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, 8 (2), e54438

Aedes Aegypti Mosquitoes Exhibit Decreased Repellency by DEET Following Previous Exposure

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Aedes Aegypti Mosquitoes Exhibit Decreased Repellency by DEET Following Previous Exposure

Nina M Stanczyk et al. PLoS One.

Abstract

DEET (N,N-Diethyl-m-toluamide) is one of the most widely used mosquito repellents. Although DEET has been shown to be extremely effective, recent studies have revealed that certain individual insects are unaffected by its presence. A genetic basis for this has been shown in Aedes aegypti mosquitoes and the fruit fly Drosophila melanogaster, but, for the triatomine bug, Rhodnius prolixus, a decrease in response to DEET occurred shortly after previous exposure, indicating that non-genetic factors may also be involved in DEET "insensitivity". In this study, we examined host-seeking behaviour and electrophysiological responses of A. aegypti after pre-exposure to DEET. We found that three hours after pre-exposure the mosquitoes showed behavioural insensitivity, and electroantennography revealed this correlated with the olfactory receptor neurons responding less to DEET. The change in behaviour as a result of pre-exposure to DEET has implications for the use of repellents and the ability of mosquitoes to overcome them.

Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. Behavioural repellency on second exposure.
Proportion of female Aedes aegypti mosquitoes probing in response to a treatment on first exposure (treatment 1) or to a second treatment after pre-exposure to a treatment 3 hours previously (treatment 1/treatment 2). Treatments were A: a control arm (CA) (0.5 ml ethanol), a DEET treated arm (DA) (0.5 ml, 20% in ethanol); B: a hemotek heating device with nylon control (H) (0.5 ml hexane), a hemotek device with nylon spotted with DEET (HD) (0.5 ml, 20% in redistilled hexane); C: a section of nylon spotted with DEET with no other stimulus (D). Means are ± SEM. Means with different letters are significantly different from each other (p<0.05).
Figure 2
Figure 2. Olfactory responses of DEET-sensitive and insensitive mosquitoes.
EAG responses of female Aedes aegypti showing behavioural DEET-sensitivity (s) or DEET-insensitivity (i) in experiment 1. Mosquitoes of unknown DEET-sensitivity (s+i) were collected from cages tested with a control arm. DEET-insensitive females were collected from cages tested with DEET on an arm (DA), tested first with a control arm and then DEET on an arm (CA/DA), and tested with DEET on an arm then retested with DEET on an arm (DA/DA). DEET-sensitive mosquitoes were also collected from cages tested with DEET on an arm and then retested with DEET on an arm (DA/DA). Means are ± SEM. Means with different letters are significantly different from each other (p<0.05).

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