Aerobic Metabolism Alterations as an Evidence of Underlying Deltamethrin Resistance Mechanisms in Triatoma infestans (Hemiptera: Reduviidae)

Abstract

Triatoma infestans (Klug, 1834), the main vector of Chagas disease in Latin America, is regularly controlled by sprayingthe pyrethroid deltamethrin, to which some populations have developed resistance. The three main mechanisms ofresistance are 1) metabolic resistance by overexpression or increased activity of detoxifying enzymes, 2) target sitemutations, and 3) cuticle thickening/modification. We use open-flow respirometry to measure real-time H2O loss rate(V˙ H2O) and CO2 production rate (V˙ CO2), on nymphs from susceptible and resistant populations before and after exposure to the insecticide to understand the underlying mechanisms of resistance in live insects. Lack of differencesin V˙ H2O between populations suggested that cuticular thickness/composition is not acting as a relevant resistancemechanism. Similarly, there was no difference in resting V˙ CO2, suggesting a trade-off between resistance mechanisms and other physiological processes. The increment in V˙ CO2 after application of deltamethrin was similar in bothpopulations, which suggested that while enhanced enzymatic detoxification may play a role in resistance expressionin this population, the main mechanism involved should be a passive one such as target site mutations. Open-flowrespirometry provided useful evidence for evaluating the mechanisms involved in deltamethrin resistance. Using thistechnique could improve efficiency of scientific research in the area of insecticide resistance management, leading toa faster decision making and hence improved control results.