Claims of a "major breakthrough" in the battle to eliminate river blindness need to be treated with caution, according to a specialist.
William David Taylor, coordinator of the Sustainable Control of Onchocerciasis Today and Tomorrow programme and a professor at the University of Edinburgh, United Kingdom, says that a study published in PLoS Neglected Tropical Diseases in July showing that long-term ivermectin treatment can halt the disease is not applicable everywhere.
Researchers, led by Hans Remme, former research coordinator at the WHO Special Programme for Research and Training in Tropical Diseases, showed that 15–17 years of annual or six-monthly treatment with ivermectin treated almost all river blindness infections in three areas of Mali and Senegal.
Remme told SciDev.Net: "This study has provided the first evidence that the parasite and transmission can be eliminated, and that treatment can be safely stopped after a long period of ivermectin treatment. This is a major breakthrough for onchocerciasis control that has far-reaching implications for the fight against this disease."
River blindness, or onchocerciasisis, an eye and skin disease, caused by the filarial worm Onchocerca volvulus and spread by infected blackflies that breed in rivers. Over 37 million people are infected, mostly in poor, rural African communities.
But Taylor says that "while ivermectin may, in certain circumstances, interrupt transmission of onchocerciasis, it is generally agreed that alone it is unlikely to do so over a vast majority of areas where onchocerciasis is endemic".
"Furthermore, in those areas where O. volvulus and Loa loa [another nematode] are co-endemic, ivermectin must be used with caution because of the risk of severe adverse reactions following death of L. loa microfilariae."
This means that use of ivermectin alone to stop transmission is unrealistic, "especially if it requires annual treatment for 17 years".
Taylor also pointed to increasing evidence of ivermectin resistance and says that his team is instead working on a vaccine.
Morad Ahmed Morad, a professor of medicine at Tanta University, Egypt, welcomed the new research findings, but says the work "only presents the first step in the long and hard battle for kicking river blindness out of Africa, as well as ending it as a public health threat and a socioeconomic problem".
PLoS Neglected Tropical Diseases 3, e497 (2009)