Abstract

House re-invasion by native triatomines after insecticide-based control campaigns represents a major threat for Chagas disease vector control. We conducted a longitudinal intervention study in a rural section (Area III, 407 houses) of Pampa del Indio, northeastern Argentina, and used wing geometric morphometry to compare pre-spray and post-spray (re-infestant bugs) Triatoma infestans populations. The community-wide spraying with pyrethroids reduced the prevalence of house infestation by T. infestans from 31.9% to < 1% during a four-year follow-up, unlike our previous studies in the neighbouring Area I. Two groups of bug collection sites differing in wing shape variables before interventions (including 221 adults from 11 domiciles) were used as a reference for assigning 44 post-spray adults. Wing shape variables from post-spray, high-density bug colonies and pre-spray groups were significantly different, suggesting that re-infestant insects had an external origin. Insects from one house differed strongly in wing shape variables from all other specimens. A further comparison between insects from both areas supported the existence of independent re-infestation processes within the same district. These results point to local heterogeneities in house re-infestation dynamics and emphasise the need to expand the geographic coverage of vector surveillance and control operations to the affected region.

Highlights

  • House re-invasion by native triatomines after insecticide-based control campaigns represents a major threat for Chagas disease vector control

  • House re-infestation by T. infestans - Baseline house infestation by T. infestans (31.9%) dropped sharply and remained below 1% during the four-year follow-up after community-wide insecticide spraying of Area III, unlike in neighbouring after control interventions in a rural section (Area I) (Fig. 2)

  • This study does not support our a priori hypothesis that the detected re-infestations during the four-year follow-up of Area III were primarily due to residual foci that survived community-wide insecticide spraying, unlike in Area I

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Summary

Introduction

House re-invasion by native triatomines after insecticide-based control campaigns represents a major threat for Chagas disease vector control. We conducted a longitudinal intervention study in a rural section (Area III, 407 houses) of Pampa del Indio, northeastern Argentina, and used wing geometric morphometry to compare pre-spray and post-spray (re-infestant bugs) Triatoma infestans populations. A further comparison between insects from both areas supported the existence of independent re-infestation processes within the same district These results point to local heterogeneities in house re-infestation dynamics and emphasise the need to expand the geographic coverage of vector surveillance and control operations to the affected region. In the absence of an effective vaccine, the main strategy to reduce or interrupt vectorborne transmission of Trypanosoma cruzi is associated with the elimination or reduction of domestic triatomine populations, mainly through the application of insecticide These interventions suppressed Triatoma infestans, the main vector species in the Southern Cone countries, from a large area of its original geographic range (Schofield et al 2006). To further test the generality of these results, we expanded the scope and geographic scale of the research and control operations to a neighbouring rural section (Area III) of Pampa del Indio, which had high pre-intervention infestation, but contrasting environmental, socio-demographic and cultural characteristics (Gaspe et al 2015)

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