VOA常速英语:Promising Mosquito Repellent Announced

In many regions of the world, mosquitoes are a seasonal pest. In other regions, they carry serious diseases like malaria. The World Health Organization estimates that almost 630,000 people died of malaria-related causes in 2012, mostly in Sub-Saharan Africa.  Now, a group of U.S.-based scientists is working to develop a more effective and less expensive mosquito repellent than currently in use.  
 
The research, at the University of California Riverside, is based on the fact that mosquitoes use the same receptor for detecting carbon dioxide in our breath as they do for the odor from our skin when they come closer.
 
The lead investigator, Anandasankar Ray, says scientists tested more than a million chemical compounds until they found a substance called Ethyl pyruvate that shuts down the mosquitoes’ receptor.
 
“When we apply Ethyl pyruvate to a human arm and offer it to 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," said Ray.
 
Genevieve Tauxe, also on the team, says finding the mosquito neurons that detect both our breath and skin odor was not easy.
 
“With this apparatus, we are able to insert a very small electrode into the part of the mosquito's nose, effectively, where its olfactory neurons are and where the smell is happening," said Tauxe.
 
With these instruments, scientists were able to detect the signals that a mosquito’s neurons send to its brain when it senses attractive odors.  Spikes on the computer screen show when the attraction is strong or weak.
 
Ray says a repellent based on Ethyl pyruvate may be cheaper to manufacture than DEET, the most effective chemical now in use. He says it's too expensive for most people in malaria-affected areas.
 
"Perhaps by finding designer odors, better 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 product," he said.
 
The University of California scientists say they believe they will soon be able to find a way to manufacture cheaper and more effective repellents for the fight against mosquitoes.