Suscetibilidade de larvas de Aedes aegypti ao inseticida temefós no Distrito Federal Susceptibility of Aedes aegypti larvae to the insecticide temephos in the Federal District, Brazil

AbstractObjective To study the susceptibility status of Aedes aegypti to the organophosphate insecticidetemephos. Methods Samples of Ae. aegypti larvae were obtained, using ovitraps, from eight cities of theFederal District, central Brazil, in 2000 and 2001. Larvae were submitted to thediagnostic dose of 0.012 mg/l temephos, as recommended by standard World HealthOrganization methodology. Field populations were tested in parallel with referencestrains Rockefeller and DIVAL, from the Environmental Surveillance Directory (DIVAL)insectary. The concentration and purity of temephos solutions were verified by gaschromatography. Correlation calculations were performed using StatView – SASInstitute Inc., version 5. Student’s t test was used for detecting differences in susceptibility,with significance levels of α =0.05. Results In 2000, Ae. aegypti larvae populations from Taguatinga, Guara, and NucleoBandeirante showed resistance to temephos, with mortality ranging from 54.1 to63.4%. The populations from Gama, Planaltina, and Sobradinho showed alteredlevels of susceptibility (mortality ranging from 83.6 to 92.8%). The population fromCeilândia was the only susceptible one, with 98% mortality. In 2001, all populationstested were resistant (44.4 to 66.4% mortality). No significant correlation was foundbetween the susceptibility of populations and the distance between the cities of origin,or the amount of insecticide applied in the years preceding the study.