Monitoramento da suscetibilidade de populações de Triatoma sordida Stål, 1859 (Hemiptera: Reduviidae) ao inseticida deltametrina, na região Centro-Oeste do Brasil

Santos

Salazar

et al. 2015

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.

Section: Ethical Considerationssupporting

confidence: 87%

Section: Ethical Considerationsmentioning

confidence: 99%

Section: Ethical Considerationsmentioning

confidence: 99%

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

Santos

Salazar

et al. 2015

“…According to Obara et al 12 , there are no records of Brazilian T. sordida populations resistant to deltamethrin. A susceptibility study of 11 populations from the center-west region of Brazil revealed RR 50 values ranging from 1.05 to 1.48.…”

Section: Discussionmentioning

confidence: 99%

Deltamethrin pyrethroid susceptibility characterization of Triatoma sordida Stål, 1859 (Hemiptera: Reduviidae) populations in the Northern Region of Minas Gerais, Brazil

Dias

Diotaiuti

2014

Introduction:Triatoma sordida is the most captured Triatomine species in the Brazilian artifi cial environment. In 2008, the discovery of three Triatomine populations with altered susceptibilities to deltamethrin highlighted the importance of investigating the genetic potential for resistance in triatomines. The purpose of this study was to characterize the susceptibility to deltamethrin of peridomestic T. sordida populations in Minas Gerais, Brazil. Methods: A susceptibility reference lineage derived from Uberaba, Minas Gerais, Brazil was used. Serial dilutions of deltamethrin were prepared and applied to the dorsal abdomen of fi rst instar nymphs. The control group received only pure acetone. Mortality was evaluated after 72h. Qualitative tests assessed mortality in response to a diagnostic dose of 1xLD 99 of the susceptibility reference lineage. Results: Susceptibility profi le characterization of T. sordida populations revealed resistance ratios (RR 50 s) ranging from 0.42 to 3.94. The percentage mortality in response to the diagnostic dose varied from 70% to 100%. A comparison of the results obtained in the quantitative and qualitative assays demonstrated a lack of correspondence for some populations. Conclusions: We demonstrated that only T. sordida populations that present a RR 50 >1.0 have altered susceptibility, and the execution of simultaneous fi eld and laboratory tests is required to understand the actual effect of vector control. A possible cause of the observed resistance ratios might be the continuous use of pyrethroids in Brazil since the 1980s.

“…The RR is calculated from SRL lethal doses; thus, the resistance level obtained may consequently interfere, in the future developments to be adopted by the managers involved with Triatominae control in the fi eld. As an example, the RR 50 observed by Obara et al (51) for T. sordida populations treated with deltamethrin allowed the study population to be classifi ed as susceptible to the tested insecticide, leading to the recommendation of time line monitoring. However, if the authors had used the SRL adopted by Pessoa (31) , the RR 50 would have increased nine fold.…”

Section: Methodological Difficultiesmentioning

confidence: 99%

History of insecticide resistance of Triatominae vectors

Viñas²,

Rosa

et al. 2015

In the last 15 years, different types of Triatominae resistance to different insecticides have been reported; thus, resistance may be more widespread than known, requiring better characterization and delimitation, which was the aim of this review. This review was structured on a literature search of all articles from 1970 to 2015 in the PubMed database that contained the keywords Insecticide resistance and Triatominae. Out of 295 articles screened by title, 33 texts were selected for detailed analysis. Insecticide resistance of Triatomines is a complex phenomenon that has been primarily reported in Argentina and Bolivia, and is caused by different factors (associated or isolated). Insecticide resistance of Triatominae is a characteristic inherited in an autosomal and semi-dominant manner, and is polygenic, being present in both domestic and sylvatic populations. The toxicological profi le observed in eggs cannot be transposed to different stages of evolution. Different toxicological profi les exist at macro-and microgeographical levels. The insecticide phenotype has both reproductive and developmental costs. Different physiological mechanisms are involved in resistance. Studies of Triatomine resistance to insecticides highlight three defi ciencies in interpreting the obtained results: I) the vast diversity of methodologies, despite the existence of a single guiding protocol; II) the lack of information on the actual impact of resistance ratios in the fi eld; and III) the concept of the susceptibility reference lineage. Research on the biological and behavioral characteristics of each Triatominae species that has evolved resistance is required in relation to the environmental conditions of each region.