Effect of environmental variables on the incidence of Visceral Leishmaniasis in Brazil and Colombia

Visceral Leishmaniasis (VL) is the most severe of the three forms of Leishmaniasis. In the Americas, Brazil and Colombia present more than 90 % of the cases in the region. Our aim in this research was to estimate the association of the incidence rate of Visceral Leishmaniasis with the following environmental variables: the percentage of area suitable for the vector Lutzomyia longipalpis, the episodes of La Niña and El Niño, the Brazilian and Colombian biomes. Epidemiological data were obtained from the Brazilian Notifiable Diseases Information System and the Colombian National Public Health Surveillance System. Environmental data were downloaded from the NASA Giovanni web app, the Modis Sensor database, and the meteorological agencies of Australia, Japan, and the United States of America. Records of the presence of Lu. longipalpis were obtained from public databases and previous studies. As a result, the incidence per 10,000 inhabitants with LEBS for each El Niño-Southern Oscillation (ENSO) episode showed the largest values during El Niño 2015–2016, mainly in Brazil's Northeast and Central regions and the Northeast region of Colombia. Compared with the Neutral 2012–2014 episode, the episodes of El Niño 2015–2016 and La Niña 2010–2011 showed an average increase in the monthly incidence rate of VL, and the average increase was higher during El Niño 2015–2016 (aIRR = 2.304 vs.1.453) We found a positive association between the incidence rate of VL and the El Niño 2015–2016 episode and an impressive% of area suitable for the vector Lu. longipalpis in the Amazon region.An increase of 1 % in the area suitable for the vector Lu. longipalpis leads to an average rise of 0.8 % in the monthly incidence rate of VL. Our study shows a possible association between VL incidence and ENSO, with the most considerable incidence rates observed during El Niño 2015–2016 in Brazil's Northeast and Central regions and the Northeast region of Colombia. The present study is very important to better understand the Visceral Leishmaniasis transmission dynamics.