Mosquito-borne diseases such as malaria, dengue and yellow fever kill several million people every year and sicken hundreds of millions more.

Scientists have been working for years to stop these lethal diseases by either eliminating the disease-carrying mosquitoes or reducing the risk of the bug’s infectious bites.

Researchers know that only female mosquitoes feed on blood; they spread diseases by first obtaining a meal from an infected person and later biting an uninfected person.

A number of theories have been offered over the years as to how these mosquitoes find human hosts to bite and spread disease.

One vital clue that scientists are considering is that the mosquitoes use exhaled carbon dioxide as a way of zeroing in on their targets.  If that’s so, disrupting the carbon dioxide detection machinery of mosquitoes could halt the spread of diseases they transmit.

In a the recent issue of Nature, a team of scientists led by Anandasankar Ray, assistant professor of entomology at the University of California Riverside, says it has identified three classes of odor molecules that can severely damage, if not completely disrupt, the mosquitoes’ ability to detect carbon dioxide.

The mosquitoes’ carbon dioxide receptors are located in tiny, antennae-like appendages called maxillary palps which are close to the mouths of the mosquitoes.

With these receptors, mosquitoes are extremely sensitive to even the smallest changes in carbon dioxide concentrations, sensing the carbon dioxide in our breath from long distances.

Once they come near a plume of carbon dioxide plume, the mosquitoes orient themselves and fly upwind, eventually targeting in on us.

For their study, the scientists researched three of the deadliest species of mosquitoes: Anopheles gambiae, which spreads malaria, Aedes aegypti, the vector that spreads dengue and yellow fever, and Culex quinquefasciatus, the species that spreads filariasis and West Nile virus.

The three classes of the odor molecules are:

> Inhibitors: Odor molecules, like hexanol and butanal, that inhibit the carbon dioxide receptor in mosquitoes and flies.

> Imitators: Odor molecules, like 2-butanone, that mimic carbon dioxide and could be used as lures for traps to attract mosquitoes away from humans.

> Blinders: Odors molecules, like 2,3-butanedione, that cause ultra-prolonged activation of the carbon dioxide sensing neurons, effectively “blinding” the mosquitoes and disabling their carbon dioxide detection machinery for several minutes.

The researchers point to the many advantages that these chemicals can offer in reducing mosquito-human contact, it’s thought that these findings can lead to the development of new generations of insect repellents and lures.

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