Epidemiological surveillance of neglected tropical diseases in silent areas: the case of zoonotic sporotrichosis

Abstract A common practice in the analysis of the spatial distribution of neglected tropical diseases is to assume that in silent areas (no reports) there are no cases. However, when the problem is underreporting, it risks reinforcing the neglect of areas that should be a priority. Instead of this assumption, one can predict the number of cases in silent areas using epidemiologic and spatial dependence information. The present study exemplifies this approach, using the integrated nested Laplace approximation in Bayesian spatial models that relate social vulnerability and the number of reported cases of feline (zoonotic) sporotrichosis in census tracts (CTs) of the municipality of Guarulhos. In addition to predictions for silent CTs, we assigned a priority index to all CTs. The results showed a more problematic epidemiologic situation, compared to the scenario in which it is assumed that there are no cases in silent CTs. To iteratively validate the index predictions and calibrate the degree of confidence assigned to the predictions, one can compare the distribution of the priority indices of silent CTs with the distribution of cases identified through active surveillance in a sample of silent CTs.