VOA慢速英语2014 科学家们寻找新的方法来对付蚊子（在线收听）

AS IT IS 2014-05-25 Scientists Search for New Ways to Stop Mosquitoes 科学家们寻找新的方法来对付蚊子

The sound of a mosquito can mean trouble in many parts of the world.  The bite of a mosquito can be deadly. Today, we will hear about some of the diseases these insects carry and what scientists are doing to help protect people.

We begin with one of the most common diseases linked to mosquitoes: malaria.  The World Health Organization estimates that almost 630,000 people died from malaria and malaria-related causes in 2012.  Most of these cases were in African countries south of the Sahara Desert. 

In the United States, scientists are seeking new ways to fight malaria.  A group of California researchers is working to develop more effective and less costly ways to protect people from mosquitoes.  The researchers work at the University of California Riverside.  They are investigating mosquitoes’ sense of smell.  They found the insects use the same receptor for identifying carbon dioxide in human breath as they do for the smell of our skin.  

Anandasankar Ray is leading the investigation.  He says scientists tested more than a million chemical compounds until they found a substance called Ethyl pyruvate.  He says Ethyl pyruvate makes the mosquito’s receptor inactive.

“When we apply Ethyl pyruvate to a human arm and offer it to the mosquitoes -- hungry mosquitoes in a cage -- then very few of the mosquitoes are attracted to the human arm because only a few of them are able to smell it out.”

Genevieve Tauxe is a member of the UC Riverside research team.  She says it was not easy to find the neurons, or nerve cells, that recognize both the smell of human breath and skin.  She describes a device the researchers are using to examine mosquitos.

“With this apparatus, we’re able to insert a very small electrode into the part of the mosquito's nose, effectively, where it’s olfactory neurons are and where the smell is happening.”

The scientists use these instruments to look for the signals that a mosquito's neurons send to its brain when it finds an interesting smell.  Computer screen images show when the sense is strong or weak. 

Anandasankar Ray says a product based on Ethyl pyruvate may cost less to manufacture than DEET, the most effective chemical treatment now in use.  He says DEET is too costly for most people who live in areas affected by malaria. 

“Perhaps by finding odors that can attack other target receptors, we will be able to improve upon DEET and finally have the next generation of insect behavior control products.”

The scientists believe they will soon be able to find a way to manufacture less costly and more effective products for the fight against mosquitoes.  

I'm Jonathan Evans in Washington.