Abstract
BackgroundFor Chagas disease, the most serious infectious disease in the Americas, effective disease control depends on elimination of vectors through spraying with insecticides. Molecular genetic research can help vector control programs by identifying and characterizing vector populations and then developing effective intervention strategies.Methods and FindingsThe population genetic structure of Triatoma infestans (Hemiptera: Reduviidae), the main vector of Chagas disease in Bolivia, was investigated using a hierarchical sampling strategy. A total of 230 adults and nymphs from 23 localities throughout the department of Chuquisaca in Southern Bolivia were analyzed at ten microsatellite loci. Population structure, estimated using analysis of molecular variance (AMOVA) to estimate FST (infinite alleles model) and RST (stepwise mutation model), was significant between western and eastern regions within Chuquisaca and between insects collected in domestic and peri-domestic habitats. Genetic differentiation at three different hierarchical geographic levels was significant, even in the case of adjacent households within a single locality (R ST = 0.14, F ST = 0.07). On the largest geographic scale, among five communities up to 100 km apart, R ST = 0.12 and F ST = 0.06. Cluster analysis combined with assignment tests identified five clusters within the five communities.ConclusionsSome houses are colonized by insects from several genetic clusters after spraying, whereas other households are colonized predominately by insects from a single cluster. Significant population structure, measured by both R ST and F ST, supports the hypothesis of poor dispersal ability and/or reduced migration of T. infestans. The high degree of genetic structure at small geographic scales, inferences from cluster analysis and assignment tests, and demographic data suggest reinfesting vectors are coming from nearby and from recrudescence (hatching of eggs that were laid before insecticide spraying). Suggestions for using these results in vector control strategies are made.
Highlights
Some houses are colonized by insects from several genetic clusters after spraying, whereas other households are colonized predominately by insects from a single cluster
Chagas disease is a parasitic disease in which the pathogenic agent, Trypanosoma cruzi is transmitted by hematophagous insects of the sub-family Triatominae
This study focuses on T. infestans in the Department of Chuquisaca, Bolivia
Summary
Chagas disease is a parasitic disease in which the pathogenic agent, Trypanosoma cruzi is transmitted by hematophagous insects of the sub-family Triatominae. In 1991 a public health program, the Southern Cone Initiative was launched by the World Health Organization to eliminate vector populations [4], through spraying of houses and surrounding areas with pyrethroid insecticides [5]. In Argentina, Brazil, Chile, and Uruguay, T. infestans is exclusively domestic or peri-domestic, eradication of the vector in these regions, followed by vigilance against reinfestation, has proven largely successful in reducing transmission of T. cruzi and the prevalence of Chagas disease [6]. In Bolivia the vectors occur in domestic, peri-domestic, and sylvatic environments [7]; control of T. infestans in towns and homesteads is confounded by the possible re-infestation from surrounding sylvatic areas. For Chagas disease, the most serious infectious disease in the Americas, effective disease control depends on elimination of vectors through spraying with insecticides. Molecular genetic research can help vector control programs by identifying and characterizing vector populations and developing effective intervention strategies
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