Ivermectin does not reduce the burden of itching in an onchocerciasis endemic community

Degrees of itching were estimated before and for 6 months after a fourth dose of ivermectin or placebo was given to 97 subjects in Sierra Leone. There was no reduction in itching attributable to ivermectin at any stage, but there were non-significant increases in the prevalence, severity and localization of itching within the first 2 months after ivermectin compared to placebo. We also found that cell-mediated immune responses to Onchocerca volvulus were significantly increased 4 weeks after a single dose of ivermectin compared to before treatment. A temporary reversal of the state of immunosuppression in people with onchocerciasis may counterbalance the reduction in skin microfilarial loads following ivermectin, with no consequent reduction in itching. The lack of effect of ivermectin on itching, a major symptom of onchocerciasis, while disappointing, need not detract from the success of mass distribution programmes.