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21 July 2009
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|Logo of the World Health Organization at WHO headquarters in Geneva|
Onchocerciasis, or river blindness, is transmitted by the black fly, which breeds in rivers. It is a major cause of blindness and also causes debilitating skin disease. The disease flourishes in poor, rural communities in west and central Africa.
River Blindness has been treated with a drug called Ivermectin for more than 20 years. The drug, which has been provided free of charge by Merck & Co., successfully stops further infections and transmission of this parasitic disease.
But the World Health Organization notes Ivermectin only kills the larvae, not the adult worms, which cause the disease. Therefore, it says annual or biannual treatments must be given to people living in vulnerable African communities to keep the disease in check.
Results of a two-year study in Senegal and Mali show it is possible to stop Ivermectin after many years of treatment without provoking further infections and transmission. Dr. Hans Remme is overall coordinator of the study, which was carried out by WHO and numerous partners.
"We actually tested this hypothesis that you could eliminate the parasite and transmission and safely stop treatment," Dr. Remme said. "And, we tested it by actually stopping treatment in five to eight villages in each of the study areas. And, then we followed the population up very intensely for two years. And, the very good news, which is published in this article is that over those two years, we did not find any infected people in those test areas and we did not find any infected black flies and a lot of them were analyzed. Over 150,000 flies were analyzed annually. So this is based on very large data."
Dr. Remme calls the study a milestone. He says further studies are needed to determine to what extent these findings can be extrapolated to other areas in Africa. But, he says, the principle of onchocerciasis elimination with Ivermectin treatment has been established.
"It is the first time then that we now can say, "Yes." It takes a long time, but ultimately you can anticipate elimination of Onchocerciasis, not only as a public health problem, but of the parasite and transmission and therefore we can safely stop treatment," Dr. Remme said.
Dr. Remme says researchers are trying to develop a better drug, which would kill or completely sterilize the adult worm. Such a drug, he says could eliminate river blindness within six, rather than 15 years.
He says a very promising drug, called Moxydectin and manufactured by Wyatt, is currently undergoing trials in the Democratic Republic of Congo, Liberia and Ghana. He says results of these trials should be known by 2012.