Abstract
BackgroundTriatoma infestans is the main vector of Trypanosoma cruzi in Bolivia. The species is present both in domestic and peridomestic structures of rural areas, and in wild ecotopes of the Andean valleys and the Great Chaco. The identification of areas persistently showing low and high house infestation by the vector is important for the management of vector control programs. This study aimed at analyzing the temporal and spatial distribution of house infestation by T. infestans in the Toro Toro municipality (Potosi, Bolivia) between 2009 and 2014, and its association with environmental variables.MethodsHouse infestation and T. infestans density were calculated from entomological surveys of houses in the study area, using a fixed-time effort sampling technique. The spatial heterogeneity of house infestation was evaluated using the SatScan statistic. Association between house infestation with Bioclim variables (Worldclim database) and altitude was analyzed using a generalized linear model (GLM) with a logit link. Model selection was based on the Akaike information criteria after eliminating collinearity between variables using the variable inflation factor. The final model was used to create a probability map of house infestation for the Toro Toro municipality.ResultsA total of 73 communities and 16,489 house evaluation events were analyzed. Presence of T. infestans was recorded on 480 house evaluation events, giving an overall annual infestation of 2.9% during the studied period (range 1.5–5.4% in 2009 and 2012). Vector density remained at about 1.25 insects/ house. Infestation was highly aggregated in five clusters, including 11 communities. Relative risk of infestation within these clusters was 1.7–3.9 times the value for the regional average. Four environmental variables were identified as good descriptors of house infestation, explaining 57% of house infestation variability. The model allowed the estimation of a house infestation surface for the Toro Toro municipality.ConclusionThis study shows that residual and persistent populations of T. infestans maintain low house infestation, representing a potential risk for the transmission of T. cruzi in these communities, and it is possible to stratify house infestation using EV, and produce a risk map to guide the activities of vector control interventions in the municipality of Toro Toro (Potosi, Bolivia).
Highlights
Triatoma infestans is the main vector of Trypanosoma cruzi in Bolivia
Higher density was observed during 2011 and 2012, vector density remained at about 1.25 insects per infested house
Only the Departments of La Paz and Potosi were certified free of vectorial transmission [1, 18], the species persists in reduced population remnants throughout these Departments
Summary
Triatoma infestans is the main vector of Trypanosoma cruzi in Bolivia. The species is present both in domestic and peridomestic structures of rural areas, and in wild ecotopes of the Andean valleys and the Great Chaco. In Latin America, the main vector is Triatoma infestans, a species widely distributed on the continent [4, 5], showing high vectorial capacity for the transmission of T. cruzi, because of its close association with man [6] and habitation of domestic and peridomestic structures [7]. The Potosi Department, in the south of Bolivia, is considered one of the poorest (86% poverty), and has precarious housings that favor the establishment and development of triatomines (a scenario generally described in highly endemic areas of Chagas disease) [14,15,16,17] These features are currently responsible for the persistence of T. infestans in 20 of the 40 provinces in the municipality of Toro Toro [18]
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