Human onchocerciasis: current assessment of the disease burden in Nigeria by rapid epidemiological mapping

Abstract

Rapid epidemiological mapping of onchocerciasis (REMO) was carried out in Nigeria between 1994 and 1996, to provide accurate estimates of the populations living in high-risk areas for the disease and to identify the communities to be given priority treatment with Mectizan (ivermectin, MSD). The rapid epidemiological assessment (REA) teams which carried out the survey comprised epidemiologists, geographers, and entomologists. They used topographical maps, at a scale of 1:250 000, to select sample villages at 30-km intervals along selected river courses. Several non-governmental development organizations participated in the surveys, providing support to the teams.In each study community, 50 adult males who had lived in the area for at least 10 years were randomly selected and examined for the presence of palpable, onchocercal nodules. The REA results were cross-validated by an independent REMO expert and then presented, initially as percentage prevalences in pie-chart form, using a geographical information system. The number of Nigerians living in high-risk areas (demarcated by river systems with villages that had ≥ 19% prevalence) and who therefore require urgent Mectizan treatment, was estimated as 13 809 313. The national REMO map produced is allowing the African Programme for Onchocerciasis Control's technical consultative committee to prioritize the approval of proposals submitted from Nigeria in a rational and effective manner.