River Blindness

What Is River Blindness? A debilitating human disease caused by small thread-like nematodes (roundworms) and spread by black flies.

Symptoms: Intense itching, various skin rashes and blindness. One such rash is known as “leopard skin.”

Can It Be Eradicated? River blindness is not currently eradicable, but because the worms infect only humans, the disease can be eliminated in certain regions through annual or semi-annual treatment with the drug ivermectin.

Status: Nearly eliminated in the Americas; on track for ELIMINATION in many parts of Africa.

Treating the Community

World map with countries with cases of river blindness in 2015 in one color and areas of transmission in Brazil and Venezuela in another color.
Today, 99% of river blindness cases occur in Africa. In the Americas, transmission has been stopped in Colombia, Ecuador, Mexico and Guatemala, and occurs only in small, isolated areas of Venezuela and Brazil.
© AMNH

Countless rivers and streams nourish the fertile valleys of Africa and Latin America. These waterways are a source of life. But they can also be a breeding ground for black flies that transmit river blindness. When infected black flies bite people, they can pass along small thread-like parasites, which mate and send thousands of tiny larvae into the skin and eyes—causing extreme itching, skin rashes and in the worst cases, blindness.

One hundred twenty million people are currently at risk for river blindness worldwide. But through education, surveillance, and community-based drug treatment, the disease has been nearly eliminated in Latin America. Although elimination—removing the infecting agent from a particular location—was once considered impossible in Africa, many believe that goal is now achievable in some areas. Global eradication may even be possible someday.

A graphic depicting the transmission cycle of river blindness from infection via black fly and another black fly biting an infected person and spreading the disease.
© AMNH

Latin America — Making Progress

A young person with a dark bowl cut, a stick through their nose and facial decoration on the chin, and an elaborate beaded necklace.
Working with Remote Populations. Venezuela, 2013 | River blindness remains a problem among the Yanomami, who live in small, semi-permanent villages in the Amazon rainforest near the border between Brazil and Venezuela. The Carter Center works closely with the Pan American Health Organization and Brazilian and Venezuelan health officials to root out the last cases of river blindness.
CAICET Venezuela/Oscar Noya-Alarcon

River blindness (also called onchocerciasis) once threatened half-a-million people in Latin America with blindness and skin disease. Today, the illness is found only in remote populations near the border between Brazil and Venezuela. Soon, it is hoped, even those populations will no longer know the disease. How have health workers managed to stop transmission? Mainly with the drug ivermectin. The medicine kills the prelarval worms, or microfilariae, that move through the victim’s skin and eyes. 

With the microfilariae dead, the black flies can’t transmit the infection from one person to another. A dose of ivermectin twice per year is usually enough to stop transmission. Typically, local volunteers are responsible for administering ivermectin to their entire community. This practice, called mass drug administration or MDA, has proven highly successful, enabling local populations to take ownership of their own treatment.

Africa — Unique Challenges

A laboratory technician stands at a counter beside a sink wearing plastic gloves and works to put something in a small circular bowl.
Laboratory Technician Monica Ngabirano. Uganda, 2012 | At a lab in Kampala, Uganda’s capital city, workers test black flies—as well as human blood and skin tissue samples—for evidence of river blindness infection. This information helps them map progress toward eliminating the disease.
The Carter Center/Kay Hinton

In Africa, health officials have generally sought to control river blindness—to keep the number of cases to a minimal level. But the success of semiannual mass drug administration in Latin America has raised hopes that the disease can be eliminated—that is, removed completely—from some African countries as well. Still, challenges remain.

 River blindness is much more prevalent in Africa than it ever was in Latin America, and African black flies are more efficient at transmitting the parasite among humans. Population migrations, weak health systems, political instability and the long flight range of African black flies present challenges as well.

A child leads a blind adult using a long stick which they both grip as they walk past two huts. Child Leading a Blind Adult. Nigeria, 2010 | Blindness from the disease frequently strikes adults in their most productive years. Often the entire community—young and old—feels the strain, as children are called into service to lead and assist the blind.
Mectizan Donation Program/Peter DiCampo
A child holds two pills in their palm and holds a plastic cup in the other, with three more children of varying ages sitting or standing behind them. A Child Receiving Ivermectin Treatment. Nigeria, 2014 | In each affected community, it’s the job of dedicated volunteers to distribute ivermectin once or twice a year. To be effective, drug administration must reach at least 85% of those medically eligible to take the tablets—even those showing no signs of the disease. Treatment must continue for several years until the mature worms have died.
The Carter Center/Tom Saater