Electroantennographic and Behavioral Evidence Identifies Carvone and IR3535 as Biting Deterrents Against Rhodnius...

Electroantennography (EAG) is a valuable approach for monitoring insect antennal responses to insecticidal and test compounds and may provide a preliminary screening method for identifying compounds with potential activity against medically important insect vectors. The objective of this study was to evaluate the EAG responses of Rhodnius prolixus to different xenobiotics and to compare these electrophysiological responses with host approach and protection against biting. Antennae from adult triatomines subjected to prolonged fasting (≥30 days) were exposed to the tested compounds. In parallel, live-bait behavioral bioassays were conducted using Gallus gallus and a newly designed laboratory device. Exposure to IR3535 and carvone produced a greater than 60% reduction in ammonia-induced EAG amplitude, consistent with the protection times observed in the behavioral assays (135.6 ± 43.29 min and 108.0 ± 26.33 min, respectively). These findings indicate that IR3535 and carvone alter antennal responses to ammonia and provide prolonged protection against R. prolixus bites. Because neither compound significantly delayed host approach, the observed behavioral effect was more consistent with biting deterrence than with demonstrated spatial repellency. EAG may therefore serve as a preliminary complementary screening approach, although its ability to identify compounds that interfere with hematophagous feeding requires further validation using larger and chemically diverse compound libraries.