Mosquitoes can spread a range of potentially life-threatening diseases. Existing methods of controlling the insect can be inefficient. For example, mosquitoes can develop a resistance to insecticides(杀虫剂).

Now, Kevin Gorman at the biotechnology firm Oxitec in Abingdon, UK, and his colleagues have genetically modified (基因改造) males of the mosquito species Aedes aegypti in a way that will greatly cut the insect’s population. Among all mosquito species, only females bite. So the team modified males to create so-called OX5034 mosquitoes. They have a gene that allows young male mosquitoes to live, but prevents the females from surviving into adulthood.

In the peak season for reproducing, OX5034 males were released into four heavily populated places in the city of Indaiatuba in Brazil. Within two of these neighborhoods, 100 modified mosquitoes were released at a time, while the remaining test areas were exposed to up to 500 of the insects at a time. Compared with a nearby community that wasn’t exposed to any of these mosquitoes, the places where the modified insects were released saw an 88 percent to 96 percent decline in their mosquito population.

The researchers particularly focus on controlling dengue-a disease caused by a virus carried by mosquitoes. Globally, the number of dengue cases has grown significantly in the past three decades, with 100 million to 400 million cases now occurring annually. While the study didn’t look at whether suppressing (抑制) the mosquitoes led to a lower rate of dengue, there was evidence of this elsewhere. Similar efforts in Australia saw fewer cases of locally spread dengue compared with previous years. A study also found a 77 percent reduction of dengue in Indonesia after modified mosquitoes were introduced there.

According to Dawn Wesson at the Tulane University School of Public Health and Tropical Medicine, Louisiana, Oxitec’s effort is a step up from previous insect control strategies in which mosquito sexual selection wasn’t done by genetic means. That’s the beauty of this method. As well as dengue, Oxitec is making plans for developing modified mosquitoes to reduce other diseases like malaria, says Nathan Rose at Oxitec.

【小题1】How does Kevin Gorman’s team try to control mosquitoes?

A．By decreasing the males’ population.

B．By transforming all mosquitoes’ genes.

C．By shortening the females’ life.

D．By improving the insecticides’ effect.

【小题2】Which aspect of the research is mainly discussed in paragraph 3?

A．The target and site.	B．The process and findings.
C．The data and report.	D．The preparations and methods.

【小题3】Why are Australia and Indonesia mentioned in paragraph 4?

A．To state the potential use of the method.

B．To explain the background of the study.

C．To draw attention to the severity of dengue.

D．To show the method’s effect on reducing dengue.

【小题4】What may Oxitec work on next?

A．Widening the applications of the method.

B．Engineering other species of mosquitoes.

C．Exploring better mosquito control strategies.

D．Finding cures for mosquito-related diseases.