Hundreds of thousands of genetically modified mosquitoes are awaiting federal approval for release into the Florida Keys as part of an experiment aimed at reducing the risk of dengue fever.

Mosquito control officials have requested the Food and Drug Administration's sign off on the experiment that would be the first of its kind in the U.S.

Some residents of the tourist town of Key West worry though on how much research has been done to determine the risks of releasing genetically modified mosquitoes on the Keys' fragile ecosystem.

Let us go! An entomological technician with the Florida Keys Mosquito Control District, sorts and counts dead mosquitoes in Key West, where officials are hoping to release genetically modified mosquitoes into the wild

Officials are targeting the Aedes aegypti mosquitoes because they can spread dengue fever, a disease health officials thought had been eradicated in the U.S. until 93 cases originated in the Keys in 2009 and 2010.

The trial planned by mosquito control officials and the British company Oxitec would release non-biting male mosquitoes that have been genetically modified to pass along a birth defect that kill their progeny before reaching maturity.

The idea is that they will mate with wild females and their children will die before reproducing. After a few generations, Key West's Aedes aegypti population would die off, reducing the dengue fever risk without using pesticides and at relatively a low cost, the proponents say. There is no vaccine for dengue fever.

'The science of it, I think, looks fine. It's straight from setting up experiments and collecting data,' said Michael Doyle, pointing to research Oxitec has had published in peer-reviewed scientific journals. He inherited the project when he took the lead at the Florida Keys Mosquito Control District in mid-2011.

Genetic adaptions: An Aedes aegypti mosquito is seen feeding on a woman's arm while the ones genetically modified would be non-biting males that pass along a birth defect killing their progeny before reaching maturity

The district's website says the modified genes will disappear from the environment after the mosquitoes carrying it die, resulting in no permanent change to the wild mosquito population. The district also says that the mosquito species isn't native to the Keys, nor is it an integral food source for other animals.

Dengue fever is a viral disease that inflicts severe flu-like symptoms — the joint pain is so severe its nickname is 'breakbone fever.' It isn't fatal but victims are then susceptible at subsequent exposures to dengue hemorrhagic fever, which can be.

'It's very uncomfortable. You ache all over, you have a terrible fever,' said Joel Biddle, a Key West resident whose dengue fever symptoms lasted more than a week in 2009.

Biddle is among those concerned about the Key West trial. He worries the modified genetic material will somehow be passed to humans or the ecosystem, and he wants more research done. He and other Key West residents also chafe at the fact that the project was in the works long before it was made public late last year.

No vaccine: Influenza vaccines are seen before a worker while there is no vaccine for dengue fever which causes similar non-fatal symptoms but also makes victims susceptible to dengue hemorrhagic fever, which is

Only female mosquitoes bite, so the modified genetic material wouldn't be passed on to humans, Mosquito control and Oxitec officials said. They also say they're being transparent about their data and the trial.

Real estate agent Mila de Mier has collected more than 117,700 signatures on a petition she posted on Change.org against the trial. Most come from outside the Keys, which de Mier says shows that tourists don't support the mosquito control district.

'We are dependent here on our tourists, and people from all over the country have been sending the message,' de Mier said.

A University of Florida professor who studies mosquito control said Oxitec's technology works and evidence from the company's experiments elsewhere show it can control mosquito populations, but it's not clear whether its methods are as effective at controlling the risk of disease transmission.

Phil Lounibos of the Florida Medical Entomology Laboratory also said it would take repeated releases of modified mosquitoes for the program to work, and the public outcry against genetically modified organisms, even when it's irrational, may be insurmountable.

Growing problem: A field inspector with the Florida Keys Mosquito Control District tests a sprayer used to spray pesticides which have unfortunately become less effective on mosquitoes today

'The public resistance and the need to reach some agreement between mosquito control and the public, I see that as a very significant issue, outside of the (operating) costs, since this is not just a one-time thing,' Lounibos said.

The Aedes aegypti has shown resistance to pesticides used to control other species, and is the most difficult for the district to manage. Common in the Southeast and the Caribbean, it lurks in standing water around homes and businesses and can breed in containers as small as bottle caps.

District inspectors go door-to-door to remove the standing water where they breed, a time-consuming task. The district spends roughly $1 million a year to suppress Aedes aegypti, 10 to 15 percent of the agency's budget, Doyle said.

'Unfortunately, control of Aedes aegypti is a never-ending job,' said Larry Hriber, the mosquito control district's research director.

In the trial, thousands of male mosquitoes bred by Oxitec would be released in a handful of Key West blocks where the Aedes aegypti is known to breed; the number of mosquitoes in those neighborhoods would be measured against the numbers from similar blocks where no modified mosquitoes were released.

Exhausting count: Key West's district spends roughly $1 million a year to suppress Aedes aegypti mosquitoes, what they say is 10 to 15 percent of the agency's budget

The state's agriculture department oversees the mosquito control district, and Doyle said he would not expect any challenge from the state if the FDA signed off on the trial.

The mosquito control district wouldn't need any local permit for the trial, either, but officials held a public meeting earlier this year and have posted information on the agency's website.

Still, it could take years for the FDA to approve the trial.

There hasn't been a case of dengue fever in Key West since November 2010, but two other cases were reported elsewhere in South Florida this fall.

The mosquito trial proposed for Key West wouldn't be the first release of genetically modified insects in the U.S.