Reduced effectiveness of repellents in a pyrethroid-resistant strain of Aedes aegypti (Diptera: culicidae) and its correlation with olfactory sensitivity

Authors: YANG, LIU - University Of Florida; NORRIS, EDMUND - University Of Florida; JIANG, SHIVAO - University Of Florida; Bernier, Ulrich; Linthicum, Kenneth - Ken; BLOOMQUIST, JEFFREY - University Of Florida

Submitted to: Pest Management Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/21/2019
Publication Date: 7/24/2019
Citation: Yang, L., Norris, E.J., Jiang, S., Bernier, U.R., Linthicum, K., Bloomquist, J.R. 2019. Reduced effectiveness of repellents in a pyrethroid-resistant strain of Aedes aegypti (Diptera: culicidae) and its correlation with olfactory sensitivity. Pest Management Science. https://doi.org/10.1002/ps.5562.
DOI: https://doi.org/10.1002/ps.5562

Interpretive Summary: BACKGROUND: The mosquito, Aedes aegypti (Diptera: Culicidae), is the primary vector of a number of serious human diseases caused by the dengue, Zika, chikungunya, and yellow fever viruses. Mosquito resistance to insecticides and repellents are becoming a serious problem in protecting people where these diseases are transmitted. We assessed the behavior of resistant and susceptible Aedes aegypti mosquitoes to three contact repellent standards: N, N-diethyl-3-methylbenzamide (DEET), ethyl 3-[acetyl(butyl)amino] propanoate (IR3535), and 2-undecanone, as well as to a pyrethrum extract and the spatial repellent transfluthrin. We also investigated the sensitivities to these compounds to the mosquitoes, as measured by nerve activity when their antennae where were exposed. Compared to the susceptible mosquitoes resistant mosquitoes were resistant to DEET and even more resistant to IR3535. Resistance was also observed to the pyrethrum extract and transfluthrin. The measured amount of nervous activity in the antennae were consistent with their behavioral effects. This work highlights the need for understanding the development of pesticide resistances in mosquitoes, and the importance of finding alternative strategies to control resistance development.

Technical Abstract: BACKGROUND: The mosquito, Aedes aegypti (Diptera: Culicidae), is the primary vector of dengue fever, Zika, chikungunya, and yellow fever. While the repeated use of chemical control measures has brought about serious resistance problems, insecticides and repellents are still major tools for vector control. Behavioral performance was assessed in 15, 30, and 60 min exposures to three contact repellent standards: N, N-diethyl-3-methylbenzamide (DEET), ethyl 3-[acetyl(butyl)amino] propanoate (IR3535), and 2-undecanone, as well as pyrethrum extract and transfluthrin in susceptible (Orlando) and a pyrethroid-resistant Puerto Rico strain of Aedes aegypti. Additionally, we investigated the sensitivities to these compounds in electroantennographic studies. RESULTS: Different levels of resistance were found to all the tested insect repellents on the Puerto Rico strain of Ae. aegypti when compared with the susceptible Orlando strain. Resistance ratios at the different time points varied from 2.1-2.3 for DEET and 11.6-12.7 for IR3535 in the Puerto Rico strain of Ae. aegypti. With 2-undecanone, concentrations >100 µg/cm2 were toxic, so accurate resistance ratios could not be determined. Resistance was also observed to pyrethrum extract and transfluthrin in behavioral response. Electrophysiological tests found decreased antennal sensitivity to these chemical repellents consistent with their behavioral effects. CONCLUSION: The reduced sensitivity to these repellents presumably represents a fitness cost arising from the kdr mutation present in Puerto Rico Aedes aegypti. This work highlights the need for understanding collateral effects from the evolution of pesticide resistances in mosquitoes, and the importance of finding alternative strategies to control resistance development.