Ecologia populacional de Triatoma maculata (Erichson, 1848) em três áreas rurais de Roraima, Brasil

Abstract

Triatoma maculata is a triatomine species adapted to human environments in northern Amazonia (state of Roraima, Brazil) and in parts of Venezuela and Colombia. It acts as an important vector of Chagas disease in Venezuela. In Roraima, populations of this species occur in wild, peridomestic and domestic (rural and urban) ecotopes, and have bionomic traits typical of a competent vector species. However, the ecology and epidemiological significance of these populations remain poorly understood. This project aimed at identifying and describing the features (structural and biotic) of artificial environments (houses and peridomestic areas) that may modulate the likelihood of infestation and colonization of those environments by T. maculata in rural Roraima; we also incorporated information on the way local residents relate to these synanthropic bugs and on their views of the associated health risks. Entomological surveys were carried out in 159 domiciliary units (DUs) of three rural areas (Uiramutã, Serra da Moça and Serra Tepequém). A KAP (knowledge, attitudes and practices) survey on Chagas disease and its vectors was conducted concomitantly. After the initial, exploratory analyses, inferential multivariate analyses were applied to the data. We built multivariate logistic regression models (and sets of models) and assessed their relative performance in a comparative framework using the Akaike Information Criterion with a correction for sample size (AICc). Covariates used to define the models described DU structural features (building materials, outbuildings etc.), the availability of food resources (domestic and opportunistic animals, humans), and control activities (insecticide spraying and/or others). The logit form of the best models (with lower AICc values) was used to assess the likely effects of different control interventions on the probabilities of infestation and colonization of the DUs by T. maculata. The standard entomological indices (over the three communities) were: overall infestation rate, 27,7%; colonization, 93,2%; density, ~12 specimens/DU; and crowding, ~47 specimens/infested DU. We collected 1,941 triatomines; colonies with >150 individuals were detected in five DUs. Vector presence was significantly less frequent in DUs of Serra Tepequém (6%) than in either Uiramutã (35%) or Serra da Moça (32%). Less than half of the residents knew Chagas disease, and only 32% of them mentioned triatomines as the transmission mechanism. The results of our modeling efforts suggested a key role for the combination of structural traits and food resource availability on the probability that a given DU was infested or colonized by T. maculata; models assessing structure and resources separately performed much worse. Mud walls without complete plastering and the number of chicken kept at the DU appeared as the main risk factors; however, the data suggest that these vector populations exploit alternative food resources, particularly rodents and humans. Trypanosoma cruzi transmission cycles are therefore more likely to emerge in DUs where abundant resources are available in the context of a suitable physical structure; the application of insecticides had no apparent effect. Control strategies should combine plastering walls (with locally available materials and technology), rodent population control, and a better management of poultry; traditional thatched roofs did not increase infestation probabilities. Malaria control strategies should be adapted (product formulation, application techniques etc.) so that their effects on synanthropic triatomine populations are optimized.