Insecticide resistance in Brazilian Triatoma infestans and Venezuelan Rhodnius prolixus

Resistance levels to insecticides used in control of Chagas Disease vectors were assessed in two species of bugs (Hemiptera: Reduviidae): Triatoma inf estans (Klug) from Brazil and Rhodnius prolixus Stal from Venezuela. The re sistance ratios, compared to susceptible laboratory strains, were determine d by topical application bioassays. The T. infestans PA strain exhibited re sistance ratios of 7x to deltamethrin, 3.6x to beta-cyfluthrin and 3.3x to cypermethrin, but was susceptible to beta-cypermethrin and lambda-cyhalothr in. Rhodnius prolixus CA strain showed resistance to all the pyrethroids ev aluated, the resistance ratios ranging between 4.5x to lambda-cyhalothrin a nd 12.4x to cypermethrin. Deltamethrin resistance in both strains was decre ased by piperonyl butoxide, suggesting oxidative metabolism as cause of res istance.