Maintaining compliance to ivermectin in communities in two West African countries

We have investigated various aspects related to managing wide-scale ivermectin distribution schemes within randomized controlled trials in communities where onchocerciasis is endemic. Multiple logistic regression analysis of determinants of compliance to five doses of ivermectin in 589 people in Sierra Leone showed independent significant associations with leopard skin depigmentation, the severity of side effects of treatment, fulfilling the exclusion criteria for treatment, and long-term residence in the community. These results are useful for tailoring health promotion messages in Sierra Leone, but the associations may differ in other West African societies. In Nigeria 1847 people were interviewed about various subjective responses, including itching. None of these showed clear improvement after three years of ivermectin treatment. Positive comments about treatment were generally non-specific and similar in the placebo and ivermectin groups. Negative comments were usually related to adverse reactions, especially itching and rash, and were more common after ivermectin. The lack of any benefit attributable to ivermectin that is discernible to its recipients may make it difficult to maintain the high compliance rates needed for long periods if mass dosing programmes are to have a lasting impact on onchocerciasis. In addition, no consistent effects of ivermectin were found by measuring visual acuity, height, weight or haematocrit in comparison with placebo. This may indicate that evidence of clinical impact is very slow to develop and is hard to measure using simple objective methods after only three doses of treatment. At present it seems that parasitological, entomological and detailed ophthalmological or dermatological methods are required to demonstrate the impact of ivermectin treatment in the medium-term.