About a year ago, genetically modified (GM) mosquitoes were released into the wild—and they have been flying under the world's radar screen until last week. On 11 November, British company Oxitec announced that it carried out the world's first small outdoor trial with transgenic Aedes aegypti mosquitoes in the Caribbean island of Grand Cayman in the fall of 2009, followed by a larger study there last summer.
The trials were designed to test whether such designer mosquitoes could be successfully used to fight wild mosquitoes that transmit diseases like dengue fever. The announcement, made at a press briefing in London, has taken aback opponents of GM mosquitoes and surprised many researchers in the field of genetic control of insect vectors.
Some are questioning why the company stayed mum for so long, calling it a strategic mistake that provides critics of genetic modification with fresh ammunition. "I don't think they did themselves a favor," says Bart Knols, a medical entomologist at the University of Amsterdam. "This could well trigger a backlash."
Luke Alphey, chief scientific officer of Oxitec, says he "completely rejects" the notion that there was anything secretive about the trial, which was well-known within the island's population of 50,000, he says, "but just not picked up internationally."
Scientists have long debated how and when to carry out the first test release of transgenic mosquitoes designed to fight human disease—a landmark study they imagined might trigger fierce resistance from opponents of genetic engineering. A stream of papers and reports has argued that a release of any genetically modified mosquito should be preceded by years of careful groundwork, including an exhaustive public debate to win the hearts and minds of the local population. But little of that has been done in the trial in the Cayman Islands, Alphey says because the government didn't deem it necessary.
But that lack of a public debate doesn't sit well with the collaborators in a big international project, in which Oxitec is a key member, to develop and test GM mosquitoes. The program, funded by a $19.7 million grant from the Bill & Melinda Gates Foundation and led by Anthony James of the University of California, Irvine, has spent years preparing a study site in the Mexican state of Chiapas for cage studies and a possible future release of another strain of Oxitec mosquitoes. The work includes extensive dialogues with citizen groups, regulators, academics and farmers. The project, one of Gates's Grand Challenges in Global Health, would "never" release GM mosquitoes the way Oxitec has now done in Grand Cayman, says James.
Oxitec has received $5 million from the Gates program, but the Grand Cayman trial is not part of that. "As a private company, they can push their own agenda," says James, even though this could possibly hurt the field as a whole. "It's a difficult situation," he says.
Oxitec's key idea, pioneered by Alphey while at the University of Oxford in the 1990s, is to release massive numbers of lab-bred male mosquitoes equipped with a gene that kills any offspring in the larval or pupal stage. When the males mate with females of a natural population, there are no progeny—and if the transgenic males mate more often than the natural ones, the mosquito population will dwindle or even collapse.
The first small field study, designed to test whether the males can compete with their natural counterparts, was done on Grand Cayman in November and December of 2009, Alphey says. A larger study, between May and October of this year, tested the insects' population-suppressing powers. In that study, the size of the population at the 16-hectare test site dropped by 80%—a "complete success," Alphey said at a meeting of the American Society of Tropical Medicine and Hygiene in Atlanta on 4 November.
Alphey emphasizes that in designing the trial, Oxitec has worked with the Mosquito Research and Control Unit (MRCU) of the Cayman Islands, a British overseas territory. The trial abided by the rules of the territory's new biosafety bill that has yet to become law, Alphey says. Although there were no town hall meetings or public debates, MRCU sent information about the study to local newspapers. MRCU also posted a promotional video about the project on YouTube, but the clip does not mention that the mosquitoes are transgenic. MRCU could not be reached for comment.
The World Health Organization (WHO) is drafting guidelines for the release of transgenic mosquitoes, a process that will take at least 3 more months, says Yeya Touré, manager of innovative vector control interventions at WHO. Touré says he knew of the trial in Grand Cayman, and that he is not aware of any wrongdoing by Oxitec.
Medical entomologist Willem Takken of Wageningen University in the Netherlands points out that while transgenic, Oxitec's mosquitoes are programmed not to have offspring, which makes it extremely unlikely that any newly introduced genes would spread—one of the major concerns of GM opponents. But environmental groups are lamenting what they see as a lack of openness. "If these mosquitoes are completely safe, then why the hush-hush?" says Gurmit Singh, chair of the Centre for Environment, Technology and Development in Malaysia, where Oxitec hopes to start a field trial soon as well.