Tuesday, November 1, 2011

Mosquito Bred to Fight Dengue Fever Shows Promise in Study

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By Reg Gale - Oct 31, 2011 8:17 PM GMT+0700

Scientists attempting to halt Dengue fever have, for the first time, released mosquitoes into the wild that were genetically modified to pass on deadly DNA that kills their offspring.

About 19,000 lab-altered insects were cast loose on 25 acre of land on Grand Cayman Island in 2009, according to a report yesterday in the journal Nature Biotechnology. Later tests showed they made up about 16 percent of the mosquito population, and that the fatal gene was carried by about 10 percent of larvae. Scientists said the modified insects -- all males -- were about half as successful in mating as normal.

There are as many as 100 million cases of Dengue reported each year worldwide, making it one of the most medically significant viruses carried by mosquitoes, the report said. There’s no vaccine, boosting the need to limit the insects that carry it, the researchers said. The experiment, by scientists from closely held Oxitec Ltd., a biotechnology company based in Oxford, England, has spurred concern that there may be unintended environmental consequences.

The study was designed ``to allow us tentatively to estimate how many mosquitoes might need to be released in this area to suppress the target population,” the researchers said.

Use of genetically enhanced mosquitoes was discussed in a series of articles in the magazine Scientific American this month. In those reports, Helen Wallace, director of GeneWatch UK, said she was concerned the new form of insect becomes part of a complex system involving predators and prey that scientists have no control over.

2010 Report

Wallace cited a 2010 report by the European Food Safety Authority that raised the potential for illnesses to evolve into more dangerous forms, and for other insects to move into the ecological niche created by the absence of mosquitoes.

In the Grand Caymans study, the scientists said the percentage of successful couplings by the altered mosquitoes may have been limited because they didn’t fit easily into the insect social system, or by the physical effects of handling and distributing them. The genetic changes may also have had a physical impact on some of the insects, they said.

Dengue fever, most common in the tropics, causes high fever, headache and rash, along with severe joint and muscle pain.

Oxitec developed the technology, which the Mosquito Research and Control Unit, backed by the Cayman Islands government, implemented for the study, Oxitec Chief Executive Officer Hadyn Parry said in an interview.

To contact the reporter on this story: Reg Gale at rgale5@bloomberg.net.

To contact the editor responsible for this story: Reg Gale at rgale5@bloomberg.net.

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