Onchocerciasis (River Blindness)
Causative Agent: Onchocerca volvulus (parasitic worm)
Transmission: Repeated bites of infected blackflies that breed in rapidly flowing rivers
A Leading Cause of Preventable Blindness
Onchocerciasis can cause severe itching, disfiguring skin conditions, and permanent blindness if left untreated
Key Statistics
249.5M
People requiring treatment (2023)
14.6M
With skin disease
1.15M
With vision loss
5
Countries verified as free
About Onchocerciasis
Onchocerciasis, commonly known as "river blindness," is a parasitic disease caused by infection with the worm Onchocerca volvulus. The disease causes severe itching, disfiguring skin conditions and visual impairment, and can result in permanent blindness.
The parasite is spread and transmitted to humans by the repeated bites of infected blackflies that breed in rapidly flowing rivers, which is why the disease is often called "river blindness." More than 99% of infected people live in Africa and Yemen, with the remaining 1% living on the border between Brazil and Venezuela.
Symptoms and Impact
The symptoms of onchocerciasis include severe itching, disfiguring skin conditions, and visual impairment that can progress to permanent blindness. The Global Burden of Disease Study estimated in 2017 that 14.6 million of the infected people already had skin disease and 1.15 million had vision loss.
Progress Toward Elimination
Five countries have been verified by WHO as free of onchocerciasis after successfully implementing elimination activities for decades: four in the region of the Americas (Colombia, Ecuador, Mexico, and Guatemala), and one in Africa (Niger). In 2022, Senegal stopped treatment and is now under post-treatment surveillance.
Several countries have stopped mass drug administration (MDA) in at least one focus, including Equatorial Guinea, Ethiopia, Mali, Nigeria, Sudan, Tanzania, Togo, Uganda, and Venezuela. Globally, 1.8 million people live in areas that no longer require MDA for onchocerciasis.
Global Distribution
In 2023, at least 249.5 million people required preventive treatment against onchocerciasis. The disease is predominantly found in:
- •Africa (more than 99% of cases)
- •Yemen
- •Brazil-Venezuela border region
Countries Verified as Free
- ✓Colombia (2013)
- ✓Ecuador (2014)
- ✓Mexico (2015)
- ✓Guatemala (2016)
- ✓Niger (2025)
AM2NTD's Work
AM2NTD is developing mathematical models to better understand onchocerciasis transmission dynamics and optimize control strategies in endemic African countries.
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