Impact of the household environment risk for maintenance of natural foci ofLeishmania infantumtransmission to human and animal hosts in endemic areas for visceral leishmaniasis in Sao Paulo State, Brazil

AbstractWhen it comes to visceral leishmaniasis (VL) in Brazil, one of the main targets of public health policies of surveillance is the control of domestic canine reservoirs ofLeishmania infantum. This paper aims to evaluate the effect of the household environment risk in the maintenance of natural foci and in the transmission to human and animal hosts in an endemic city for VL, Bauru, in Brazil. We collected 6,578 blood samples of dogs living in 3,916 households from Nov.2019 to Mar.2020 and applied geospatial models to predict the disease risk based on the canine population. We used Kernel density estimation, cluster analysis, geostatistics and Generalized Additive Models (GAM). To validate our models, we used cross-validation and created a ROC graph. We found an overall canine VL (CVL) prevalence of 5.6%. Odds ratios (OR) for CVL increased progressively according to the number of canines for >2 dogs (OR 2.70); households that already had CVL in the past increased the chances for CVL currently (OR 2.73); and the cases of CVL increase the chances for human VL cases (OR 1.16). Our models were statistically significant and demonstrated an association between the canine and human disease, mainly in VL foci that remain endemic. Although the Kernel ratio map had the best performance (AUC=82), all the models showed high risk in the city’s northwest area. Canine population dynamics must be considered in public policies and geospatial methods may help target priority areas and planning VL surveillance in low and middle-income countries.HighlightsTwo or more dogs in a household increase the chances for canine visceral leishmaniasis.Canine visceral leishmaniasis or households with positive dogs increase the chances for human visceral leishmaniasis.Households that already had an infected dog increase the chances for canine visceral leishmaniasis, and it can work as silent endemic areas.More than 40 dogs in an area of influence of household (100m buffer) increase the chances for canine and human visceral leishmaniasis.Canine population dynamics must be considered in public policies regarding visceral leishmaniasis control in low and middle-income countries.Spatial analysis tools can bring new insights into decision-making and public policies regarding visceral leishmaniasis.