Active dispersal by wild Triatoma infestans in the Bolivian Andes

Abstract

SummaryTriatoma infestans is the main vector of Chagas disease and target of control programmes in the Southern Cone countries. So far Bolivia is the only country where true T. infestans wild foci are documented. The dispersal ability for wild T. infestans was studied at microgeographical scale in Bolivian Andes, to assess the possibility for wild populations to actively recolonize insecticide-treated villages. Nine microsatellite loci were used to detect the extent of gene flow between neighbouring collecting sites. The detection of restricted gene flow between close but distinct sylvatic sites supports the hypothesis that wild T. infestans does not disperse by flying at high altitude (2 750 m asl). It gradually disperses over small distances by walking within a 'patch' of continuous land cover. The genetic differentiation detected between sylvatic and domestic populations suggests a limited short-term role of wild insects in the process of recolonization of insecticide-treated houses in the Andes.

Wild Triatoma infestans, a potential threat that needs to be monitored

“…Therefore, it is essential to assess the dispersal of wild T. infestans and the extent of gene flow between sylvatic and domestic populations. In a dispersal study performed in the Cochabamba valley at 2,700 m asl, the detection of restricted gene flow between close, but distinct, sylvatic sites (rocky outcrops) was consistent with the hypothesis that the vectors do not disperse by flying at high altitude (Richer et al 2007). Some studies on the ability of T. infestans to fly under more favourable conditions (in the lowlands of the Chaco) pointed out that this species showed flight potential on a village-wide scale and in sylvatic environments (Schofield et al 1992, Vazquez-Prokopec et al 2006.…”

“…Some studies on the ability of T. infestans to fly under more favourable conditions (in the lowlands of the Chaco) pointed out that this species showed flight potential on a village-wide scale and in sylvatic environments (Schofield et al 1992, Vazquez-Prokopec et al 2006. However, the results of Richer et al (2007) suggested that, at 2,700 m asl in the Andes, wild T. infestans gradually disperse over a small distance by walk-ing within a "patch", which might be characterised as a continuous land cover with all necessary resources for the persistence of triatomine populations (Gustafson & Gardner 1996). On the other hand, when the land cover is disrupted by human activities (e.g., building of dwellings and peridomestic structures, land or livestock farming), triatomine bugs encounter an unsuitable environment and cannot spread to separate patches by walking.…”

Ecological host fitting of Trypanosoma cruzi TcI in Bolivia: mosaic population structure, hybridization and a role for humans in Andean parasite dispersal

“…The lower genetic diversity observed among highlands strains may reflect more restricted feeding preferences and limited independent dispersal of their host vector species Triatoma infestans (<500 m) (Rabinovich & Himschoot 1990; Richer et al . 2007). As a more recent host of TcI, vector competency of sylvatic T. infestans may also vary, particularly in terms of bottlenecks during transmission, which can further reduce genetic diversity, as demonstrated in tsetse fly vectors of other digenetic trypanosome species (Ruepp et al .…”

“…Indeed, didelphid marsupials and Rhodnius vectors have a far greater capacity for auto‐dissemination than T. infestans and smaller rodents (Richer et al . 2007). Instead, parasite dispersal across the highlands may be recent and anthroponotic.…”

Genetics and evolution of triatomines: from phylogeny to vector control

“…infestans populations are generally highly structured as shown by allozyme analyses (Dujardin et al, 1987(Dujardin et al, , 1998aBrenière et al, 1998) and microsatellite markers (Table 2), as might be expected for a mostly domestic species. Interestingly, in areas where T. infestans has extensive sylvan populations, gene flow was also restricted among these sylvan populations and largely absent between the sylvan and domestic populations (Richer et al, 2007 and Table 2). Recent analysis of genomic (Perez de Rosas et al, 2011) and mtDNA (Torres-Perez et al, 2011) both support the hypothesis of two independent migration events of T. infestans in South America, and confirmed the existence of two distinct lineages.…”