Mapping and prediction of schistosomiasis in Nigeria using compiled survey data and Bayesian geospatial modelling

Schistosomiasis prevalence data for Nigeria were extracted from peer-reviewed journals and reports, geo-referenced and collated in a nationwide geographical information system database for the generation of point prevalence maps. This exercise revealed that the disease is endemic in 35 of the country’s 36 states, including the federal capital territory of Abuja.

Schistosoma haematobium, the predominant species in Nigeria, was found across 31 states, S. mansoni across 22 states and S. intercalatum in two states. The estimated prevalence of S. haematobium, based on Bayesian geospatial predictive modelling with a set of bioclimatic variables, ranged from 0.2% to 75% with a mean prevalence of 23% for the country as a whole (95% confidence interval (CI): 22.8-23.1%). The model suggests that the mean temperature, annual precipitation and soil acidity significantly influence the spatial distribution. It was estimated that 11.3 million children require praziquantel annually (95% CI: 10.3-12.2 million).