Location of Onchocerciasis
Onchocerciasis is particular to a certain region of the world. All infections caused by the worm Onchocerca volvulus are reported in tropical climates, with almost 90% of documented Onchocerciasis cases occurring in sub-Saharan Africa. Today it is estimated that 30 countries in Africa are at risk of the disease, these including Chad, Ethiopia, Nigeria, Sudan and Tanzania. As the blackflies that carry the parasite breed in fast-flowing rivers and streams, those living in remote villages located near fertile land where people rely on agriculture and water systems are most susceptible to the disease. The other 10% of cases documented occur in the isolated areas of South and Central America such as Brazil, Columbia, Mexico and Guatemala as well as Yemen in the Middle East. It is thought the disease was spread to these areas through slave trade.
Map showing countries affected by River Blindness