Intensified surveillance and insecticide-based control of the Chagas disease vector Triatoma infestans in the Argentinean Chaco.

GUREVITZ JM,; GASPE MS; ENRIQUE GF; PROVECHO YM.; KITRON U; GURTLER RE,

PLOS NEGLECTED TROPICAL DISEASES

PUBLIC LIBRARY SCIENCE

Lugar: San Francisco; Año: 2013 vol. 7 p. 2158 - 2158

1935-2735

Background: The elimination of Triatoma infestans, the main Chagas disease vector in the Gran Chaco region, remainselusive. We implemented an intensified control strategy based on full-coverage pyrethroid spraying, followed by frequentvector surveillance and immediate selective insecticide treatment of detected foci in a well-defined rural area innortheastern Argentina with moderate pyrethroid resistance. We assessed long-term impacts, and identified factors andprocedures affecting spray effectiveness.Methods and Findings: After initial control interventions, timed-manual searches were performed by skilled personnel in4,053 sites of 353–411 houses inspected every 4–7 months over a 35-month period. Residual insecticide spraying was lesseffective than expected throughout the three-year period, mainly because of the occurrence of moderate pyrethroidresistance and the limited effectiveness of selective treatment of infested sites only. After initial interventions, peridomesticinfestation prevalence always exceeded domestic infestation, and timed-manual searches consistently outperformedhouseholders’ bug detection, except in domiciles. Most of the infestations occurred in houses infested at baseline, and wererestricted to four main ecotopes. Houses with an early persistent infestation were spatially aggregated up to a distance of2.5 km. An Akaike-based multi-model inference approach showed that new site-level infestations increased substantiallywith the local availability of appropriate refugia for triatomine bugs, and with proximity to the nearest site found infested atone or two preceding surveys.Conclusions and Significance: Current vector control procedures have limited effectiveness in the Gran Chaco. Selectiveinsecticide sprays must include all sites within the infested house compound. The suppression of T. infestans in rural areaswith moderate pyrethroid resistance requires increased efforts and appropriate management actions. In addition to careful,systematic insecticide applications, housing improvement and development policies that improve material conditions ofrural villagers and reduce habitat suitability for bugs will contribute substantially to sustainable vector and disease control inthe Gran Chaco.