Thursday, February 21, 2013

PLoS One: Mosquitoes Less Deterred By DEET After Previous Exposure



# 6954



In May of 2010 in  From the `Nature Bats Last’ Dept, we looked at a PNAS study by James Logan et al. that looked at the reasons behind the small but growing number of mosquitoes that are not repelled by DEET - or N,N-Diethyl-m-toluamide.

Among some specially bred female Aedes aegypti mosquitoes, researchers found resistance to DEET to be caused by a single dominant gene, one that could be passed down to subsequent generations even if inherited from one parent.


Today, these same researchers are back with a new study that finds it doesn’t require a genetic change to reduce a mosquito’s susceptibility to DEET, all it really takes is time.


Roughly three hours.



Aedes aegypti Mosquitoes Exhibit Decreased Repellency by DEET following Previous Exposure

Nina M. Stanczyk, John F. Y. Brookfield, Linda M. Field, James G. Logan


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.



Follow the link to read the entire open-access study.  How long this acquired `resistance’ lasts in an exposed mosquito has not been determined.


Coming off a near-record setting year for West Nile Virus infections in the United States (see DVBID: Final West Nile Report For 2012), and with the continued  global spread of Dengue, Chikungunya, Malaria, Yellow Fever and other mosquito-borne pathogens, mosquito repellants are an important disease preventative.


In a press release from the Public Library of Science,  lead author James Logan explains further:


Mosquitoes exposed to DEET once are less repelled by it a few hours later


"Our study shows that the effects of this exposure last up to three hours. We will be doing further research to determine how long the effect lasts", says Logan.


He adds, "This doesn't mean that we should stop using repellents - on the contrary, DEET is a very good repellent, and is still recommended for use in high risk areas. However, we are keeping a close eye on how mosquitoes can overcome the repellent and ways in which we can combat this."

No comments: