From Fascinating to Disturbing — 10 things you should know about onchocerciasis

RTI | Int'l Dev
5 min readDec 17, 2018


By Daniel Cohn and Laura Cane, RTI International

From rock songs to Nobel prizes, onchocerciasis — or oncho — has occasionally had its moment in the spotlight. But the neglected tropical disease (NTD), which affects an estimated 26 million of the world’s poorest and most vulnerable people, isn’t often a focus of major global health discussions. We broke down 10 interesting facts about the disease to help you learn more!

1.Say what? Pronounced ohn-koe-ser-kye-ah-sess, you’ll more often hear the disease referred to as river blindness. The basis of this moniker is quite obvious: Oncho is spread by a type of blackfly that breeds in rapidly flowing streams and it can eventually cause blindness if untreated.

2.An unbearable itch. If repeatedly bitten by infected blackflies, a person may develop an unbearable itch. The itching comes from the inflammatory response to dead or dying microfilariae (think baby worms) that have migrated throughout the body in the skin. Other skin symptoms can include rashes, depigmentation, thinning, and loss of elasticity. Without treatment, the microfilariae can eventually migrate to the eye, and can lead to visual impairment or blindness.

A man in Cameroon shows his legs, which have been affected by onchocerciasis infection. This type of depigmentation is often called “leopard skin,” resulting from a combination of inflammation and scratching to the point that the skin is damaged. Photo Credit: Helen Keller International/Yaobi Zhang

3.And the Nobel goes to… Ivermectin, the medicine used against oncho, was first developed to treat and prevent worms in animals, specifically livestock. It was later found to work on humans. Satoshi Ōmura of Kitasato University in Tokyo and William C. Campbell of the Merck Institute for Therapeutic Research won half of the 2015 Nobel Prize in Physiology or Medicine for discovering the family of medicines from which ivermectin is derived.

4.A dose pole is born. Significant progress against oncho has been led by African organizations, including the Onchocerciasis Control Programme in West Africa (1974–2002) and the African Programme for Onchocerciasis Control (APOC, 1995–2015), initially through vector control and more recently through preventive mass treatment. These programs enabled thousands of community health workers (often volunteers) to distribute the medicine, ivermectin, using a simple measuring stick, called a dose pole, to figure out correct dosing based on height — an alternative to weight, where scales are not available. This was one of the earliest large-scale uses of the dose pole.

A young girl is measured to receive treatment for onchocerciasis and lymphatic filariasis, another neglected tropical disease, at a school in Cross River State, Nigeria. Photo credit: RTI International/Ruth McDowall

5.Enter our friends in Pharma. In 1987, the pharmaceutical company MSD, also known as Merck & Co., Inc., Kenilworth, N.J., U.S.A., committed to donating Mectizan® to help control onchocerciasis. They committed to donate “as much as needed for as long as needed.” Today, this unprecedented drug donation is one of the cornerstones to eliminating the disease and inspired multiple other private sector partners to follow suit.

6.Rock on. When the J.Geils Band released a song called River Blindness in 1981, oncho was a leading cause of blindness in Africa. It remains the second leading infectious cause of blindness worldwide.

“Black flies rise as the water flows

Human kindness — River blindness

Angels cry as the fever grows

Got to face it

Can’t erase it”

Ministry of Health Vector Control Officer, Mr. Ephraim Tukesiga, examines black flies using a temporary field lab in Aura district, Uganda, March 2013 Photo Credit: The Carter Center/E. Staub

7.Yes, fly catching is a thing. To help track progress, teams carry out complex surveys that involve capturing and testing blackflies to determine whether they carry infective larvae. In the past, flies would then be dissected and examined one by one under a microscope; current methods use molecular biology techniques to test pools of up to 200 flies at a time. This painstaking process is critical to ensure the disease is really gone. With partial support from USAID’s ENVISION project, more than 14,165 flies were caught by Uganda’s NTD program last year. So far, of the 6,619 the black flies analyzed, all were negative for O.volvulus — a sign that Uganda’s journey to eliminate the disease is on track.

River blindness experts bait black flies by exposing their bare shins on the banks of the river Nile. Nebbi District of Uganda, March 2013. Photo Credit: The Carter Center/ E.Staub

8.Add this to your list of Dirty Jobs. Fly-catchers use themselves as bait to gather blackflies, capturing them alive — sometimes called the “human landing collection” method. The good news: alternative methods are now being used and further developed which may be more effective in “harvesting” the large number of flies needed for surveys.

“God in His wisdom made the fly,
And then forgot to tell us why.”
— Ogden Nash, American poet

9.Checking off the Americas. The Onchocerciasis Elimination Program for the Americas (OEPA) has assisted ministries of health to successfully eliminate onchocerciasis from Colombia (2013), Ecuador (2014), Mexico (2015), and Guatemala (2016). Their success provides important lessons for other countries working to eliminate the disease worldwide.

10.The elimination of onchocerciasis is now in sight. 2018 has been a year of oncho success stories, with many countries nearing or reaching the point of being able to stop mass treatment, in some cases after more than twenty years. For example, Nigeria and the Carter Center announced in March that Nasarawa and Plateau states will stop distributing medicine for onchocerciasis because transmission has been interrupted. This represents more than 2.6 million people no longer at risk for the disease. In August 2018, Uganda announced that six districts have now reduced oncho transmission to levels where treatment can be stopped. That’s more than 300,000 people no longer worrying about the disease. At RTI, we have been proud to support both countries in their oncho elimination journeys through USAID’s ENVISION Project, together with partners.

Join us in spreading the word about onchocerciasis and the incredible progress toward elimination! As part of a global movement, we are raising our voice to ensure onchocerciasis elimination is prioritized. With continued support, we believe elimination is achievable and will have long-lasting impacts on the health of many of the world’s poorest people.



RTI | Int'l Dev

RTI's #globaldev team applies science and knowledge to improve lives in developing countries around the world. An official RTI International feed.