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Experts in the safety of genetically modified (GM) organisms have expressed concern over the release of GM mosquitoes into the wild on the Cayman Islands, which was publicised internationally only last month — a year after their initial release.

The trial of the OX513A strain of the dengue-carrying Aedes aegypti mosquito, developed by UK biotechnology company Oxitec, was carried out on Grand Cayman island by the Cayman Islands' Mosquito Research and Control Unit (MRCU) in 2009, followed by a bigger release between May and October this year. Together they represent the first known release of GM mosquitoes anywhere in the world.

Unpublished results of the trials, showing that the GM male mosquitoes competed with wild males, were presented at the American Society of Tropical Medicine and Hygiene annual meeting in the United States, last week (4 November).

The male GM mosquitoes mate with normal females to produce larvae that die unless the antibiotic tetracycline is present. In tetracycline's absence an enzyme accumulates to a toxic level, killing the larvae. The developers hope the strategy could be combined with other mosquito control methods to reduce transmission in dengue-prone areas.

Ricarda Steinbrecher, a geneticist and co-director of EcoNexus — a UK-based non-profit research organisation — expressed surprise that the trials had occurred, saying that they had not been mentioned at the fifth meeting of the Parties to the Cartagena Protocol on Biosafety — which addresses international safety issues relating to GM organisms in Nagoya, Japan, last month.

She described the lack of publicity surrounding the trials as "worrying, both from the scientific perspective as well as public participation perspective".

Steinbrecher said that until a full, long-term environmental assessment of the Cayman trials has been carried out, the recently announced Malaysian trials of the same strain should not go ahead.

Just over three million male mosquitoes were released in the Cayman Islands this year. Oxitec sent the GM eggs to the islands, which are a British overseas territory, and they were hatched and grown at the MRCU.

Angela Harris, senior researcher at MRCU, told SciDev.Net that her unit consulted with several Cayman Islands' government departments beforehand.

"Currently there is a draft biosafety bill, and despite the fact that this bill has not yet been implemented we carried out a risk analysis and review of the trial as if this bill was already in place."

She said that there had been a newspaper article and public consultation within the Cayman Islands.  

Aedes aegypti mosquito by Flickr/Marco Gaiani

Aedes aegypti mosquitoes transmit dengue fever

Flickr/Marco Gaiani

Luke Alphey, research director at Oxitec, said an extensive risk analysis was carried out and "we did lots of engagement work in Cayman, but no special effort either to spread the word internationally or not to [do so]". On the sidelines of a press conference in London today he said that he had not wanted to publicise the trial until the results were known. He did not know what the Nagoya meeting was, he said. An environmental assessment of the trial site is now being carried out.

Alphey said that the experiment complied with the Cartagena Protocol because prior informed consent was obtained from the Cayman government.

John Marshall, of Imperial College London, who has argued that the Cartagena Protocol needs overhauling to deal with the special demands of GM insects, said: "Because the mosquitoes aren't going to spread to other countries, it's a national issue. I think Oxitec has done everything they needed to do."

The wild mosquito population in a 16-hectare urban area is believed to have been reduced by about 80 per cent. The next step for Oxitec, said Alphey, is to test the strategy in conjunction with other mosquito control methods.

Kathy Jo Wetter, a researcher with the ETC Group (Action Group on Erosion, Technology and Cooperation), a Canada-based organisation that promotes the socially responsible development of technologies, said ETC was unaware of the release.

"Oxitec considers its trial 'successful' just days after the experiment has ended," she said. "But unintended impacts on the environment cannot be known, and Oxitec's unproven technology could make things worse in the long term. There is no possibility of recall if something goes wrong — who takes responsibility in that case?"

"Extreme techno-fixes require extreme precaution," she added.

Alphey said they are waiting for approval for the release of GM mosquitoes in Brazil, Panama and the United States.

See below for a video of rearing and release of Oxitec's GM mosquitoes in the Cayman islands by the Mosquito Research and Control Unit (Grand Cayman):

 


Additional reporting by Mićo Tatalović

 

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