Schematic of the Bayesian model.

The model is comprised of three components reflecting the different possible combinations of available data at each location: i) schools for which only questionnaire and environmental data are available and used to inform the parameters governing the relationship between the two (step 1); ii) schools which have both questionnaire and parasitology are used to inform the relationship between the proportion of children reporting blood in urine and the prevalence of S. haematobium (step 2); iii) schools at which only parasitology and covariate data are available are used to further inform the model by identifying parameters values of steps 1 and 2 that best explain the link between environmental covariates and infection prevalence. Within the Bayesian framework, these three components are solved simultaneously, making it possible to find the parameter values for steps 1 and 2 that best fit all available data.