Onchocerca volvulus infection prevalence and intensity in Logo and Nyarambe Health Zones in Ituri, Democratic Republic of the Congo in 2010 and in 2021–2023: results of screening for clinical trials of moxidectin versus ivermectin

Given that the reduction in infection prevalence and intensity in Logo HZ cannot be attributed to ivermectin distribution, it has to be due to reduction in infective vector biting rates, possibly linked to a recently proposed change in vector species triggered by land-use changes. Because SmfD reflects transmission events approximately 2-15 years earlier, infective vector biting rate assessment is needed to determine current transmission rates. Reduced transmission shifts macrofilariae age distribution toward older macrofilariae with lower reproductive capacity. Comparison of the results from the Phase 3 and the ongoing efficacy study might help determine whether drug susceptibility changes significantly with macrofilariae age. Should that be the case, transmission models evaluating the impact of mass drug administrations could be adjusted.