Spatial Epidemiology of Malaria Incidence and Environmental Risk Factors in Ogun State

Malaria remains the leading cause of morbidity and mortality in Nigeria's South West geopolitical zone, and spatially disaggregated understanding of the environmental determinants of transmission intensity is essential for targeting vector control and case management resources with precision in Ogun State. This study conducts a spatial epidemiological analysis of malaria incidence and its environmental risk factors across Ogun State using a multi-data source approach. Malaria case data from 84 primary healthcare facilities across 20 local government areas for 2021 to 2023 were obtained from the Ogun State Health Management Information System and standardised to ward-level incidence rates. Environmental predictor variables derived from satellite imagery and spatial datasets included NDVI, proximity to water bodies, land surface temperature, rainfall accumulation from CHIRPS, and elevation from SRTM. Spatial autocorrelation analysis identified malaria transmission clusters, while Bayesian spatial regression modelling with conditional autoregressive priors was applied to estimate covariate-adjusted associations. Results identify statistically significant malaria hotspots in riverine LGAs including Yewa South, Obafemi Owode, and Ifo, where proximity to stagnant water bodies and high NDVI in degraded forest zones create optimal anopheline mosquito breeding conditions. Bayesian regression confirms elevation above 250 metres and distance from water bodies as significant protective factors, while NDVI and seasonal rainfall accumulation are positive predictors of incidence. The study applies Bayesian spatial modelling methods not previously used in Ogun State malaria research, providing statistically robust estimates of environmental risk contributions. Recommendations include targeted insecticide-treated net distribution and larval source management in identified hotspot wards. Keywords: malaria, spatial epidemiology, environmental risk, Ogun State, South West Nigeria.