Onchocerciasis

2020 Target: Control (elimination in Latin America and Yemen by 2015; elimination in selected countries in Africa by 2020)

Clinical Background: Onchocerciasis, or river blindness, is a black fly-borne parasitic disease of the skin and eyes caused by a filarial worm. When the worms die, they release a symbiotic organism that can destroy eye tissue. The disease causes skin lesions, severe itching and visual impairment, including permanent blindness, and can shorten life expectancy by up to 15 years. It is the second most common infectious cause of blindness, after trachoma.

Epidemiology: An estimated 37 million people worldwide are infected with the pathogen and 90 million people remain at risk. More than 99% of people infected live in 30 endemic countries in Africa. The remainder live in Yemen or several Central and South American countries. Approximately half a million people are visually impaired due to the disease and 270,000 have been blinded.

Burden: Concerted control and elimination programs over the past 40 years have reduced the burden considerably. Since 1995, the African Programme for Onchocerciasis Control (APOC) has treated 90 million people annually in 19 countries, resulting in a 73% case reduction.

Treatment/Prevention Strategy: Preventative chemotherapy with ivermectin (Mectizan, donated by MSD) has been used in elimination and control efforts. Loa loa has also been a barrier to expanding the program in some sites in Africa with lower prevalence of river blindness. Treatment of all infected areas will likely be required to eliminate the disease and achieve the 2020 targets. Ivermectin targets the immature form of the worm, and must be given annually to prevent ongoing transmission until the adult worm dies naturally. Elimination efforts would be helped if a drug to kill the adult form of the worm was developed, which would alleviate the need to annually treat people for river blindness for many years. New drugs safer for to use in Loa loa endemic regions would also be an important advance.

Key Organizations: The Onchocerciasis Control Program, which ran from 1974-2002, helped bring the disease under control in West Africa through vector control. The African Programme for Onchocerciasis Control (APOC), launched in 1995, treats infected populations with ivermectin donated by Merck and targets the disease in primarily East and Central Africa. The Onchocerciasis Elimination Program for the Americas (OEPA) is responsible for controlling the disease in the Americas, also with ivermectin from MSD. The Mectizan Donation Program manages these donations. Several companies are working on a variety of strategies, including working with DNDi, to develop new drugs to treat the adult form of the worms.

Summaries provided by www.UnitingtoCombatNTDs.org

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