Abstract
Triatoma infestans, the major vector of Chagas disease south of the Amazon in South America, has a large distribution of wild populations, contrary to what has previously been stated. These populations have been suspected of being the source of reinfestation of human habitats and could impede the full success of vector control campaigns. This study examined gene flow between intra-peridomestic populations and wild populations collected in the surround areas in three Andean localities in Bolivia. The populations were defined according to temporal, ecological, and spatial criteria. After DNA extraction from the legs of each insect, the samples were analyzed using seven microsatellite markers. First, the analysis of molecular variance (AMOVA) detected an absence of differentiation between wild and intra-peridomestic populations, although strong structuring was observed between the populations within each environment. Then for some populations, the Bayesian method of assignment to inferred populations showed very similar assignment patterns of the members of wild or intra-peridomestic populations in each locality. Finally, the detection of the first-generation migrants within the different populations provided evidence of insect displacement from the wild to the intra-peridomestic environment. This result indicates that, after control campaigns in the Andes, controlling this new paradigm of vector transmission risk stemming from the invasion of human habitats by wild populations of T. infestans requires long-term maintenance of public monitoring to keep the risk at a minimal level. Since wild populations of T. infestans have also been detected elsewhere in Argentina, Paraguay, and Chile, there is an urgent need to take these populations into account in future monitoring of Chagas disease transmission.
Highlights
IntroductionIn the Southern Cone countries of South America and in Bolivia, Triatoma infestans (Reduviidae, Triatominae) remains the main and most widespread vector of Trypanosoma cruzi, the causative agent of Chagas disease
In the Southern Cone countries of South America and in Bolivia, Triatoma infestans (Reduviidae, Triatominae) remains the main and most widespread vector of Trypanosoma cruzi, the causative agent of Chagas disease. This species has long been considered almost exclusively domestic, but the increase in wild population discoveries in the Andes, in the Gran Chaco lowland region, and in Chile shows that wild T. infestans populations are much more widespread than previously thought [1,2,3,4,5,6,7]; the potential map of the distribution of wild T. infestans, based on an earlier sample of Bolivian and Argentinean wild foci, supports a very wide distribution [8]
Data from seven previously described microsatellite loci were analyzed for a total of 277 T. infestans specimens collected in three localities in wild and domestic environments (Sapini, Quillacollo and Thago Thago)
Summary
In the Southern Cone countries of South America and in Bolivia, Triatoma infestans (Reduviidae, Triatominae) remains the main and most widespread vector of Trypanosoma cruzi, the causative agent of Chagas disease This species has long been considered almost exclusively domestic, but the increase in wild population discoveries in the Andes, in the Gran Chaco lowland region, and in Chile shows that wild T. infestans populations are much more widespread than previously thought [1,2,3,4,5,6,7]; the potential map of the distribution of wild T. infestans, based on an earlier sample of Bolivian and Argentinean wild foci, supports a very wide distribution [8]. Determining whether the success in eliminating vectors could be disrupted by repeated reinfestations of dwellings and peridomestic areas by the nearby wild populations remains an open question In this case, the current vigilance system, based on selective insecticide spraying of dwellings where vectors are resurgent, remains of limited efficacy and new control strategies must be developed [4,11,12,13]
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