Modeling the spatial distribution of Chagas disease vectors using environmental variables and people´s knowledge

Jaime Hernández,Antonella Bacigalupo,Ignacia Núñez,Pedro E Cattan

doi:10.1186/1476-072x-12-29

Jaime Hernández, Antonella Bacigalupo + Show 2 more

Open Access

https://doi.org/10.1186/1476-072x-12-29

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Abstract

BackgroundChagas disease is caused by the protozoan Trypanosoma cruzi, which is transmitted to mammal hosts by triatomine insect vectors. The goal of this study was to model the spatial distribution of triatomine species in an endemic area.MethodsVector’s locations were obtained with a rural householders’ survey. This information was combined with environmental data obtained from remote sensors, land use maps and topographic SRTM data, using the machine learning algorithm Random Forests to model species distribution. We analysed the combination of variables on three scales: 10 km, 5 km and 2.5 km cell size grids.ResultsThe best estimation, explaining 46.2% of the triatomines spatial distribution, was obtained for 5 km of spatial resolution. Presence probability distribution increases from central Chile towards the north, tending to cover the central-coastal region and avoiding areas of the Andes range.ConclusionsThe methodology presented here was useful to model the distribution of triatomines in an endemic area; it is best explained using 5 km of spatial resolution, and their presence increases in the northern part of the study area. This study’s methodology can be replicated in other countries with Chagas disease or other vectorial transmitted diseases, and be used to locate high risk areas and to optimize resource allocation, for prevention and control of vectorial diseases.

Highlights

Chagas disease is caused by the protozoan Trypanosoma cruzi, which is transmitted to mammal hosts by triatomine insect vectors
Distribution of positive cases The results indicated that 14.3% of the rural houses surveyed were positive cases
The habitat of M. spinolai and T. infestans maybe overlapping more than expected, a situation that reveals the advantage of studying both species together and not separately

Summary

Introduction

Chagas disease is caused by the protozoan Trypanosoma cruzi, which is transmitted to mammal hosts by triatomine insect vectors. The prevalence of M. spinolai, detected by molecular techniques, varies between 42.7% to 76.1% [6,11,12] in sylvatic foci; the few individuals of this species that were captured in dwellings and sent to the National Health Service presented 22.8% of infection in the study area [13]. Triatoma infestans was found recently in sylvatic environments, associated to endemic terrestrial bromeliads in the Metropolitana Region, with a prevalence of 40.9% [6], and rock piles in the Valparaíso Region, with 36.5% of infection [17], along with periodic findings inside human dwellings, which mainly correspond to winged adults; the infection in the study area was reported to be 48.4% [13]. Recent reports on human seroprevalence of T. cruzi infection in a national health survey indicated 1.8%, 0.9% and 0.7% in Coquimbo Region, Valparaíso Region and Metropolitana Region, respectively [19]

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