Abstract

Objectives:  To determine the resistance to organophosphate (temephos and malathion) and pyrethroid (deltamethrin, lambda cyhalothrin, and cypermethrin) insecticides in a strain of Aedes aegypti from Orotina.

Methods:  The evaluation of the resistance was carried out by larval bioassays. Lethal concentration 50% (LC50) was calculated for each insecticide. A factor of resistance 50% (FR50) was also calculated with respect to the Rockefeller strain, which served as susceptible control. In cases of resistance, the evaluation was replicated by exposing the larvae to piperonyl butoxide (PB), S, S, S tributylphosphorotritionate (DEF), and ethacrynic acid (AE), in order to establish the detoxification mechanisms associated with the resistance. In these cases, a factor of synergism 50% (FS50) was also calculated.

Results:  The Orotina strain of Ae. aegyptiwas susceptible to temephos, malathion, deltamethrin and lambda cyhalothrin, but showed incipient resistance to cypermethrin (LC50 = 0.01103 mg/L, FR50 = 5.32). Only PB reversed the state of resistance (FS50 = 10.92), which suggests a detoxification mechanism associated with the citochrome P450 monooxygenase system.

Discussion:  Although the Ae. aegyptistrain from Orotina showed resistance to cypermethrin, it was susceptible to other insecticides, which can be used as alternative options for chemical control of the vector. Conclusions: Monitoring of resistance is required to ensure the effectiveness of insecticides used in chemical control.

Key Words: dengue; insecticides; insecticide resistance; Aedes; vector control