Search

Abstract Background This year-long study evaluated the effectiveness of a strategy involving selective deltamethrin spraying and community education for control of Chagas disease vectors in domestic units located in rural communities of coastal Ecuador. Results Surveys for triatomines revealed peridomestic infestation with Rhodnius ecuadoriensis and Panstrongylus howardi, with infestation indices remaining high during the study (13%, 17%, and 10%, at initial, 6-month, and 12-month visits, respectively), which indicates a limitation of this strategy for triatomine population control. Infestation was found 6 and 12 months after spraying with deltamethrin. In addition, a large number of previously vector-free domestic units also were found infested at the 6- and 12-month surveys, which indicates new infestations by sylvatic triatomines. The predominance of young nymphs and adults suggests new infestation events, likely from sylvatic foci. In addition, infection with Trypanosoma cruzi was found in 65%, 21% and 29% at initial, 6-month and 12-month visits, respectively. All parasites isolated (n = 20) were identified as TcI. Conclusion New vector control strategies need to be devised and evaluated for reduction of T. cruzi transmission in this region.

The objective of this study was to evaluate the effectiveness of selective and community-wide house insecticide spraying in controlling triatomines in the subtropical areas of Loja Province, Ecuador. We designed a quasi-experimental pre-post-test without a control group to compare entomological levels before and after spraying. The baseline study was conducted in 2008. Second, third, and fourth visits were conducted in 2010, 2011, and 2012 in three rural communities. Out of the 130 domestic units (DU) visited, 41 domestic units were examined in each of the four visits. Selective and community-wide insecticide interventions included spraying with 5% deltamethrin at 25 mg/m 2 active ingredient. At each visit, a questionnaire was administered to identify the characteristics of households, and DUs were searched for triatomine bugs. In addition, parasitological analysis was carried out in life triatomines. One and two rounds of selective insecticide spraying decreased the probability of infestation by 62% (pairwise odds ratios [POR] 0.38, 95% confidence interval [CI] 0.17-0.89, p  = 0.024) and 51% (POR 0.49, 95% CI 0.23-1.01, p  = 0.054), respectively. A similar effect was observed after one round of community-wide insecticide application in Chaquizhca and Guara (POR 0.55, CI 0.24-1.25, p  = 0.155) and Bellamaria (POR 0.62, CI 0.22-1.79, p  = 0.379); however, it was not statistically significant. Trypanosoma cruzi infection in triatomines ( n  = 483) increased overtime, from 2008 (42.9% and 8.5% for Rhodnius ecuadoriensis and Panstrongylus chinai , respectively) to 2012 (79.5% and 100%). Neither of the two spraying methodologies was effective for triatomine control in this area and our results point to a high likelihood of reinfestation after insecticide application. This underscores the importance of the implementation of physical barriers that prevent invasion and colonization of triatomines in households, such as home improvement initiatives, accompanied by a concerted effort to address the underlying socioeconomic issues that keep this population at risk of developing Chagas disease.