The spatial distribution of Schistosoma mansoni infection in four regions of western Côte d’Ivoire

Abstract

Schistosomiasis poses a considerable public health burden in sub- Saharan Africa and a sound understanding of the spatial distribution facilitates to better target control interventions. The objectives of this study were i) to assess the prevalence of <em>Schistosoma mansoni</em> among school-aged children in four regions of western Côte d’Ivoire; ii) to determine demographic, climatic and environmental factors that influence the distribution of <em>S. mansoni</em>; and iii) to map and predict the distribution of S. mansoni in non-sampled locations. Parasitological surveys were carried out in 264 schools from June to December 2011. In each school, we aimed to examine 50 children for <em>S. mansoni</em> infection using duplicate Kato-Katz thick smears. Schools were georeferenced using a hand-held global positioning system receiver. Demographic data were obtained from readily available school lists, while climatic and environmental data were extracted from open-access remote sensing databases. Multivariable, binary non-spatial models and a Bayesian geostatistical logistic regression model were used to identify demographic, climatic and environmental risk factors for S. mansoni infection. Risk maps were developed based on observed <em>S. mansoni</em> prevalences and using Bayesian geostatistical models to predict prevalences at non-sampled locations. Overall, 12,462 children provided a sufficiently large stool sample to perform at least one Kato-Katz thick smear. The observed overall prevalence of S. mansoni infection was 39.9%, ranging from 0 to 100% at the unit of the school. Bayesian geostatistical analysis revealed that age, sex, altitude and difference between land surface temperature at day and night were significantly associated with <em>S. mansoni</em> infection. The <em>S. mansoni</em> risk map presented here is being been used by the national schistosomiasis control programme for spatial targeting of praziquantel and other interventions.