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Researchers Find A Way To Turn Off Mosquitoes Love For Human Scent
May 31, 2013
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"If a mosquito has a soul, it is mostly evil." - Douglas Hofstadter, American professor of cognitive science

That quote probably sums up how a lot of you feel about mosquitoes, especially with summer nearly here.

But imagine this - what if mosquitoes could be thrown off the scent of their prey? In other words, us.

Well, researchers at the Howard Hughes Medical Institute in Maryland have found a way to alter the little bloodsuckers' sense of smell, by switching off a gene.

Of course, in this country, mosquitoes are mostly annoying. But in many parts of the world, they carry diseases such as malaria and dengue fever, which kills hundreds of thousands of people each year.

According to the U.S. Centers for Disease Control, in 2010 an estimated 219 million cases of malaria occurred worldwide and 660,000 people died, the majority in Africa.

In 2007, researchers at the Hughes Institute studied the Aedes aegypti, the type of mosquito that transmits dengue and yellow fever.

When given a choice between a human meal or any other animal, a normal Aedes aegypti's prefers us. Same goes for the Anopheles gambiae, which carries the malaria virus.

"They love everything about us," said Leslie Vosshall, a neurobiologist who led this latest study.

"They love our beautiful body odour, they love the carbon dioxide we exhale and they love our body heat," she told

However, the researchers found that by switching off a gene called orco and creating mutant mosquitoes, with no sense of smell, the bugs had a tough time distinguishing people from animals.

"We knew this gene was important for flies to be able to respond to the odors they respond to," said Vosshall. "And we had some hints that mosquitoes interact with smells in their environment, so it was a good bet..."

"By disrupting a single gene, we can fundamentally confuse the mosquito from its task of seeking humans," she said.

A California technician sprays for West Nile.

The team also looked at DEET, which is designed to keep mosquitoes away.

They tested whether genetically engineered mosquitoes responded differently to the spray-on repellent. They exposed these mosquitoes to:

1. Human arms with 10% DEET
2. Untreated, control group arms.

The little vampires showed no preference, leading the researchers to conclude the mosquitoes couldn't smell the DEET.

However, they did quickly fly away from the arms sprayed with DEET.

"This tells us that there are two totally different mechanisms that mosquitoes are using to sense DEET," Vosshall said. "One is what's happening in the air, and the other only comes into action when the mosquito is touching the skin."

Scientists have long believed that smell was a key factor in how mosquitoes hunt, as well as body heat and the release of carbon dioxide.

They hope this discovery will help them find better ways to fight diseases carried by mosquitoes and develop better repellants.

The idea is to change mosquitoes taste preferences, rather than killing them off because that would throw off the ecosystem's delicate balance.

The study is published in the journal, Nature.



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