Billions of insects, all sterilized by intense bursts of radiation, have been reared in laboratories like Moscamed and released to mate in the wild.
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In , SIT , which prevents the organism from reproducing, successfully eradicated the screwworm—a parasite that attacks the flesh of warm-blooded animals—from North America. But radiation is difficult to use properly on insects as small as mosquitoes. Administer too little and they remain virile; zap them too powerfully and the insects are left so weak that they are unfit to compete for mates.
One day, Alphey, now a visiting professor of zoology at Oxford, bumped into a colleague who was talking about sterile insect technique. Alphey, who knew little about the field, began to think about how to supplant radiation with the practices of modern molecular biology. Alphey is reserved, with a mop of brown hair and pensive eyes; one can practically see his brain in motion as he works out a scientific problem. His goal was not exactly to sterilize the males but to alter their genes so that any progeny would die. If he could do that without using radiation, he reasoned, the insects should be fit to compete sexually for wild females.
Alphey faced several scientific hurdles. He would have to engineer only males. Female mosquitoes bite, so genetically modified females could, in theory, pass novel proteins to humans, with unknown consequences. It turns out that, with Aedes aegypti , females are considerably larger than the males. That was a lucky break, because it means you can easily separate them on the basis of their size.
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Once released, the males would have to live long enough to impregnate females, and they would need to be healthy enough to compete with wild males for the right to do so. In , Oxitec was spun off as a company apart from the university.
Alphey began to speak at tropical-disease meetings and in dengue-infested countries; he also gathered support from private investors and public-health philanthropies, including the Gates Foundation and the Wellcome Trust. In , the company ran a series of field trials in the Cayman Islands, releasing 3. OXA became the first engineered mosquito set free on the planet. The number of wild Aedes aegypti mosquitoes in the area fell by eighty per cent in two months. It was only a test of feasibility; no one knew how it might affect the local ecology or whether it would actually reduce the incidence of dengue.
Environmental activists feared that the release of engineered insects could set off a cascade of events that nobody would be able to control. In , Key West, Florida, suffered its first dengue outbreak in seventy-three years.
There were fewer than thirty confirmed cases—a trifling number compared with the millions who are infected each year in South America, Africa, and Asia. There are just twenty thousand full-time residents in Key West, but, with more than two million visitors each year, the town is highly dependent on tourists. I was there during spring break, which is not the best time to visit unless you have a particular interest in keggers, tequila, or Eagles cover bands.
Even a small dengue outbreak in Key West would send a troubling message. In , there were twice as many cases. Doyle told me. We are an ideal host. Doyle is a soft-spoken man with rimless eyeglasses and a neatly trimmed mustache. He pointed out that, when it comes to contracting dengue, the way people live is as important as where they live: from to , Texas reported sixty-four cases of dengue along the Rio Grande, whereas there were more than sixty thousand cases in the Mexican states just across the river.
But Texans have screens on their windows and keep the windows closed , drive air-conditioned cars, and spend little time outdoors. The data looked solid, and certainly we need to think differently about mosquito control than we have in the past. It would be the first in a series of hearings intended to explore the possibility of testing the mosquitoes in one relatively isolated Key West neighborhood. Because they are living in a sea of dengue. Opponents mobilized within hours of receiving notice of the meeting.
She was dressed in the peaches and pinks one associates with southern Florida. She was also wearing combat boots. Her children and grandchildren are conchs, too. We have had no dengue for two years and maybe, at most, we will have a few cases. Certainly not big enough to bring in an unnatural insect about which we know so little.
You are in much more danger of being hit by a car. It is impossible to predict the likelihood of a dengue outbreak based on the number of past infections. All it takes is the presence of the mosquito and the virus. Key West has plenty of the former; the rest is a matter of aggressive pest control—and chance. Once infectious mosquitoes start biting humans, an epidemic can erupt within weeks, as the virus moves from vector to host and back again.
What would happen if they bit us? Getting rid of dengue would be wonderful, of course, but what would happen if we did succeed and these mosquitoes simply vanished from the earth? Those are reasonable concerns. She is not an important pollinator of plants, like the bee. She does not even serve as an essential food item for some other animal. That the mosquito plagues human beings is really, to her, incidental. She is simply surviving and reproducing. Will other pests increase in number? Will targeted diseases be able to switch vectors?
Will these vectors be easier or more difficult to control? It would be irresponsible to deploy transgenic insects widely without adequate answers to those questions, but most have been addressed in environmental-impact statements and by independent research. If the results were put to the vote of biologists, the overwhelming response would be: the potential benefits far outweigh the risks.
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There are no birds, fish, or other insects that depend solely on Aedes aegypti. So I come at it from that perspective. I am biased against mosquitoes. And Aedes aegypti cause immense damage. Raging epidemics of dengue would affect our economy badly. Go back to the days of yellow fever in this country and it had real demographic consequences. Whole towns died. Life expectancies in certain areas were reduced.
Mark Q. Benedict agrees.
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Benedict, an entomologist at the University of Perugia, has researched genetically modified insects for years and written about them extensively.