So, Oxitec's genetically modified mosquitoes are an ostensibly elegant solution to Doyle's conundrum. "I've looked at all other options for Aedes aegypti control, but they're too expensive or environmentally damaging. This sounds like the best option we have going."
Over in Oxitec's mosquito factory on the outskirts of Oxford, England, scientists use razor-sharp glass needles to inject small amounts of DNA into tens of thousands of mosquito eggs. Most of the eggs will die, but the ones that survive will incorporate the extra DNA into their genome and go on to develop two genetic modifications that can be passed down. The first causes the mosquitoes to glow fluorescent red when placed under a high-powered microscope. Though this may sound like something from a Michael Crichton novel, it's a relatively old trick that's used to track all types of research animals. The second modification, the insertion of an autocidal gene, is what causes the mosquitoes to self-destruct.
Chris Sweeney
Michael Doyle, executive director of Florida Keys Mosquito Control, in front of one of the four helicopters used to wage aerial assaults on mosquitoes.
Courtesy of Oxitec
Aedes aegypti mosquitoes are the only species in the South Florida capable of spreading dengue fever.
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In the lab, the modified mosquitoes are fed tetracycline. This common antibiotic essentially turns the death gene off. This allows the insects to stay alive, breed, and produce eggs that now contain the gene.
"All the fancy genetic stuff is done over [in England]," Doyle explains. "I call Oxitec, they send a boxful of eggs, we grow the eggs in cake pans, give them food and water, and sort them in a lab we'll set up in a trailer."
By sorting, Doyle means weeding out any females by looking at the size of the larvae — males are smaller than females. It's the most crucial step in the process because only female mosquitoes bite humans, and releasing hordes of modified mosquitoes capable of sucking our blood would be counterproductive at best. Doyle acknowledges, however, that this sorting method isn't foolproof; about one female gets through and is released for every 1,500 male mosquitoes, he says.
"The chance of getting bit by a female genetically modified mosquito is pretty small, but it's not impossible. It's going to happen." The effects of such a bite are unclear, but the idea of getting bitten by a mutant mosquito could freak people out. Environmental groups and organizations opposed to genetic modifications of any sort have been vocal over the lack of information on this aspect. Oxitec maintains that the proteins composing the genetic modification aren't present in mosquito saliva and thus won't be transmitted during a bite. It's a sentiment that scientists who are critical of the company tend to agree with.
Doyle and his team are now busy looking for two similar six-block-by-six-block areas in Key West where they can conduct their experiment. In phase one, they intend to release a few thousand Oxitec mosquitoes and set traps. From the mosquitoes that get caught, they can determine the ratio of Oxitec mosquitoes to normal ones. Then, they'll do a second phase, releasing ten Oxitec mosquitoes for every wild one. Doyle says that over six months, 2 million to 6 million genetically modified mosquitoes will be released. Saturating the test site with the modified mosquitoes should increase their odds for successfully mating with normal females.
A potential pitfall is that the street-smart, wild males will simply outgun the lab-pampered mosquitoes. But if all goes as planned and Oxitec mosquitoes get to the females first, the offspring will hatch and live for a few days before the genetic modification kicks into effect and shuts down the cellular machinery needed for the pupae to become functioning adults. Hordes of tiny mosquito corpses will flow through the shallow breeding grounds.
Doyle is well-aware of the experimental nature of a release and says he needs to be a "cautious buyer." At the same time, he's eager to get the test under way because the threat of dengue looms as millions of tourists flock to the Keys each year.
When Joel Biddle, Mila de Mier, and their Conch friends began looking into Oxitec's history, they found a few worrisome things about the decade-old, privately funded company. Oxitec, which employs about 40 people, has consistently come under fire from environmental organizations, anti-GM groups, and academics for its lack of transparency when carrying out experiments. So far, the company has released mosquitoes in Brazil in 2011, Malaysia in 2010, and the Cayman Islands — where more than 3 million genetically modified mosquitoes have been dispatched since 2008.
Few peer-reviewed scientific journal articles have been published demonstrating the effectiveness and safety of genetically modified mosquitoes when released in the wild. Those that have been published include an Oxitec staffer among the authors, and there are no independent, third-party studies under way.
Opponents, including the Conchs at the real estate office, hone in on the Cayman experiment because it's the furthest along. About four years ago, Oxitec and the Cayman mosquito control authority collaborated on an experiment without providing much information to the scientific community or local residents about the release. In November 2010, Oxitec took the stage at a medical conference in Atlanta and delivered findings from what was the first field trial ever of genetically modified mosquitoes. Some researchers in the crowd were surprised that, all of a sudden, a British biotech company was announcing that it had released its mutant mosquitoes in the wild without consulting the larger research community.
