Newly found natural odours could pave way for developing mosquito repellents

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London, Aug 27 (ANI): In a lab study on fruit flies, entomologists led by an Indian origin scientist at the University of California, Riverside, have discovered a novel class of compounds that could help in developing inexpensive and safe mosquito repellents for combating West Nile virus and other deadly tropical diseases.

Under stress, fruit flies emit carbon dioxide (CO2) that serves as a warning to other fruit flies that danger or predators could be nearby.

The fruit flies are able to detect the CO2 and escape because their antennae are equipped with specialized neurons that are sensitive to the gas.

But fruits and other important food sources for fruit flies also emit CO2 as a by-product of respiration and ripening.

Researchers started to wonder how does fruit flied find their way to these foods, despite having an inherent tendency to avoid CO2.

However, Anandasankar Ray, an assistant professor in the Department of Entomology, and Stephanie Turner, his graduate student, have now identified a new class of odorants - chemical compounds with smells - present in ripening fruit that prevent the CO2-sensitive neurons in the antennae from functioning.

They discovered that particularly two odours, hexanol and 2,3- butanedione, are strong inhibitors of the CO2-sensitive neurons in the fruit fly.

The research has strong implications for control of deadly diseases transmitted by Culex mosquitoes such as West Nile virus disease and filariasis, an infectious tropical disease affecting the lymphatic system.

"CO2 emitted in human breath is the main attractant for the Culex mosquito to find people, aiding the transmission of these deadly diseases. In our experiments we identified hexanol, and a related odor, butanal, as strong inhibitors of CO2-sensitive neurons in Culex mosquitoes. These compounds can now be used to guide research in developing novel repellents and masking agents that are economical and environmentally safe methods to block mosquitoes' ability to detect CO2 in our breath, thereby dramatically reducing mosquito-human contact," Nature quoted Ray as saying.

Inhibitory odours not only play an important role in modifying insect behaviour, but the study found that some of these odours even have a long-term effect.

For example, the researchers found that some odours silenced the CO2 neuron in the fruit fly well beyond the period of application.

"To our surprise, we found that exposure to a long-term CO2 response inhibitor can exert a profound and specific effect on the behavior of the insect, even after the inhibitor is no longer in the environment.

This means this odorant could potentially be used to keep mosquitoes at bay for longer periods of time, benefiting people in areas where mosquito-transmitted diseases are prevalent," said Ray.

The results of the study appear in Nature. (ANI)

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