There’s a battle brewing in the Florida Keys. It involves blood suckers that are spreading disease. The fight to take them out is going down in a science lab.

Scientists are a few months into an experiment to stop the invasive Aedes aegypti mosquito. Their weapon of choice? A genetically modified mosquito.

But some environment advocates question the strategy.

This year, the Florida Keys had an outbreak of Dengue fever. It gives new urgency to the controversial effort to get rid of the Aedes aegypti, which has become harder to fight. 

Chad Huff with the Florida Keys Mosquito Control District says the mosquito is resilient. 

“The Aedes aegypti is a very hearty mosquito that thrives exclusively around people,” Huff explained.

The species is from a small part of Africa, but it somehow spread all over the world, including in Florida. The mosquito carries diseases such as Dengue fever, Zika and yellow fever. 

The Florida Keys Mosquito Control District has had a long, on-going fight with the mosquito. So far, nothing really seems to stick.  

"Insect pests are becoming resistant to the traditional tools that have been used to control them," said Meredith Fensom, the head of Global Public Affairs with Oxitec. 

The first line of attack: larvicide. If that fails, plan B? Adulticide. But what happens when this also stops working?

Oxitec was called in to help the mosquito control district to stop the spread of the insects. The company’s approach? Fight mosquitoes with mosquitoes. The mosquito used in the fight is genetically engineered.

"For our mosquito project, Oxitec will release our non-biting male mosquitos. No male mosquitos bite. You've never been bitten by a male mosquito," Fensom explained.

This how the mosquitoes are genetically engineered:

A self-limiting gene is first inserted in certain eggs that later morph a new mosquito strain. 

Only male mosquitos from this strain are released. 

When the GMO mosquitoes mate with the invasive female mosquitos, they pass the self-limiting gene along. The female offspring from these encounters cannot survive.

"You have a rapid, very drastic reduction in the wild mosquito population that way,” Fensom said. “In some of our recent projects in Brazil, we were able to reduce about 95% of the wild Aedes aegypti mosquito population in just about 12 weeks.”

Millions of the male mosquitos will be released. The exact location is still being determined.

"When we start, it we will have our male mosquito eggs in little boxes, and we just add water to the boxes, and in about a weeks’ time, these mosquitos release themselves,” Fensom explained. 

Oxitec says the GMO mosquitoes decide when they are going to come out of the box and these boxes are refilled or replaced about every week.

Mosquito control officials said the Environmental Protection Agency and other government agencies approve the program.  

"A lot of people have looked at this in a lot of different ways and they've decided, yeah, go ahead, let’s see if it works like it's supposed to,” Huff explained.

Meanwhile, some worry about the effects this project will have on the environment. 

More than 235,000 people have signed a Change.org petition to stop the plan. And several advocacy groups, such as the Center for Food Safety, want to ax it and criticize the EPA for approving the plan. 

The group released a statement in response to the project: 

“Neither EPA, FKMCD, nor Oxitec is aware of how this unprecedented release of millions of GE mosquitoes will affect Monroe County or the State of Florida because EPA refused to carry out an environmental impact statement. To proceed with this Jurassic Park-like experiment before EPA performs its most basic environmental review to determine what the negative impacts that these GE mosquitoes may have on public health, endangered and threatened species, and the environment in the Florida Keys is unlawful and downright irresponsible.”

Oxitec scientists say their strategy will not hurt the environment.  

"One of the big advantages of this technology is how environmentally friendly it is. We're not putting harmful chemicals into the environment,” Fensom said. “We are targeting an invasive, disease spreading mosquito, and beneficial insects like bees and butterflies are unharmed."

The EPA released this statement to NBC 6:

"Before granting the experimental use permit to field test the use of genetically engineered Aedes aegypti mosquitoes as a way to reduce mosquito populations to protect public health from mosquito-borne illnesses,  EPA conducted an extensive risk assessment based on the best available science and considered public input. EPA does not expect the trial to have adverse effects to animals in the environment. Oxitec is required to monitor and sample the mosquito population weekly in the treatment areas to determine how well the product works for mosquito control and to confirm that the modified genetic traits disappear from the male Aedes aegypti mosquito population over time. EPA has also maintained the right to cancel the EUP at any point during the 24-month period if unforeseen outcomes occur. The courts have consistently held that Congress did not intend for NEPA’s requirements (either an Environmental Assessment or an Environmental Impact Statement) to apply to EPA registering pesticides under the Federal Insecticide, Fungicide, and Rodenticide Act."

Mosquito control officials say the program will take place early next year before mosquito season starts.