This blog is intended to go along with Population: An Introduction to Concepts and Issues, by John R. Weeks, published by Cengage Learning. The latest edition is the 12th (it came out in 2015), but this blog is meant to complement any edition of the book by showing the way in which demographic issues are regularly in the news.

If you are a user of my textbook and would like to suggest a blog post idea, please email me at: john.weeks@sdsu.edu

Monday, December 9, 2013

Staying off a Mosquito's Radar Screen

If you are never bitten by an infected mosquito, you won't get malaria. That seems pretty simple. The trick, though, is to avoid being bitten, which is not easy in places infested with mosquitos. Bed nets and repellents are good preventive measures, but what is it that repels mosquitos? Researchers at the University of California, Riverside have been working on that problem, but from the opposite angle. What smells attract mosquitos, so that we can avoid them? The answer was published in the journal Cell:
Female mosquitoes that transmit deadly diseases locate human hosts by detecting exhaled CO2 and skin odor. The identities of olfactory neurons and re- ceptors required for attraction to skin odor remain a mystery. Here, we show that the CO2-sensitive olfactory neuron is also a sensitive detector of human skin odorants in both Aedes aegypti and Anopheles gambiae. We demonstrate that activity of this neuron is important for attraction to skin odor, establishing it as a key target for intervention.
Note that the Anopheles gambiae is the mosquito that tends the carry the particularly deadly plasmodium falciparum parasite in sub-Saharan Africa. A story in today's San Diego Union-Tribune decodes some of the scientific jargon:
Mosquitoes use carbon dioxide in exhaled breath to sense that people are near. But when they get close to a person, the bloodsucking disease-carriers ignore CO2 and hone in on skin odors to find a fleshy landing strip. Skin emits hundreds of chemicals into the air. Even sweaty socks will attract mosquitoes. How this mechanism works was a mystery.
The new study identified the cells that detect skin odors, along with chemicals that block the most important skin odors. Researchers also found pleasant-smelling attractants that can serve as decoys.
As is true with most such research, there is a still a lot of work to do before these decoy scents hit the market, but every little battle against mosquitos is worth it in terms of lives saved.

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