A genetically modified mosquito carrying an artificial fragment of DNA designed to curb the insect’s fertility has been released for the first time in south-east Asia as part of an ambitious attempt to combat deadly dengue fever that affects up to 100 M people worldwide. The GM mosquito has been developed by scientists at Oxford biotechnology company Oxitec to pass on a gene that kills the insect at the larval stage of its lifecycle. Officials in Malaysia said that the field experiment involved the release of about 6000 male GM mosquitoes into an area of uninhabited forest to monitor their dispersal. If successful, scientists hope to conduct bigger trials to test the idea that the GM males will mate with wild female mosquitoes that will produce unviable larvae that die before adulthood. On a big enough scale this should significantly reduce mosquito numbers and limit the spread of the dengue virus, which is transmitted in the bite of females. IN 2010 Oxitec carried out a much larger field trial in the Cayman Islands involving the release of about 3 M GM male mosquitoes. The company said that the local population of the Aedes aegypti mosquito, the species that carries the Dengue virus, fell by 80%. The self-destruct nature of the gene passed on by the GM male mosquitoes when they mate with wild females ensures that the genetic modification is not passed on to other organisms in the wild, said Hayden Parry, chief executive of Oxitec, which developed the GM mosquito.