11 Nov 2010

GM mosquito battles dengue fever

British scientists say they have found a way to cut down on cases of the potentially fatal disease dengue fever, by releasing genetically modified mosquitoes into the wild.

British scientists say the first field trial of a genetically-modified (GM) mosquito has cut numbers of wild mosquitoes capable of carrying the potentially fatal disease.

Scientists at the Oxford based biotech company Oxitec inserted a gene into male mosquitoes that is fatal to any of its offspring.

Three million of these insects were then released into the wild so they could mate with female mosquitoes. Although the females still laid eggs, which hatched into mosquito larvae – all of these larvae then died before reaching adulthood.

Oxitec said a recent six-month long trial at a village on the Cayman Islands in the Caribbean had proven successful.

Population numbers of Aedes aegypti – the mosquito that carries dengue fever – were reduced by 80 per cent.

In the absence of drugs and vaccines, the way to control this disease is to control the mosquito, and that’s what this technology will do. Dr Luke Alphey, Chief Scientific Officer of Oxitec.

Dr Luke Alphey, the Chief Scientific Officer of Oxitec, told Channel 4 News the technology is completely safe.

“The males don’t bite – so what we’re releasing doesn’t bite. All they are interesting in is finding and mating the wild females, which is what we want them to do,” he said.

Scientists have genetically modified a mosquito in a bid to tackle dengue fever

Dengue fears

Dengue fever is on the rise globally. The World Health Organisation (WHO) estimates that 2.5bn people – two fifths of the world’s population – are now at risk from the virus. WHO believes there are more than 50 million cases of dengue each year throughout the tropics.

Infections can be mild, but many result in a serious flu-like illness. In some cases the virus causes dengue haemorrhagic fever, a complication so serious it is often fatal.

“In the absence of drugs and vaccines, the way to control this disease is to control the mosquito, and that’s what this technology will do,” said Dr Alphey.

Unlike the outcry over GM crops there has been little public opposition to the development of bioengineered mosquitoes. However, some campaigners caution that even if the technology is perfectly safe, it could have unpredictable ecological impacts.

Pete Riley from the campaign group GM Freeze told Channel 4 News more research was needed first on food chains in tropical areas, and is concerned about what would happen to other wildlife if mosquitoes were made less abundant.

“They can’t ignore these questions,” he said. “If there are going to be changes to the local eco-system, they need to find out.

“If you take mosquitoes out of the system, which is the intention of Oxitec – then what affect will that have on the rest of the food chain? Other predictors and predictor pray relationships could be significant and surprising.”

Insect’s environment

Scientists at Oxitec argue that Aedes aegyptii has spread worldwide because of humans so the insects’ ecology is essentially artificial.

“All through the Americas and southeast Asia where dengue is well known and a major problem, it’s not even a native species,” said Alphey.

If you take mosquitoes out of the system, then what affect will that have on the rest of the food chain? Pete Riley, Campaign Director, GM Freeze

Because the mosquito does away with the need for insecticides it is better for the environment, he adds.

“From the point of view of human health and the environmental safety – then it is an extremely safe and extremely targeted technology.”

Pleased with the results of the trial in the Cayman Islands, Oxitec’s chief executive Hadyn Parry is confident other governments will want to test their technology.

“Now what we need to do is roll this out and do demonstration trials in different environments in different countries around the world,” he said.

The Malaysian government has authorised a trial beginning later this month. The company expects to conduct trials in Brazil, Panama and the USA next year.