Repellency of Eucalyptol and DEET Against Triatoma infestans, a Chagas Disease Vector: A Proof-of-Concept Study Under a Human Odor Background

Triatomines are vectors of Chagas disease. Control of Triatoma infestans, one of its main vectors, relies largely on the use of pyrethroid insecticides. However, due to resistance to them as well as environmental concerns, alternative control strategies are required. Here, we evaluated the volatile repellent activity of eucalyptol, carvacrol, carvone, and DEET (N, N-diethyl-3-methylbenzamide) under conditions that prevented the contact of the insects with the compounds, and under a human odor background, providing a realistic assessment of repellency for human protection. Importantly, eucalyptol and DEET were tested at low doses. Behavioral assays were conducted in a unidirectional olfactometer, mainly quantifying the following parameters: repellency coefficient (RC, 0 to 1 (1 = maximal repellency)) and biting inhibition. At 10 µL of pure compound, all chemicals induced strong and significant repellency (RC > 0.85). Eucalyptol and DEET remained highly effective at 1 µL (RC > 0.88) and continued to elicit significant repellency at 0.1 µL, whereas both compounds strongly inhibited biting behavior across the tested doses. Overall, our findings are a proof-of-concept suggesting that eucalyptol and DEET are highly effective volatile repellents and bite inhibitors against T. infestans, thus highlighting eucalyptol as a promising complementary alternative to DEET for human protection against Chagas disease.