDP’s mandate to include the donation of Mectizan® for lymphatic filariasis elimination. In 2006, Dr. Sodahlon was recruited to join MDP to serve as medical officer and lead the MDP’s lymphatic filariasis elimination program. Ten years later, he took over as the program’s director.
Getting Drugs to Countries in Need
The centerpiece of the program Sodahlon runs is the anti-parasitic drug Mectizan® (ivermectin), which kills worm larvae and stops river blindness symptoms from progressing. The drug has been so effective, that the global goal has changed from control of the disease to elimination of transmission worldwide – a remarkable achievement. Mectizan® works alone for river blindness elimination. For LF, it is combined with albendazole (donated by GSK) to eliminate LF in most of Africa. In countries where river blindness is not present, Mectizan® and albendazole are co-administered with diethylcarbamazine (DEC, donated by Eisai) to eliminate lymphatic filariasis.
Sodahlon’s job is 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 also 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.”
The second part 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.
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 isn’t easy, given that symptoms aren’t always apparent early on. Even once they 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. World Health Organization (WHO) verified that the disease has been eliminated. “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, the World Health Organization pronounced Sodahlon’s home country free from lymphatic filariasis. “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