Evidence of zero <i>Onchocerca volvulus</i> infectivity among populations living in first-line communities to the Arinta and Erin-Ijesha waterfalls, Southwest Nigeria

Recent breeding site assessments of rivers revealed that blackflies are actively biting at the Erin-Ijesha and Arinta waterfalls in Southwest Nigeria, predisposing nearby first-line communities to heightened risk of onchocerciasis transmission. This observation necessitated an evaluation of onchocerciasis transmission in nearby sentinel communities to determine the prevalence of Onchocerca volvulus infectivity and determine whether current treatment strategies should be modified or intensified. The cross-sectional study was conducted between October 2024 and November 2024 in Ipole-Iloro and Erin-Ijesha, first-line communities nearest to the Arinta and Erin-Ijesha waterfall respectively. Following the established gold standard technique for monitoring and evaluating onchocerciasis, skin snips were collected from the right and left iliac crests of 236 individuals aged 10 years and above and are residents of the communities for more than 5 years. Onchocerca infectivity was assessed using microscopy and the O-150 Polymerase Chain Reaction (PCR) technique. Results from both microscopy and PCR assay showed that all skin snips were negative for O. volvulus parasite, indicating no active transmission. Given the high-risk status of these communities, these findings suggest the possible absence of ongoing transmission and further highlights the effectiveness of ongoing mass drug administration (MDA) in driving the elimination of onchocerciasis.