Onchocerciasis is an infection caused by the nematode Onchocerca volvulus. Humans acquire onchocerciasis through the bite of Simulium black flies.
Because the fly develops and breeds in flowing water, onchocerciasis is commonly found along rivers and is sometimes referred to as river blindness.
Onchocerciasis is not acquired in the United States. Occasional cases are found in immigrants or travelers from endemic areas. However, symptomatic onchocerciasis usually requires heavy infestations and repeated exposure to the vector fly. Short-term travelers are at little or no risk of the disease. Pruritus, dermatitis, and eosinophilia may occur in travelers who stay longer than 3 months in endemic areas of Africa. Symptoms may occur months to years after leaving the endemic area.
Currently, onchocerciasis is endemic to 30 African countries, Yemen, and in localized foci of 6 Central and South America countries. Globally, approximately 18-36 million individuals have onchocerciasis, 99% of whom reside in Africa. The World Health Organization (WHO) estimates that 750,000 people are blind or have reduced vision as a result of the disease.
Seriousness of this Disease
The symptoms shown for this disease differ from area to area – In forested areas the virus erupts as skin disease , while blindness is more common in savanna areas ( rolling grassland scattered with shrubs and isolated trees). Children born to mothers with Onchocerciasis may be immune tolerant.
Countries that are affected by Onchocerciasis:
Tropical areas in the following countries are prone to Onchocerciasis. All these affected areas are from 31 countries in sub-Saharan Africa
Angola, Benin, Burkina Faso, Burundi, Cameroon, Central African Republic, Chad, Republic of Congo, Côte d’Ivoire, Democratic Republic of the Congo, Equatorial Guinea, Ethiopia, Gabon, Ghana, Guinea, Guinea-Bissau, Kenya, Liberia, Malawi, Mali, Mozambique, Niger, Nigeria, Rwanda, Senegal, Sierra Leone, South Sudan, Sudan, Togo, Uganda, United Republic of Tanzania. It has also been introduced in Yemen.