Environmental influence on <em>Triatoma vitticeps</em> occurrence and <em>Trypanosoma cruzi</em> infection in the Atlantic Forest of south-eastern Brazil

Abstract

Trypanosoma cruzi requires a triatomine insect vector for its life cycle, which can be complex in different enzootic scenarios, one of which is the unique transmission network in the Atlantic Forest of south-eastern Brazil. In Espírito Santo (ES) State, highly infected Triatoma vitticeps are frequently reported invading domiciles. However, triatomines were not found colonizing residences and mammals in the surrounding areas did not present T. cruzi infection. To date, the biotic and abiotic variables that modulate T. vitticeps occurrence and T. cruzi infection in ES State are still unknown. The aim of this study was to identify the environmental variables that modulate their occurrence. Local thematic maps were generated for two response variables: T. vitticeps occurrence and T. cruzi infection. The following explanatory variables were tested: climate (temperature, relative air humidity and rainfall), altitude elevation, mammalian species richness as well as soil and vegetation types. Spatiotemporal distribution patterns and correlation levels between response and explanatory variables were assessed through spatial statistics and map algebra modelling. The central and southern mesoregions presented higher T. vitticeps and T. cruzi distributions and can be considered transmission hotspots. The explanatory variables that can explain these phenomena were relative air humidity, average temperature, soil type, altitude elevation and mammalian species richness. Algebra map modelling demonstrated that central and southern mesoregions presented the environmental conditions needed for T. vitticeps occurrence and T. cruzi infection. The consideration of environmental variables is essential for understanding the T. cruzi transmission cycle. Cartographic and statistical methodologies used in parasitology have been demonstrated to be reliable and enlightening tools that should be incorporated routinely to expand the understanding of vector-borne parasite transmission.

Profile of natural Trypanosoma cruzi infection among dogs from rural areas of southern Espírito Santo, Brazil

“…Other studies have shown the presence of the triatomine species T. vitticeps in 27 municipalities of Espírito Santo, including localities neighboring Alegre and Iconha. More than 85% of the triatomines captured were infected with flagellates morphologically similar to T. cruzi 8 , 9 . Recently, molecular approaches confirmed the presence of the flagellate species T. cruzi infecting T. vitticeps and P. geniculatus from the Atlantic Forest in southeastern Espírito Santo, in regions such as Caparaó and Litoral Sul, which geographically encompass the municipalities of Alegre and Iconha 27 .…”

“…The state of Espírito Santo, Brazil, has a low incidence of autochthonous human cases originating from infected sylvatic triatomine bugs in an epidemiological scenario wherein Triatoma vitticeps exhibits highest rate of natural infection, mainly attributed to its close relationship with wild mammals not refractory to T. cruzi 8 , 9 . In 2012, a fatal acute case of 2-year-old was reported after accidental oral ingestion of one T. cruzi -infected triatomine in Rio da Prata, a rural area of Guarapari 6 .…”

Space-environment relationship in the identification of potential areas of expansion of Trypanosoma cruzi infection in Didelphis aurita in the Atlantic Rainforest

“…The application of this geographic filter to generate the pseudo-absence points in this area C -O around each occurrence allows a significant improvement in the results [33]. The T. vitticeps exclusion buffer radius was 10 km [34], while its inclusion buffer was 60 km, approximately 90% of the median of the matrix of distances between occurrences. The exclusion buffer for P. megistus was the same as for T. vitticeps, while the inclusion buffer, due to its greater environmental diversity because of its greater spatial distribution along the Atlantic Forest, was defined as being 40% more than median of the matrix of distances between occurrences of T. vitticeps.…”