Eco-Epidemiological Determinants of Onchocerciasis Persistence in Post-Control Communities in Benue State, North Central Nigeria: A Complex Systems Analysis

Despite decades of community-directed treatment with ivermectin, onchocerciasis transmission persists in certain Benue State communities, suggesting that eco-epidemiological factors beyond drug delivery failure contribute to residual transmission and challenging the conceptual basis of current control strategies. This doctoral research investigates eco-epidemiological determinants of onchocerciasis persistence using a complex systems analytical framework in post-control communities in Benue State, North Central Nigeria. A longitudinal mixed-methods study was designed across 12 communities in Makurdi, Agatu, and Oju Local Government Areas with documented treatment histories of more than 15 annual rounds. Annual entomological and parasitological surveys over three years measured Simulium damnosum biting rates and infectivity, community microfilarial loads, and skin snip positivity. High-resolution satellite-derived hydrological variables including river flow velocity, turbulence, dissolved oxygen levels, and seasonal flood extent were modelled as predictors of black fly breeding density. Community-level therapeutic coverage data, population mobility indices from mobile phone data, and vector insecticide susceptibility profiles were integrated into a system dynamics model. Recent evidence from 2020 to 2024 points to hydrological intensification, cross-border human movement, and subtherapeutic coverage in mobile populations as understudied drivers of transmission persistence. The framework proposed provides a novel analytical lens for guiding post-control verification assessments. Findings will be submitted to the Benue State NTD Programme and the WHO African Programme for Onchocerciasis Control. Keywords: onchocerciasis persistence, eco-epidemiology, complex systems, Benue State, post-control communities.