Can Genetically Modified Bugs Reduce Dengue Threat?

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An invasive species of mosquito has recently brought dengue fever, a potentially fatal illness, to the Florida Keys. Florida authorities are on the hunt for a new weapon to fight these insects — and they're looking to Britain. A company called Oxitec is developing genetically modified mosquitoes that it claims can wipe out wild populations — and with it, the threat of dengue.

MICHELE NORRIS, Host:

From NPR News, this is ALL THINGS CONSIDERED. I'm Michele Norris.

MELISSA BLOCK, Host:

And I'm Melissa Block.

Summer means a lot of happy sunny things in Florida, but for residents of the Florida Keys, it could also mean the reappearance of a deadly disease. Dengue fever has returned to the Keys for the past two summers after being absent for decades.

Dengue is spread by mosquitoes, and Florida is searching for new weapons to fight the bugs. That search has led them to a company in Britain called Oxitec. It's developing genetically modified mosquitoes.

And as Geoff Brumfiel reports, the company claims its mosquitoes can wipe out the wild kind.

GEOFF BRUMFIEL: I'm standing in the middle of Oxitec's mosquito breeding lab, which looks like a walk-in meat locker but feels like a tropical rainforest.

It's actually quite comfortable in here, yeah.

NORRIS: You think? By spending a few hours, you will change your mind, I believe.

BRUMFIEL: That's Genevieve Labbe. She works here. Now, before I go any further, let's get this out of the way. These genetically modified mosquitoes are all normal size. They're not superintelligent or anything like that. And even if one does get out of its cage, which happens occasionally, Labbe has a backup plan in hand.

NORRIS: It just looks like a tennis racquet, except the mesh is electrified.

BRUMFIEL: Does it hurt, I mean, if you ever touch it?

NORRIS: Do you want to try?

BRUMFIEL: Yeah. I'll give it a shot. Ow.

When Labbe isn't swatting mosquitoes or visitors, she's busy injecting hundreds of tiny mosquito eggs with small bits of customized genetic material. The results are these little guys. They look and act normal, but the gene Labbe gives them makes their offspring dependent on a special dietary supplement that they can only get in the lab. Without the supplement, they can't develop normally, says Labbe's boss, Luke Alphey.

D: If you're really, really nice to them, a few percent, two or 3 percent can survive.

BRUMFIEL: Out in the real world, life gets tougher.

D: We have no evidence of any survival in the field.

BRUMFIEL: With the electrified tennis racquet over there, you might wonder why they're going to all this trouble to come up with a new way to kill mosquitoes. Well, the goal isn't to kill one or two. It's to wipe out whole populations, and in doing so, control diseases they carry like dengue fever. Fifty million people catch dengue each year, and it's potentially fatal.

D: There's no drug. There's no vaccine. Bed nets don't protect you because this mosquito bites during the daytime. So there is only mosquito control.

BRUMFIEL: That's why health officials in the Florida Keys are interested. In 2009, mosquitoes carrying dengue returned to the Keys for the first time in decades. Local authorities don't have a lot of weapons. They can tip out pools of water where mosquitoes lay their eggs or spray insecticides, but in urban environments, these strategies don't work very well.

Oxitec has a new plan, and like a lot of good plans, it uses sex. The company breeds a generation of male GM mosquitoes then releases them to mate with the wild females.

D: The males will go and look for females. Oh, yeah, they're highly developed to do that. You might say that's all they're for. And, of course, chemicals will generally not do that.

BRUMFIEL: Field trials in the Cayman Islands last year appeared to show it works. Oxitec released its genetically modified males, and, Alphey says, the population dropped by a whopping 80 percent. He thinks he could do even better by spreading his killer males over a wider area, and the technology could also be applied to agricultural pests.

Now, male mosquitoes don't bite, so the GM version doesn't pose a risk to people, and they can't spread their genes, pass to generation because their offspring are designed to die. But even then, some environmentalists aren't fans of what Oxitec is doing.

One of them is Helen Wallace with the British nonprofit GeneWatch. She's been watching the company's trials in the Cayman Islands and elsewhere, and she's concerned about the mosquitoes.

D: Yes. It sounds a bit strange to be trying to save mosquitoes, doesn't it? But I think the key issue isn't really whether the species itself should be wiped out. I think we just want to be a lot more sure that it isn't going to cause unintended problems.

BRUMFIEL: Wallace worries that killing lots of mosquitoes could suddenly alter the local ecosystem or even trigger the rise of other disease- carrying animals and causing new outbreak. She also worries that the technology is moving too quickly for many countries.

D: Oxitec chose to do its first open release of these mosquitoes in the Cayman Islands, which has no biosafety law and has no environmental information law.

BRUMFIEL: Oxitec's Luke Alphey says the company followed a draft law and worked hard to inform the government and the public. Ultimately, he thinks that GM insects are safe and can work better than insecticides.

D: What we have is not a panacea or a magic bullet that will cure all the world's insect-related ills, but I think it will be a very valuable additional tool.

BRUMFIEL: Many scientists in the U.S. agree, but the tool is unlikely to be available to Florida residents this season. Just like in other countries, U.S. regulators are struggling to come up with rules and safeguards. They're now consulting with researchers and hope to develop a strategy for all GM insects soon.

For NPR News, this is Geoff Brumfiel in London.

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