Variability of susceptibility to deltamethrin in peridomestic Triatoma sordida from Triângulo Mineiro, State of Minas Gerais, Brazil

Abstract

Introduction: Despite chemical and physical vector control strategies, persistent infestations of Triatoma sordida have been reported in a large part of Minas Gerais, Brazil, and the cause for this is little investigated. We aimed to characterize the deltamethrin toxicological profi le in peridomestic T. sordida populations from Triângulo Mineiro area of Minas Gerais. Methods: Susceptibility to deltamethrin was assessed in seventeen peridomestic T. sordida populations. Serial dilutions of deltamethrin in acetone (0.2µL) were topically applied on the fi rst instar nymphs (F1; fi ve days old; fasting weight, 1.2 ± 0.2mg). Dose response results were analyzed using Probit software, and the lethal doses, slope and resistance ratios were determined. Qualitative tests were also performed. Results: The deltamethrin susceptibility profi le of T. sordida populations revealed resistance ratios ranging from 0.84 to 2.8. The percentage mortality in response to a diagnostic dose was 100.0% in all populations. Conclusions: From our results, the lack of resistance to insecticides but persistent T. sordida infestations in the Triângulo Mineiro area may be because of: 1) environmental degradation facilitating dispersion of T. sordida, allowing colonization in artifi cial ecotopes; 2) operational failures; and 3) complexity of the peridomicile in the study area.These variables are being investigated.

Conhecimentos sobre os triatomíneos e a doença de Chagas em habitantes do município de Barra, Bahia

“…A alta densidade triatomínea do peridomicílio, exerce uma pressão para colonização no interior das residências. Além desse fator, o baixo teor residual de inseticidas no entorno das moradias favorece a ocorrência desses insetos neste ambiente, somados a precária limpeza e organização das instalações por parte dos moradores (Mendes et al, 2013;Pessoa et al, 2015).…”

“…Outro ponto que deve ser considerado é a atração dos triatomíneos por fontes luminosas externas, adentrando assim os domicílios. Isso proporciona a ocorrência desses insetos em locais como a varanda e áreas de serviço mencionado no nosso estudo, favorecendo a invasão noturna dos domicílios (Pessoa et al, 2015).…”

Resistance to deltamethrin by domestic and wild Triatoma infestans populations in the municipality of Toro Toro, Potosi, Bolivia

“…For each insecticide dose, three replicates were performed with 10 instar F1 generation nymphs (five days, fasting, weight of 1.2 ± 0.2 mg). The topical application was through 0.2 μl of insecticide dilution in the dorsal abdomen, according to the procedures of the World Health Organization [ 39 ] and Pessoa et al [ 40 ]. After treatment, mortality was assessed 72 h post-application and determined by the inability or lack of coordination of the nymphs to move from center to the edge of the filter paper (7 cm diameter).…”

Effect of salivary CYP4EM1 and CYP4EM2 gene silencing on the life span of Chagas disease vector Rhodnius prolixus (Hemiptera, Reduviidae) exposed to sublethal dose of deltamethrin

“…Insecticide bioassays were developed according to Pessoa et al (2015). Briefly, technical grade deltamethrin (99.1% -Bayer CropScience, Germany) was diluted in acetone P.A (Merck, Germany) producing a sublethal doses of use (3.4 and 3.8 ng/μl).…”