Key Source Habitats and Potential Dispersal of Triatoma infestans Populations in Northwestern Argentina: Implications for Vector Control

Abstract

Background Triatoma infestans —the principal vector of the infection that causes Chagas disease— defies elimination efforts in the Gran Chaco region. This study identifies the types of human-made or -used structures that are key sources of these bugs in the initial stages of house reinfestation after an insecticide spraying campaign.Methodology and Principal FindingsWe measured demographic and blood-feeding parameters at two geographic scales in 11 rural communities in Figueroa, northwest Argentina. Of 1,297 sites searched in spring, 279 (21.5%) were infested. Bug abundance per site and female fecundity differed significantly among habitat types (ecotopes) and were highly aggregated. Domiciles (human sleeping quarters) had maximum infestation prevalence (38.7%), human-feeding bugs and total egg production, with submaximal values for other demographic and blood-feeding attributes. Taken collectively peridomestic sites were three times more often infested than domiciles. Chicken coops had greater bug abundance, blood-feeding rates, engorgement status, and female fecundity than pig and goat corrals. The host-feeding patterns were spatially structured yet there was strong evidence of active dispersal of late-stage bugs between ecotopes. Two flight indices predicted that female fliers were more likely to originate from kitchens and domiciles, rejecting our initial hypothesis that goat and pig corrals would dominate.Conclusions and SignificanceChicken coops and domiciles were key source habitats fueling rapid house reinfestation. Focusing control efforts on ecotopes with human-fed bugs (domiciles, storerooms, goat corrals) would neither eliminate the substantial contributions to bug population growth from kitchens, chicken coops, and pig corrals nor stop dispersal of adult female bugs from kitchens. Rather, comprehensive control of the linked network of ecotopes is required to prevent feeding on humans, bug population growth, and bug dispersal simultaneously. Our study illustrates a demographic approach that may be applied to other regions and triatomine species for the design of innovative, improved vector control strategies.

Reservoir host competence and the role of domestic and commensal hosts in the transmission of Trypanosoma cruzi

“…The latter has rarely been investigated in the field (reviewed in Gürtler et al, 2014a) and is a key parameter of transmission models. Measuring the temperature-adjusted occurrence of transparent (clear) urine shortly after bug capture provides a widely applicable method for estimating daily feeding rates (Catalá, 1991).…”

“…Triatomine bugs make opportunistic feeding choices and therefore their host-feeding patterns tend to reflect the relative abundance and proximity of local hosts combined with host attractiveness and defensive behavior (Gürtler et al, 2014a(Gürtler et al, , 2009a. Seasonal variations in the host-feeding patterns of domestic T. infestans were related to changing host resting habits and exposure across seasons (Gürtler et al, 1997).…”

Evidence of selection on phenotypic plasticity and cost of plasticity in response to host-feeding sources in the major Chagas disease vector Triatoma infestans

“…infestans bugs from habitats with chickens associated (where bugs mostly or only fed on chickens) had greater blood-feeding rates and engorgement levels than bugs from pig corrals and goat corrals in the dry Argentine Chaco (Gürtler et al, 2014). Similarly, T. infestans males and females collected from chicken coops had significantly larger wing CS than those collected from pig or goat corrals and wood piles in a different study area (Schachter-Broide et al, 2004).…”

“…For example, head capsule is related directly to the substantial differences involved in bloodfeeding on mammalian and avian hosts or to their blood characteristics, whereas wings and the probability of flight initiation are related to other variables such as temperature, density, weight-length ratio and sex. The probability of flight initiation of T. infestans males exceeded that of females in the field (Gürtler et al, 2014;Vázquez-Prokopec et al, 2006) but not in 6 experimental settings (Gurevitz et al, 2006 and references therein). The relation between wing morphology and host-feeding source is plausible in view of the reported differences in wing size and shape and flight initiation probabilities across habitats and sexes (Gürtler et al, 2014;Schachter-Broide et al, 2004).…”

“…The probability of flight initiation of T. infestans males exceeded that of females in the field (Gürtler et al, 2014;Vázquez-Prokopec et al, 2006) but not in 6 experimental settings (Gurevitz et al, 2006 and references therein). The relation between wing morphology and host-feeding source is plausible in view of the reported differences in wing size and shape and flight initiation probabilities across habitats and sexes (Gürtler et al, 2014;Schachter-Broide et al, 2004).…”