Monitoring the susceptibility of Triatoma sordida Stål, 1859 (Hemiptera: Reduviidae) to deltamethrin insecticide, in Central-Western Brazil

Triatoma sordida Stål, 1859 populations were investigated for susceptibility to deltamethrin. This study aimed to analyze the resistance of 11 populations of insects from the States of Goiás, Mato Grosso and Mato Grosso do Sul by topical application bioassays. The estimated LD50 and RR50 showed high levels of susceptibility (LD50 < 1 and RR50 < 2). However, analysis of the slope of the dose response curve showed that the populations of insects in the towns of Firminópolis/GO, Posse/GO, Poxoréu/MT, Douradina/MS and Aparecida do Taboado/MS present great probability of evolving resistance and, thus, are more likely to tolerate treatment with deltamethrin. Small changes in susceptibility and low levels of resistance were detected, but the temporal changes of susceptibility should be continuously monitored to adequately guide the actions of vector-control of DC.