The FDA is considering whether to approve the experimental use of genetically modified mosquitoes in the Florida Keys to help stop the spread of dengue fever and other diseases. Mosquito control officials in the region say they hope to get approval to begin releasing the insects in the Keys as soon as this spring.
There are few places in the United States where mosquito control is as critical as the Florida Keys. In this southernmost county of the continental U.S., mosquitoes are a year-round public health problem and controlling them is a top priority.
Michael Doyle, an entomologist who oversees the Mosquito Control District in the Keys, is worried about one species in particular: Aedes aegypti.
“They love people,” Doyle says. He puts his hand near a fine-meshed cage full of the insects, in one of the district labs, to demonstrate his point. The mosquitoes immediately respond, clustering at Doyle’s side of the cage. They’ve clearly noticed him, and they’re interested.
“I’m not going to touch them,” he says, “because these are wild types and they could be carrying something. But if you put your hand up, they’ll fly over and land on the screen to try to bite you through the screen.”
These are the mosquitoes that carry dengue fever and chikungunya, another tropical disease that’s swept through the Caribbean and is now showing up in Florida.
After years of spraying, local health officials say, A. aegypti mosquitoes in the Keys have developed a resistance to most chemical pesticides. Now, the Mosquito Control District wants to become the first in the U.S. to try something new: genetically modified mosquitoes. The strain of insects was developed more than a decade ago by a British company, Oxitec.
Experiments already conducted in Malaysia, Brazil and the Cayman Islands have found that releasing bioengineered male mosquitoes can reduce the A. Aegypti population by 90 percent. For the past five years, officials in the Keys have been working with Oxitec to get approval from the U.S. Food and Drug Administration for similar experimental trials in Florida.
Derric Nimmo, Oxitec’s head of mosquito research, says only male A. aegypti are released in these experiments. “It mates with the females in the wild,” he explains, “and passes on that gene to all the offspring. The female goes off and lays her eggs. The eggs hatch. But then they die before reaching adulthood.”
The district says surveys it has commissioned of area residents suggest that 60 percent are OK with the trials, and 10 to 20 percent are opposed. In public meetings, though, opposition to the bioengineered mosquitoes has been strong. Some residents question whether dengue is enough of a problem in the Keys to warrant such an experiment.
“It makes no sense to me,” Deb Curley, a resident of Cudjoe Key, said at a recent public meeting. “We don’t want to be guinea pigs.”
In 2009 and 2010, Key West was hit with an outbreak of dengue fever, the first in 75 years. There haven’t been any cases since. But Doyle compares the situation to a smoldering fire. “We’ve got 2.5 to 3 million people that visit the Keys every year,” he says. “We’re very popular. So the likelihood of it arriving at any given time is good.”
Other residents say they’re concerned by how a bioengineered mosquito may affect them and the environment. Patty Crimmins, a resident of Key West, says her concerns go beyond mosquitoes. “We’re not particularly thrilled with genetically modified anything,” she says.
Oxitec’s Nimmo says that since A. Aegypti mosquitoes are nonnative, removing them would actually be an environmental plus. He says the bioengineered mosquitoes don’t live long after they’re released. “And then,” he says, “the offspring will die. We’ve shown that after trials where we stop releasing, [this strain of mosquito] doesn’t last very long in the environment. So, we’ve got a very self-limiting, safe, species-specific technology.”