Oxford-based company Oxitech genetically modified the yellow fever mosquito (Aedes aegypti) to develop the GM variety OX513A. OX513A mosquitoes are genetically modified to require the antibiotic tetracycline in order to survive to adulthood.
The mosquitoes are grown in the lab with tetracycline present, before adult males and females are separated. The male are released into the environment, where they are supposed to mate with female mosquitoes producing offspring that will mainly die off as larvae or pupae due to the lack of antibiotic in the wild. (In the lab, 3-4% survived even without the antibiotic.) This should weaken the wild population and thereby also the spread of disease potentially carried by the wild population.
The release has to be repeated regularly to keep up with the short reproduction cycle of mosquitoes. A number of problems and open questions have been identified regarding the risk of survival and establishment, gene transfer and adverse effects on ecosystems, as Ricarda Steinbrecher shows in her Scientific Opinion.
... released in Cayman Island, Malaysia and Brazil
In 2009 and 2010, Oxford-based company Oxitech released 3 million GM mosquitoes OX513A on the Cayman Islands, a British Overseas Territory. Information about these releases was only published a year later, and questions have been raised about the legality of the procedures under UK and EU legislation.
In December 2010, GM mosquitoes were released in Malaysia, and in February 2011 in Brazil. The release of 16 - 24,000 GM mosquitoes OX513A (My1) in Malaysia took place at a moment when the public was left to believe that the trials were postponed.
According to GeneWatch future releases are aledgely planned in countries like Panama, India, Singapore, Thailand, Vietnam and the USA.