VOA慢速英語(yǔ):科學(xué)家積極尋求新的方法阻止蚊蟲病害

00:00

00:00

MP3下載 文本下載

https://online2.tingclass.net/lesson/shi0529/0008/8694/as_it_is_201405252.mp3

https://image.tingclass.net/statics/js/2012

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

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

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

Anandasankar Ray is leading the investigation. He says scientists testedmore than a million chemical compounds until they found a substance calledEthyl pyruvate. He says Ethyl pyruvate makes the mosquito’s receptorinactive.

Mosquitoes can carry deadly diseases such as malaria.

“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 areattracted 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 saysit was not easy to find the neurons, or nerve cells, that recognize both thesmell of human breath and skin. She describes a device the researchers areusing 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 wherethe smell is happening.”

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

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

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

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

I'm Jonathan Evans in Washington.