Visceral leishmaniasis and its relationship with climate and environmental factors in the State of Tocantins, Brazil, from 2007 to 2014

Abstract: Visceral leishmaniasis (VL) may be influenced by climate and environmental factors. Tocantins is the state with the highest incidence in Brazil, contributing to the increase in the number of cases in the North macro-region. This study seeks to identify the correlation between VL incidence rates and climate and environmental factors in the municipalities of the State of Tocantins between 2007 and 2014. Correlations between crude VL incidence rates and the variables elevation, precipitation, Enhanced Vegetation Index (EVI) and temperature were tested using the Global and Local Moran Indexes, while also identifying clusters of VL incidence. We tested a variance analysis for linear trend between variable means in each rate category. Results show an increase in incidence rates with an increase in values of annual precipitation, humidity, EVI and nighttime temperature; and an inverse relationship with elevation and daytime temperature. The clusters we identified show that climate and environmental variables are related to VL incidence. Other studies are needed that adjust for individual-related factors in order to gauge how much the environment, or human influence over it, impact the disease.