Monitoring the Resistance of Triatominae (Hemiptera: Reduviidae) To Insecticides
  Key Words  
  Deltamethrin, Triatoma brasiliensis, Triatoma sordida,Topical bioassays.
  Marcos Takashi Obara, Jose Maria Soares Barata and Rodrigo Gurgel Goncalves
  Currently, there is evidence of Triatoma infestans Klug, 1834 populations from southern Bolivia and northern Argentina with high levels of resistance to pyrethroids. In this study we characterized the susceptibility levels of 37 Triatominae populations to deltamethrin. The bioassays were performed by topical application of insecticides in the abdomen of 1st stage nymphs of Triatoma brasiliensis Neiva, 1911 and Triatoma sordida Stål, 1859 coming from the Northeast and Midwest regions of Brazil. Estimates of LD50 and RR50 of the different field populations showed high levels of susceptibility (LD50 <1 and RR50 <3) for all samples. It is suggested that the high spatial mobility of T. brasiliensis can be considered as the main obstacle to the selection of resistant individuals. The tests conducted showed that there is no need to replace the insecticide used in campaigns for vector control of Chagas disease in Brazil. However, temporal changes of susceptibility should be continuously monitored as well as the resistance mechanisms and their evolution in order to properly guide the actions of vector control.