­Visceral leishmaniasis and control measures in an endemic urban area: space-temporal bayesian analysis

Abstract

Background Visceral leishmaniasis is an important but neglected disease that is spreading and is highly lethal when left untreated. This study sought to measure the Leishmania infantum seroprevalence in dogs, the coverage of its control activities (identification of the canine reservoir by serological survey, dog culling and insecticide spraying) and to evaluate its relationship with the occurrence of the disease in humans in the municipalities of Araçatuba and Birigui, state of São Paulo, Brazil. Methods Information from 2006 to 2015 was georeferenced for each municipality and modeling were performed for the two municipalities together. To do this, latent Gaussian Bayesian models with the incorporation of a space-time structure and Poisson distribution were used. The Besag-York-Mollie models were applied for random spatial effects, as also were autoregressive models of order 1 for random temporal effects. The modeling was performed using the INLA (Integrated Nested Laplace Approximations) deterministic approach, considering both the numbers of cases as well as the coverage paired year by year and lagged at one and two years. Results Control activity coverage was observed to be generally low. The behavior of the temporal tendency in the human disease presented distinct patterns in the two municipalities, however, in both the tendency was to decline. The canine serological survey presented as a protective factor only in the two-year lag model. Conclusions The canine serological survey coverage, even at low intensity, carried out jointly with the culling of the positive dogs, was associated with a decrease in the occurrence of the disease in humans, the effects of which would be seen two years after it was carried out.