Abstract
When 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 of Leishmania infantum. This paper aims to evaluate the effect of the dog population and household environment for the maintenance of natural foci 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 receiver operating characteristic (ROC) curve. We found an overall canine VL (CVL) seroprevalence of 5.6% for the sampled dogs, while for the households, the positivity rate was 8.7%. 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 a spatial association between canine and human disease cases, mainly in VL foci that remain endemic. Although the Kernel density 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.
Highlights
Leishmaniasis is a group of infectious diseases caused by a protozoan of the Leishmania genus that affects humans and animals
Impact of the dog population and household environment for visceral leishmaniasis According to the Koppen-Geiger climate classification updated system [16, 17], Bauru climate is classified as Cfa, which means temperate, without dry season, and with hot Summer
Impact of the dog population and household environment for visceral leishmaniasis We found spatial clusters of high values in the west, north, east, south, northeast, southwest, southeast, and in Tibirica, a municipality district (Fig 4)
Summary
Leishmaniasis is a group of infectious diseases caused by a protozoan of the Leishmania genus that affects humans and animals. The transmission occurs by the bite of the dipterous of the subfamily Phlebotominae, the sand flies. It is considered one of the most widely distributed neglected diseases worldwide [1], being a health problem in North and East Africa, West and East Asia, and the Americas [2]. Visceral leishmaniasis (VL), for instance, is one of the most severe leishmaniasis. It threatens more than one billion and a half persons living in at-risk areas around the world. In the last update in 2021, Brazil notified 51,931 cases from 2005 to 2019, a mean of 3,462 per year [2]
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