Beating the odds: Sustained Chagas disease vector control in remote indigenous communities of the Argentine Chaco over a seven-year period

Abstract

BackgroundRapid reinfestation of insecticide-treated dwellings hamper the sustained elimination of Triatoma infestans, the main vector of Chagas disease in the Gran Chaco region. We conducted a seven-year longitudinal study including community-wide spraying with pyrethroid insecticides combined with periodic vector surveillance to investigate the house reinfestation process in connection with baseline pyrethroid resistance, housing quality and household mobility in a rural section of Pampa del Indio mainly inhabited by deprived indigenous people (Qom).Methodology/Principal findingsDespite evidence of moderate pyrethroid resistance in local T. infestans populations, house infestation dropped from 31.9% at baseline to 0.7% at 10 months post-spraying (MPS), with no triatomine found at 59 and 78 MPS. Household-based surveillance corroborated the rare occurrence of T. infestans and the house invasion of other four triatomine species. The annual rates of loss of initially occupied houses and of household mobility were high (4.6–8.0%). Housing improvements did not translate into a significant reduction of mud-walled houses and refuges for triatomines because most households kept the former dwelling or built new ones with mud walls.Conclusions/SignificanceOur results refute the assumption that vector control actions performed in marginalized communities of the Gran Chaco are doomed to fail. The larger-than-expected impacts of the intervention program were likely associated with the combined effects of high-coverage, professional insecticide spraying followed by systematic vector surveillance-and-response, broad geographic coverage creating a buffer zone, frequent housing replacement and residential mobility. The dynamical interactions among housing quality, mobility and insecticide-based control largely affect the chances of vector elimination.

Improved detection of house infestations with triatomines using sticky traps: a paired-comparison trial in the Argentine Chaco

“…Most of these devices offer a dry refuge for triatomines; some are resistant to outdoor conditions [24], and may include attractants or chemical baits and serve as traps [25,26]. Community-based vector surveillance conducted by householders, either in the form of bug notifications (HN) or bug collections (supplemented or not with a passive device), frequently performed similar to or better than TMC in domestic habitats [21,[27][28][29][30][31]. The validity of householder-based triatomine surveillance is affected by the vagaries of voluntary participation and shifting motivations, the skill of local residents, triatomine density, and whether householders provide proof of house infestation by returning triatomines to the designated receptors or not [18,27,30].…”

“…Community-based vector surveillance conducted by householders, either in the form of bug notifications (HN) or bug collections (supplemented or not with a passive device), frequently performed similar to or better than TMC in domestic habitats [21,[27][28][29][30][31]. The validity of householder-based triatomine surveillance is affected by the vagaries of voluntary participation and shifting motivations, the skill of local residents, triatomine density, and whether householders provide proof of house infestation by returning triatomines to the designated receptors or not [18,27,30]. Double-sided sticky tape (sticky traps, ST) adhered to specific substrates or habitats used by the target organisms has been used for arthropod detection in agricultural pest management programmes [32], and for monitoring of mosquito-borne human disease [33,34].…”

Impact Involving the Community in Entomological Surveillance of the Triatoma Infestans Vectorial Control

“…Despite methodological differences, there are many works showing a cost decrease when community collaborates in surveillance phase [8,10,11,19,20,22]. In this work, we recommended that community intervention is only in surveillance phase to guarantee an early triatomines detection but the spraying function is always responsibility of personnel speci cally trained for this task.…”

In search of Pan-American indigenous health and harmony

“…In example, within the Argentine region of the Gran Chaco ecoregion, which also includes sections of Bolivia and Paraguay, early household notification surveillance and community widespread spraying treatment led to a major decrease in triatomine, the major vector for Chagas disease. This research could be expanded to the Bolivia and Paraguay territories as well as expand in human screening and treatment of Chagas to correlate to triatomine elimination [24]. Studies such as these provide foundations for continual data analytics.…”

“…Environmental concerns threaten infectious disease increases, reproductive health, food sources and reduction in traditional plant medicine [19,20,26,57]. Socioeconomic disparities threaten poor health outcomes associated to poverty, and prejudice against indigenous has affected access to services [10,24]. The health of the indigenous continues to be of concern worldwide.…”