“Evaluation of current and potential Triatoma infestans vector control practices the Bolivian Chaco”

Introduction: This study aims to evaluate the current vector control against Triatoma infestans in a hyperendemic community in the Gran Chaco, and to pilot experiments towards its improvement. Methods: Four studies were conducted: (i) Assessment of Indoor Residual Spraying (IRS); evaluating householder compliance to empty their houses, the IRS application routine, and insecticide delivered dose; (ii) Mark-released recapture (MRR) to investigate the accuracy of methods to estimate infestation density, conducted in experimental huts; (iii) Evaluation of an educational intervention to improve Chagas disease Knowledge, Attitudes and Practices (KAP); (iv) Pilot study to test efficacy of housing improvement as a complement to vector control, comparing vector infestation and density in 3 treatment groups: House improvement + IRS (HI), Assisted IRS (AS), and Routine IRS (RS). Results: (i) Only 26% (15/58) of notified householders prepared their house to receive IRS; 19% (11/57) of houses presented median insecticide concentration at target dose; median insecticide concentrations were positively related to time spent spraying the house. (ii) Use of flushing-agent did not improve triatomine capture in artificial huts; increasing effort to 1 person/hour improved estimates of infestation in adobe huts; (iii) Baseline knowledge was considered deficient in disease transmission and moderate in vector ecology and biology. The educational intervention resulted in a moderated improvement of questionnaire scores for transmission and disease (d=0.63) and vector biology and ecology (d=0.70). However, the overall impact in scores improvement was considered large (Cohen d=0.88); (iv) In longitudinal analysis, all treatments presented reduction in triatomine density from baseline to a mean of 10 months post-treatment (GLM neg binomial: b=-0.006; z=-4.36; p