Over 37 million people, mostly in poor, rural African communities are infected with onchocerciasis, which is often called river blindness because the blackfly which transmits the disease breeds in rivers. Blindness is the most debilitating symptom of this public health threat which also causes skin disease.

Published today in the open-access journal PLoS Neglected Tropical Diseases are the results of a study showing that treatment with ivermectin stopped further infections and transmission in three specific areas of Mali and Senegal where the disease has been endemic.

Previously, it was thought that elimination of river blindness was only possible in the limited, isolated areas in the Americas where the disease is endemic, according to a news release issued by the UN World Health Organization (WHO), which collaborated with the health ministries of the two countries in carrying out the study.

“This evidence is an historic milestone - it has far-reaching implications for the fight against this disease. Prior to this study we did not know if we would ever be able to stop treatment,” said Uche Amazigo, the Director of the African Programme for Onchocerciasis Control (APOC).

APOC is charged with implementing control of the disease across Africa, where more than 99 per cent of cases are found.

Merck & Co., Inc. - the company that discovered and manufactures ivermectin - agreed in 1987 to donate the drug free of charge to countries where river blindness is endemic, resulting in the treatment of over 60 million people in 26 African countries in 2008.

While this enabled the control of river blindness in Africa, it has not been clear whether it could also be used to eliminate infection and transmission to the extent that treatment with ivermectin could be safely stopped, said WHO.

The agency noted that ivermectin kills the larvae but not the adult worms of Onchocerca volvulus, the parasite that causes the disease, so annual or biannual treatments are required to prevent resurgence.

The study shows that after 15 to 17 years of six monthly or annual treatments, only a few infections remained in the human population.

“Transmission levels were below predicted thresholds for elimination, so treatment was subsequently stopped in test areas and follow-up evaluations after 1.5 to two years showed that no further infections or transmission occurred,” stated WHO.

“Although further studies are needed to determine to what extent these findings can be extrapolated to other areas in Africa, the principle of onchocerciasis elimination with ivermectin treatment has been established,” it added.

Earlier this month, WHO announced the launch of a clinical trial in three African countries for the drug moxidectin, which is being investigated for its potential to kill or sterilize the adult worms of the parasite that causes river blindness.

If moxidectin kills not only the larvae but also sterilizes or kills the adult worms, it has the potential to interrupt the disease transmission cycle within around six annual rounds of treatment, according to WHO.

The development of the drug is being conducted through a collaboration of the Special Programme for Research and Training in Tropical Diseases, which is executed by WHO and Wyeth Pharmaceuticals.

The trial involves 1,500 people in Ghana, Liberia and the Democratic Republic of the Congo (DRC), and will take place over the next two and a half years.#