DEET as a feeding deterrent

Abstract

The insect repellent N,N-diethyl-3-methylbenzamide (DEET), is a multimodal compound that acts as a spatial repellent as well as an irritant (contact repellent), thus being perceived by the insect’s olfactory and gustatory systems as an odorant and a tastant, respectively. Soon after DEET was developed, almost 6 decades ago, it was reported that it reduced mosquito feeding on blood mixed with this repellent. It is now known that the mosquito proboscis senses contact repellents with the tips (labella) of the labium, which remain in direct contact with the outer layers of the skin, while the stylets, including the feeding deterrent sensor (labrum), penetrate the skin. We designed a behavioral assay that allowed us to tease apart contact repellency from feeding deterrence. First, we demonstrate here that when DEET was mixed with blood and covered by Parafilm® layers, it did not leak to the outer surface. In our assays, the mean number of landings and duration of contacts with surfaces covering blood mixed with DEET or blood plus solvent (dimethyl sulfoxide) did not differ significantly. The feeding times, however, were significantly different. When blood was mixed either with 0.1 or 1% DEET, female southern house mosquitoes spent significantly less time feeding than the time spent feeding on blood mixed only with the solvent. By contrast, there were no significant differences in the mean times of feeding on blood containing 1% picaridin and blood plus solvent. Like DEET, the contact repellent and insecticide, permethrin, caused a significant reduction in feeding time. We, therefore, concluded, that in this context, DEET and permethrin act as feeding deterrents.

Aedes aegypti Mosquitoes Use Their Legs to Sense DEET on Contact

“…In contrast, DEET completely inhibited blood feeding on contact (Figure 1K). These results support our conclusions from the arm-in-cage experiments in Figures 1E and 1F and agree with recent findings from Culex quinquefasciatus mosquitoes, which demonstrated that animals spent less time feeding on Parafilm-covered blood-soaked cotton balls if DEET was mixed into the blood [11]. These data support the hypothesis that DEET is bitter by ingestion, but its bitterness per se does not explain its highly effective contact chemorepellency.…”

“…DEET (N, N-diethyl-meta-toluamide) is the most effective and widely used insect repellent, but its mechanism of action is both complex and controversial [1]. DEET acts on insect smell [2][3][4][5][6] and taste [7][8][9][10][11], and its olfactory mode of action requires the odorant coreceptor orco [2,3,6]. We previously observed that orco mutant female Aedes aegypti mosquitoes are strongly attracted to humans even in the presence of DEET, but they are rapidly repelled after contacting DEET-treated skin [6].…”

DEET feet: Aedes aegypti mosquitoes use their tarsi to sense DEET on contact

“…1J). These results agree with recent findings from Culex quinquefasciatus mosquitoes, which demonstrated that animals spent less time feeding on Parafilm-covered blood-soaked cotton balls if DEET was mixed into the blood [11]. These data support the hypothesis that contact DEET repellency is independent of bitter taste, and that an unknown, sensory mechanism repels Ae.…”

“…

DEET (N, N-diethyl-meta-toluamide) is the most effective and broadly used insect repellent, but its mechanism of action is both complex and controversial [1]. Previous work demonstrated that DEET acts both on insect smell [2][3][4][5][6] and taste [7][8][9][10][11] systems. Its olfactory mode of action requires the odorant co-receptor orco [2, 3, 6], while its gustatory repellency is mediated by activation of bitter taste receptors and neurons in the proboscis upon ingestion [8].

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Multiple channels of DEET repellency in Drosophila

“…DEET has been reported to function as a feeding deterrent. 23,24,[42][43][44] Gr32a, Gr33a and Gr66a are widely expressed in bitter-sensing neurons, and are thought to be necessary for DEET repellence. 23 However, expression of these three gustatory receptors in sweet-sensing neurons failed to result in DEET sensitivity, implying that there are additional components remaining to be uncovered.…”