Geographic distribution of chagas disease vectors in Brazil based on ecological niche modeling

Abstract

Although Brazil was declared free from Chagas disease transmission by the domestic vector Triatoma infestans, human acute cases are still being registered based on transmission by native triatomine species. For a better understanding of transmission risk, the geographic distribution of Brazilian triatomines was analyzed. Sixteen out of 62 Brazilian species that both occur in >20 municipalities and present synanthropic tendencies were modeled based on their ecological niches. Panstrongylus geniculatus and P. megistus showed broad ecological ranges, but most of the species sort out by the biome in which they are distributed: Rhodnius pictipes and R. robustus in the Amazon; R. neglectus, Triatoma sordida, and T. costalimai in the Cerrado; R. nasutus, P. lutzi, T. brasiliensis, T. pseudomaculata, T. melanocephala, and T. petrocchiae in the Caatinga; T. rubrovaria in the southern pampas; T. tibiamaculata and T. vitticeps in the Atlantic Forest. Although most occurrences were recorded in open areas (Cerrado and Caatinga), our results show that all environmental conditions in the country are favorable to one or more of the species analyzed, such that almost nowhere is Chagas transmission risk negligible.

Figure 1

Relative occurrence of 16 species of triatomines across biomes, calculated based on proportions of known occurrences falling in each area.

Figure 2

Ecological niche models projected as potential distributions for triatomine species with widespread distribution in Brazil. (a) Panstrongylus geniculatus and (b) P. megistus. Known occurrences of the species are shown as yellow squares, and the final consensus prediction is shown as black shading. Areas identified as suitable based on climatic grounds only are shown in blue, whereas areas identified as suitable based on normalized difference vegetation index (NDVI) only are shown in green.

Figure 3

Ecological niche models projected as potential distributions for triatomine species in central Brazil. (a) R. neglectus, (b) T. costalimai, and (c) T. sordida.

Figure 4

Ecological niche models projected as potential distributions for triatomine species in northeastern Brazil. (a) R. nasutus, (b) P. lutzi, (c) T. brasiliensis, (d) T. pseudomaculata, (e) T. melanocephala, and (f) T. petrocchiae.

Figure 5

Ecological niche models projected as potential distributions for Amazonian triatomine species. (a) R. robustus, and (b) R. pictipes.

Figure 6

Ecological niche models projected as potential distribution for T. rubrovaria.

Figure 7

Ecological niche models projected as potential distributions for Atlantic Forest triatomine species. (a) T. tibiamaculata and (b) T. vitticeps.

Figure 8

Triatomine species diversity map of Brazil, based on ecological niche models for 16 species of triatomine bugs. White areas have no species predicted as occurring, out of the 16 included in this analysis, while the darkest red areas have 13 species predicting as cooccurring.

Figure 9

Distribution of 16 triatomine species in Brazil with respect to environmental variation summarized as the first two principal components summarizing variation in seven climatic dimensions. To provide a view of species' responses to environmental variation across Brazil, we plotted 1000 random points across the country, and assigned to each (1) the predicted presence or absence of each species and (2) the values of the first two principal components extracted from the bioclimatic data set.