Saving Lives with Genetically Engineered Mosquitoes
It's common to release sterilized males as a means of reducing mosquito populations and preventing human disease. But it didn't work for Aedes aegypti mosquitoes, which spread dengue and yellow fever. So Nature reports today that genetic engineering has proved a successful alternative.
GM mosquitoes wipe out dengue fever in trial - November 11, 2010
The controlled release of male mosquitoes genetically engineered to be sterile has successfully wiped out dengue fever in a town of around 3000 people, in Grand Cayman, an island in the Caribbean Sea, researchers report.
The release is the first field trial of GM dengue-carrying mosquitoes (Aedes aegypti) developed by scientists at Oxitec, a UK-based company founded and part-owned by the University of Oxford. (You can see a video of the release here.) The researchers reported the findings of the study, which ran from May to October this year, on 4 November and briefed journalists about the research at a press meeting today in London.
Dengue fever is a debilitating disease carried by biting female A.aegypti mosquitoes and causing around 25,000 human deaths a year. It mainly occurs in the tropics, but it is spreading to other climes. Paul Reiter, a medical entomology at the Pasteur Institute in Paris, told reporters that a case was reported in Holland around 4 weeks ago, and two cases have been reported in the south of France this year.
Current control methods, including bed nets and insecticides, have proved unsuccessful in controlling the disease. In addition, a vaccine has not yet been developed, and is unlikely to be available for at least 10 years, Reiter said.
Many agricultural pests are controlled through the release of sterile males. They mate with wild females and but do not produce viable offspring, and so the population size falls. If numbers drop far enough, the disease they carry can't spread.
Traditionally, males are sterilised by exposing them to radiation. But A.aegypti proved to be highly sensitive to the radiation, to the extent that they were unable to compete successfully with their wild counterparts for mates. So instead the researchers decided to tweak the mosquitoes' genes to induce sterility. And it worked. The wild females liked the GM males just as much as their fertile counterparts.
They released around 300 million sterile males over the 6 month study period, and found that the wild populations were reduced by 80% as a result – a level sufficient to effectively wipe out dengue fever in the area. "We saw a significant reduction in the target population", Luke Alphey chief scientific officer and founder of Oxitec said.
The GM males are engineered to die off in the wild, and so – Oxitec says – they do not pose a risk by persisting in the environment. The females will only mate with males of the same species, so the genetically modified trait cannot spread to other species.
Alphey said a number of other countries have expressed interest in the technology including Brazil, Panama and Malaysia, the latter of which will begin fields trials in the next few months. (SciDev.net; Malaysian government statement here.)
