Influence of the landscape on dispersal of sylvatic triatomines to anthropic habitats in the Atlantic Forest

Abstract

Aim The aim of this study was to test the hypothesis that the dispersal of sylvatic triatomines to anthropic habitats is stimulated by degradation of their natural habitat.Location State of Espírito Santo, south-eastern Brazil.Methods We georeferenced records of domiciliary captures of sylvatic triatomines (1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005) obtained from the database of the entomological surveillance programme of the Brazilian National Health Foundation. We partitioned the study area into 543 equal hexagons and attributed information on the presence/absence of triatomines and climatic, topographic and biological variables to each. Using generalized additive models (GAMs), we defined the determinant variables for triatomine presence/absence and demarcated the potential areas in which they might occur. We then subjected the hexagons with a high probability of triatomine presence to a second analysis, adding information on the number of domiciliary captures of triatomines and landscape indices that measured quantitative and spatial patterns of forest fragments. We used GAMs to determine the indices that influenced the number of domiciliary captures of triatomines. ResultsThe presence of triatomines was characterized by a strong positive correlation with variability of terrain slope. This variable was used to demarcate the areas where triatomines were likely to occur. Landscape indices associated with the number of domiciliary captures of triatomines were the number of patches, the fractal dimension index, the total core area and the clumpiness index. Main conclusionsOur results do not support the hypothesis that domiciliary invasion by sylvatic triatomines is stimulated by environmental degradation. Instead, the results suggest that less degraded areas maintain larger populations of triatomines and consequently present higher indices of dispersal and domiciliary invasion. Particular landscape patterns and dispositions of human dwellings, however, may enhance the probability of triatomines being attracted to the artificial light of dwellings. Initiation of flight and consequent dispersal is a naturally occurring process that allows triatomines to find and colonize areas that favour the survival of their offspring.

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

“…Areas with steep slopes have dimples, which allow a greater variability of water and organic matter accumulation, as well as a reduction in sunlight and wind exposure, thereby creating a greater diversity of habitats; this diversity in habitats contributes to the maintenance of food and shelter conditions for these insects [33]. …”

Climatic factors influencing triatomine occurrence in Central-West Brazil

“…Other studies have shown temperature to be an important determinant of the distribution of triatomines on a regional or continental scale (Gorla 2002, Rodriguero & Gorla 2004, Batista & Gurgel-Gonçalves 2009, Gurgel-Gonçalves & Silva 2009, Gurgel-Gonçalves et al 2011). However, other environmental variables, such as the slope of the terrain (Leite et al 2011) and humidity (Arboleda et al 2009), have also been identified as principal determinants of the occurrence of certain species.…”

Dynamics of Sylvatic Chagas Disease Vectors in Coastal Ecuador Is Driven by Changes in Land Cover

“…The vectors are blood-sucking reduviid bugs of the subfamily Triatominae, of which 70 of the over 140 Triatominae species described [3], [4] have been found to be naturally infected with T. cruzi [5]. Originally restricted to sylvatic habitats, Chagas disease began to present a risk to human health as its vectors acquired the ability to colonize and sustain populations in human dwellings, resulting in the domiciliary transmission of T. cruzi [6].…”