Florida Keys Weigh Options For Battling Mosquitoes And Zika

Apr 22, 2016
Originally published on April 25, 2016 11:27 am

Billy Ryan visits Roy's Trailer Park on Florida's Stock Island every two months. It's part of his regular rounds as an inspector for the Florida Keys Mosquito Control District.

"Hey, I'm just checking on the yards for the mosquito control," he tells one resident, Marie Baptiste, as he heads into her yard. "OK?" No problem, she tells him.

People who live in the Keys are used to seeing mosquito control inspectors. Since an outbreak of dengue fever in 2009, the inspectors have conducted routine house-to-house checks in areas where the Aedes aegypti mosquito breeds.

And their eradication campaign — part education, part enforcement — has been effective. The last reported case of mosquito-borne dengue fever in the area was six years ago.

That same species of mosquito can carry the Zika virus. And although there have been no locally transmitted cases of the virus reported in Florida yet, and no signs that it's in local mosquitoes, state and local officials are more determined than ever to do what they can to protect residents from disease-carrying insects.

Ryan's eradication tools are pretty simple. He's got a turkey baster, a dipper — which is a stick with a cup at the end — and a plastic jar to collect samples. He also has pellets of larvicide to treat areas where mosquitoes breed.

In the narrow side yard next to Baptiste's trailer, Ryan finds a plastic barrel with a couple of inches of water at the bottom, and he spots some mosquito larvae bouncing around. Bingo. A. aegypti's favorite breeding ground.

Ryan takes a sample and shows the larvae to Baptiste, as he tips over the bucket.

"I'm going to just flip this over, OK?" he says. "If you ever see anything holding water — or any little buckets or anything — please turn them over, because we don't want to get Zika, or chikungunya or dengue fever. OK?" Baptiste agrees.

This level of attention has been effective in the Keys, thanks largely to cooperation from residents. But another approach that local and state officials are considering to get rid of mosquitoes hasn't been as popular.

The British company Oxitec wants to hold its first U.S. trial of genetically modified mosquitoes in Key Haven, not far from the trailer park.

The plan is to release about 3 million male mosquitoes that have been engineered to produce offspring that die young and can't reproduce. According to Oxitec, experiments with this approach in other countries have reduced the population of A. aegypti mosquitoes in the test areas by as much as 80 or 90 percent.

The U.S. Food and Drug Administration's center for veterinary medicine issued a preliminary assessment in March that called the likelihood of any harm to humans, animals or the environment of the proposed Oxitec experiment in Florida negligible or low. (Members of the public have until May 13 to file formal comments on the FDA's preliminary finding.)

Oxitec releases almost exclusively male mosquitoes — and only female mosquitoes bite humans, so only female mosquitoes can transmit dengue, chikungunya or Zika viruses. But Derric Nimmo, chief of mosquito research at Oxitec, acknowledges that the sorting process isn't perfect. About one in 10,000 of the released insects, he says, will be female. Still, he says, that shouldn't worry anyone.

"We looked at the females and we found there was no difference between being bitten by one of our females to being bitten by a normal female," Nimmo says. "Those female [mosquitoes] are still sterile, so their offspring inherit the gene and they will not survive."

Nonetheless, at a public meeting of the mosquito control board this week, residents of the Keys had lots of questions and concerns. Assurances from Oxitec were not enough to persuade resident Michael Kane, for example, that the test is safe.

"Nature always adapts," Kane says. "No matter how much you think you tweaked it, something else is going to happen. There's going to be unintended consequences."

After all the questions and comments, the board decided to allow residents of Key Haven to weigh in further, via a vote in August on whether to go forward with the Oxitec field test. Though the vote will be nonbinding, three of five board members have said they will abide by the results — at least in regards to Key Haven.

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KELLY MCEVERS, HOST:

The Zika virus has not yet shown up in the Florida Keys, but the islands are on high alert against the particular mosquito that carries the disease. The area continually conducts an all-out war against mosquitoes. Right now, there's a proposed trial to use genetically modified mosquitoes in that war, and residents have a lot of concerns about it. From member station WLRN, Nancy Klingener reports.

NANCY KLINGENER, BYLINE: Billy Ryan visits Roy's Trailer Park on Stock Island every two months. It's part of his regular rounds as an inspector for the Florida Keys Mosquito Control District.

BILLY RYAN: Hey, I'm just checking on the yards for the mosquito control.

MARIE BAPTISTE: OK.

RYAN: OK? All right.

KLINGENER: People who live in the Keys, like Marie Baptiste, are used to seeing mosquito control inspectors in their yards. Since an outbreak of dengue fever in 2009, they've conducted house to house inspections in areas where the Aedes aegypti mosquito breeds. In the narrow side yard next to Baptiste's trailer, Ryan finds a plastic barrel with a couple of inches of water at the bottom. And he spots some mosquito larvae bouncing around, so he takes a sample.

RYAN: Here it is. This is a ideal breeding grounds for Aedes aegyptis.

KLINGENER: The mosquito inspector's tools are pretty simple. He's got a turkey baster, a dipper, which is a stick with a cup at end, and a plastic jar to collect samples. Ryan also has pellets of larvicide to treat areas where the mosquitoes breed. Ryan shows Baptiste what he found.

RYAN: You see the water?

BAPTISTE: Mm-hmm.

RYAN: You see the larva?

BAPTISTE: Mm-hmm.

RYAN: So I'm going to just flip this over, OK?

BAPTISTE: OK.

RYAN: If you ever see anything, like, holding water like this or any little buckets or anything, please turn them over because we don't want to get Zika or chikungunya or dengue fever, OK?

KLINGENER: This level of attention has been effective in the Keys. The last reported case of dengue was six years ago, but the Keys are considering a new, cutting-edge approach. The British company Oxitec wants to hold its first U.S. trial of genetically modified mosquitoes in Key Haven, not far from here.

The plan is to release about 3 million mosquitoes. According to Oxitec, in trials in other countries, that's reduced the population of Aedes aegypti by up to 90 percent. The U.S. Food and Drug Administration has tentatively said the tests should be safe. Oxitec's mosquitoes are bred with a gene that causes the offspring to die. The company releases mostly males, but Oxitec's Derek Nimmo acknowledges the sorting process isn't imperfect. About one in 10,000 of the released mosquitoes will be female. Only females bite.

DEREK NIMMO: Those females are still sterile, so their offspring inherit the gene and they will not survive. So there's no effect on survival or in the environment.

KLINGENER: At a mosquito control board meeting in the Keys this week, residents had lots of questions and concerns. Assurances from Oxitec were not enough to persuade resident Michael Kane that the test is safe. He's worried.

MICHAEL KANE: If they release the female mosquitoes and they live and they breed, those females are going to be biting us because they are going to adapt. All you're doing is making a super mosquito - genetically modified super mosquito. Nature always adapts. No matter how much you think you tweaked it, something else is going to happen. There's going to be unintended consequences.

KLINGENER: After all the questions, the mosquito control board decide this week to allow residents in Key Haven to vote in August whether to go forward with the Oxitec trial. For NPR News, I'm Nancy Klingener in Key West, Fla. Transcript provided by NPR, Copyright NPR.