Can genetically modified mosquitoes curb Dengue fever?

STEPHEN FEE: Key West is a place where people generally come to relax. And the draw's pretty obvious — white sand beaches, quaint architecture, the wildlife.

But relaxing isn't on Jessica Brown's agenda today. She's a field inspector with the Florida Keys Mosquito Control District. And since it rained yesterday, she's got her work cut out for her.

JESSICA BROWN, FLORIDA KEYS MOSQUITO DISTRICT: "Garbage cans, as long as they're turned over, they'll be good."

There are 45 species of mosquito that thrive in the often-humid Florida Keys. Brown's job — peck around peoples' backyards, clear out standing water, and use tiny pellets and even larvae-gobbling fish to kill mosquitoes before they turn into adults.

JESSICA BROWN, FLORIDA KEYS MOSQUITO DISTRICT: "So mosquitoes could — depending on how long the water sits — lay their eggs and have a really big problem."

STEPHEN FEE: Her work's part of a $10 million dollar a year effort by the Keys Mosquito Control District — which covers all of Monroe County in southern Florida — to kill off as many of the flying bloodsuckers as possible. Because they're not just a nuisance.

LOCAL NEWS ANCHOR: "Health officials find 39 cases of dengue fever in the Keys."

In 2009, an outbreak of a mosquito-borne disease called dengue fever struck the Florida Keys, the first local resurgence of the virus since the 1940s.

AILEEN CHANG, UNIVERSITY OF MIAMI HEALTH SYSTEM: "Dengue's really nasty when you get it. You know, you get a high fever. You get a rash all over. Bone pain. They call it break bone fever because it hurts so bad."

STEPHEN FEE: There were a few dozen cases and no fatalities, but the outbreak prompted mosquito control officials in the Keys to consider an experiment that's never been tried in the US before — releasing potentially millions of genetically-modified mosquitoes to kill the species that carries dengue and other dangerous diseases.

STEPHEN FEE: "But the the idea of genetically modified bugs flying around this traditionally fiercely independent community has many residents in the Keys up in arms."

LOCAL RESIDENT: "We are humans and we don't like being treated like guinea pigs."

STEPHEN FEE: Public meetings here in the Keys have exposed a deep divide between mosquito control officials and some residents who worry that the genetically modified — or GM — mosquitoes could somehow make them sick.

LOCAL RESIDENT: "I am being told what to do. And I am being at risk for a mosquito biting me."

STEPHEN FEE: "Is there any risk to my health if I get stung by a mosquito with a genetic modification like this?"

MICHAEL DOYLE, FLORIDA KEYS MOSQUITO CONTROL DISTRICT: "There's no evidence of any risk at all at this point."

STEPHEN FEE: "But no evidence of risk is different from the presence of risk, right?"


STEPHEN FEE: Michael Doyle is executive director of the Keys Mosquito Control District and says the risk of dengue fever far outweighs any risks from genetically modified mosquitoes.

MICHAEL DOYLE, FLORIDA KEYS MOSQUITO CONTROL DISTRICT: "The last thing we want people to do is to be concerned about coming down here and getting something. And so we're doing everything we can to make sure that never happens."

STEPHEN FEE: The mosquitoes that carry dengue fever — called aedes aegypti — are tough to kill. They're immune to many insecticides and breed in sometimes hard to reach places, like underneath houses or in the leaves of plants like bromeliads.

So instead of sprays or pellets that don't reach those places, officials in the Keys turned to a UK firm called Oxitec — their scientists have developed a method to alter the mosquitoes' genetic code to kill them off. Or at least kill lots of them.

DERRIC NIMMO, OXITEC: "We've inserted two genes into this mosquito. One gene is a self limiting gene and the other gene is a marker. Now the marker can identify where these genes are inserted and the other one is the one that causes the offspring to die."

STEPHEN FEE: Scientist Derric Nimmo oversees Oxitec's proposed Keys trial. He and his colleagues are able to tinker with the genes of male mosquitoes.

DERRIC NIMMO, OXITEC: "Those males have one job. They go and find a female. And they pass on their genes. And they pass on the Oxitec gene along with their own genes. Now the offspring that inherit those genes, they die. And if you release enough of the Oxitec males over a long enough period of time, you can get a crash of the mosquito population."

STEPHEN FEE: Oxitec says their method is both effective and safe. They've conducted small studies in the Cayman Islands, Brazil, and Panama — places where dengue is endemic — and were able to reduce the population of mosquitoes that can carry dengue.

And they say those experiments didn't harm anyone.

With that in mind, the five elected mosquito control officials in the Keys decided to pursue their own GM mosquito experiment in the small island neighborhood of Key Haven. And Oxitec agreed to conduct the trial for free — a trial that has yet to begin.

Initially, Florida Keys businessperson Mila de Mier says that all sounded great to her.

MILA DE MIER: "I say, 'Wow! This is fantastic. This is a really, really great idea. Be able to fight mosquitoes with another mosquitoes. What a great concept.' And obviously I don't like mosquitoes biting my kids or my dogs."

But de Mier says the more she considered it, she felt the science was too new, and not enough was known for her to feel comfortable with GM mosquitoes in her community, despite Oxitec's safety assurances.

De Mier started an online petition against the mosquito trial that's gathered 150 thousand signatures from around the world.

MILA DE MIER: "I do not want my kids to be laboratory rats. I don't want my kids to be guinea pigs. Why? Because this is a brand new technology. You get these mosquitoes, you release once and for all and then let's experiment to see what happens."

University of Florida professor Phil Lounibos has studied mosquitoes and the diseases they carry for over forty years. He's not involved with the proposed GM experiment in the Keys.

PHIL LOUNIBOS, UNIVERSITY OF FLORIDA: "We believe, those of us who have worked with mosquitoes, that the probability of something going wrong is not very high."

STEPHEN FEE: Lounibos is convinced the trial would be safe — but he questions its effectiveness. He says other mosquito species can carry dengue, and the local bugs could evolve to outsmart the genetically modified males.

PHIL LOUNIBOS, UNIVERSITY OF FLORIDA: "In the absence of dengue, the absence of a really significant threat of dengue, I see the Oxitec implementation in the Keys in the context of strong public opposition to be inappropriate."

STEPHEN FEE: Globally, dengue has surged 30-fold in the past 50 years, and increased travel from endemic areas along with warmer temperatures means the threat is spreading.

I asked de Mier what might happen if she blocks the trial and there's another, more serious dengue outbreak in the Keys.

STEPHEN FEE: "Do you worry that someone would call you up and say, 'Mila, you stood in the way. You did this.' Do you — do you worry about that?"



MILA DE MIER: "No because to be honest with you, I think the — that people have to agree. And at this point again, we are free of dengue for five years. We are, I think, as a citizen, as a mother and a taxpayer, I think these are my rights and the whole community right to choose. Do we want to be part of these tests or no?"

STEPHEN FEE: "Did you ever think maybe we should just go out and get everybody in Key Haven to just sign a piece of paper that says, I'm okay with this?

MICHAEL DOYLE, FLORIDA KEYS MOSQUITO CONTROL DISTRICT: "Every person? No. Because there's no way you can get 100 percent of people to agree to anything — that's you know putting in a road, putting a bridge, you've got someone who's going to disagree with it."

STEPHEN FEE: The FDA's Center for Veterinary Medicine — which approves any genetic modifications to animals — will have the final say over whether or not the Oxitec mosquito trial in the Florida Keys proceeds. An FDA spokesperson told us there's no timeline for when that might happen.