Environmental Niche Modelling of Phlebotomine Sand Flies and Cutaneous Leishmaniasis Identifies Lutzomyia intermedia as the Main Vector Species in Southeastern Brazil

Abstract

Cutaneous leishmaniasis (CL) is caused by a protozoan of the genus Leishmania and is transmitted by sand flies. The state of Espírito Santo (ES), an endemic area in southeast Brazil, has shown a considerably high prevalence in recent decades. Environmental niche modelling (ENM) is a useful tool for predicting potential disease risk. In this study, ENM was applied to sand fly species and CL cases in ES to identify the principal vector and risk areas of the disease. Sand flies were collected in 466 rural localities between 1997 and 2013 using active and passive capture. Insects were identified to the species level, and the localities were georeferenced. Twenty-one bioclimatic variables were selected from WorldClim. Maxent was used to construct models projecting the potential distribution for five Lutzomyia species and CL cases. ENMTools was used to overlap the species and the CL case models. The Kruskal–Wallis test was performed, adopting a 5% significance level. Approximately 250,000 specimens were captured, belonging to 43 species. The area under the curve (AUC) was considered acceptable for all models. The slope was considered relevant to the construction of the models for all the species identified. The overlay test identified Lutzomyia intermedia as the main vector of CL in southeast Brazil. ENM tools enable an analysis of the association among environmental variables, vector distributions and CL cases, which can be used to support epidemiologic and entomological vigilance actions to control the expansion of CL in vulnerable areas.

High-resolution habitat suitability model for Phlebotomus pedifer, the vector of cutaneous leishmaniasis in southwestern Ethiopia

“…6). The importance of the climate variables is consistent with other studies mapping the distribution of leishmaniasis and its vectors [17,64,[66][67][68].…”

“…The obvious 'belt' around the higher mountains indicates that the environment is unsuitable for the presence of the vector up to and as of a certain height. In many studies, elevation is included as a response variable in the model [17,20,[65][66][67]. However, this variable can have different environmental characteristics in different areas (depending on the slope, aspect, wind, etc.)…”

“…Other studies modeling the distribution of vectors commonly use a 1 km spatial resolution because climate layers are only available at this coarse resolution [66,67,[76][77][78]. Because climate variables are often the most important predictors for SDMs of disease vectors, these data should be very detailed [36,66,67,76]. Moreover, recently SDMs are being used for optimization of vector control, so it is bene cial for coordination of resource allocation for targeted control measures to have smaller grids indicating the suitable habitats of the vector [18].…”

Species-specific ecological niche modelling predicts different range contractions for Lutzomyia intermedia and a related vector of Leishmania braziliensis following climate change in South America

“…The shifting distributions of L. intermedia and L. neivai in response to climate change will affect regional investigations of transmission cycles, including those using overlaid ecological niche models of Leishmania and its vectors in south-east Brazil [21]. Because climate is a first order determinant of the spatial distribution of species [46, 70], predictive models at finer spatial scales are needed to guide more precise assessments of disease risk and surveillance.…”

Effects of habitat suitability for vectors, environmental factors and host characteristics on the spatial distribution of the diversity and prevalence of haemosporidians in waterbirds from three Brazilian wetlands

“…Several studies have focused on the detection of haemosporodians in birds and the spatial distribution of blood parasites, but ecological factors, such as vector abundance, has been insufficiently explored, despite being considered an important factor [ 73 ]. The present investigation contributes information on vector abundance using an indirect ecological niche modelling approach that has been useful to understanding the potential distribution of the vector species, such as in the case of the transmission of cutaneous leishmaniasis [ 74 ]. Behind this proposal is the assumption that more suitable niches imply a greater number of vectors, which would consequently result in a greater diversity and prevalence of haemosporidians.…”