Focal resistance to organosynthetic insecticides in Aedes aegypti (Linneaus, 1762) (Diptera: Culicidae) from different municipalities in Aragua state, Venezuela.

In the present study the levels of resistance to insecticides in larvae of Aedes aegypti were determined in three municipalities of Aragua state, Venezuela (Girardot, Mario Briceno Iragorri and Urdaneta), in comparison with a susceptible strain (Rockefeller), through the WHO method of immersion. The organophosphorous insecticides (methyl malathion, pirimiphos methyl and temephos) and the carbamate (propoxur) were evaluated. Malathion resistance was found in the three strains, with values of FR50 69.50x, 113.52x and 150.6x to the strains from Girardot, Mario Briceno Iragorri and Urdaneta respectively, suggesting that differences in the levels of resistance to this insecticide, is a phenomenon of focal nature. All strains were susceptible to the organophosphate pirimiphos methyl, temephos and the carbamate propoxur. Studies with synergists PB and DEF showed that the enzymes in the group multifunction oxidases are involved in the development of resistance to malathion. The results provide reference information on the behavior of the strains compared with insecticides during the period of study and should be considered for the implementation of strategies for managing and monitoring of insecticide resistance locally.