Limitations of selective deltamethrin application for triatomine control in central coastal Ecuador

Abstract

BackgroundThis 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.ResultsSurveys 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.ConclusionNew vector control strategies need to be devised and evaluated for reduction of T. cruzi transmission in this region.

Abundance, Natural Infection with Trypanosomes, and Food Source of an Endemic Species of Triatomine, Panstrongylus howardi (Neiva 1911), on the Ecuadorian Central Coast

“…Moreover, it is important to consider that an increased risk of invasion from the peridomicile to the domicile has been pointed out in previous reports of the presence of adults and nymphs of P. howardi in the peridomestic habitats of the houses nearby sylvatic environment 13 and the stable presence of peridomestic populations, despite periodic insecticide-based control. 16 However, to date, only one individual of this endemic species has been found in a sylvatic habitat associated with mouse nests in a palm of Aiphanes eggersi. 13 An important aspect to discuss is the overlapping distribution of P. howardi and T. dimidiata.…”

“…15 Previous studies have suggested that, although permeable to bugs, guadua cane walls do not offer good triatomine hiding places, possibly preventing colonization. 16 However, the environmental heterogeneity of the peridomestic habitat increases the probability of the presence of different species of triatomines. 17,18 The presence of sylvatic triatomines in this region 13 that can readily invade treated houses when residual effect of the insecticide declines constitutes a major obstacle for long-term control of Chagas disease.…”

“…17,18 The presence of sylvatic triatomines in this region 13 that can readily invade treated houses when residual effect of the insecticide declines constitutes a major obstacle for long-term control of Chagas disease. 16 Although little is known about its ecology and habitats, P. howardi has been shown to have strong synanthropic tendencies and should be considered as an important secondary vector of T. cruzi, especially in areas where the populations of primary vectors (e.g., T. dimidiata) are being eliminated from domestic and peridomestic environments.…”

Prevalence, Genetic Characterization, and 18S Small Subunit Ribosomal RNA Diversity of Trypanosoma rangeliin Triatomine and Mammal Hosts in Endemic Areas for Chagas Disease in Ecuador

“…However, none of those have included samples from Ecuador. Even though the presence of T. rangeli has been reported previously in triatomines and mammals from central coastal and southern Ecuador (Pinto et al 2006, Grijalva et al 2011 et al 2015), a detailed picture of its distribution and prevalence in these areas has not been assessed. The aim of this study was to contribute information about the diversity of the T. rangeli populations that are circulating in mammals and triatomines in the southern province of Loja and the central coastal province of Manabí, both considered as endemic areas for Chagas disease (Black et al 2007(Black et al , 2009).…”

“…Moreover, both T. cruzi and T. rangeli overlap their geographic distribution and share the same invertebrate (triatomines) and vertebrate (mammals) hosts. Mixed infection with both parasites has been reported (Vallejo et al 1988, Pinto et al 2006, Grijalva et al 2011, Villacis et al 2015. Chagas disease is listed by the World Health Organization (WHO) as one of the Neglected Topical Diseases that requires intensified research for integrated measures to improve health and social well-being of the affected populations (World Health Organization 2010).…”