The U.S. Food and Drug administration is considering a plan in which millions of genetically modified mosquitoes would be set loose in the Florida Keys as a way to combat the spread of tropical diseases.

Top image: A modified Aedes aegypti mosquito (Oxitec).

As the climate warms, tropical diseases like Dengue and Chikungunya are starting to make their way northwards to the continental United States. These two diseases in particular are spread by the Aedes aegypti mosquito, leading British biotech firm Oxitec to propose a plan in which "autocidal" GMO mosquitoes would be released in the Florida Keys. In theory, these modified mosquitoes would work to reduce the population. To date, no GMO insects have ever been released in residential areas.

As the Associated Press reports:

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[Oxitec] patented a method of breeding Aedes aegypti with fragments of proteins from the herpes simplex virus and E. coli bacteria as well as genes from coral and cabbage. This synthetic DNA has been used in thousands of experiments without harming lab animals, but it is fatal to the bugs, killing mosquito larvae before they can fly or bite.

Oxitec's lab workers manually remove modified females, aiming to release only males, which feed on nectar and don't bite for blood like females do. The modified males then mate with wild females whose offspring die, reducing the population.

Oxitec has built a breeding lab in Marathon and hopes to release its mosquitoes this spring in Key Haven, a neighborhood of 444 homes closely clustered on a relatively isolated peninsula at the north end of Key West.

According to the FDA, no field tests will be permitted until it's had time to "thoroughly [review] all the necessary information."

Amongst the many concerns (like unanticipated downstream ecological effects), some people are worried that genetically modified DNA might get into humans after being bitten. It's a fear that some outside observers say hasn't been proven one way or another, even though Oxitec claims it isn't possible. The AP spoke to Guy Reeves of Germany's Max Planck Institute, who says the biotech firm needs to show that synthetic DNA causes no harm if and when it's transferred into humans by the mutated mosquitoes.

It's also important to note that back in 2012 Oxitec unilaterally released 3.3 million GMO mosquitoes in the Caymen Islands over a period of six months. The firm says it resulted in the suppression of 96% of Aedes aegypti. Another test in Brazil likewise produced beneficial results.

Oxitec is clearly onto something, but it's fair to say that people are worried. The claim that Oxitec did not get informed consent, however, or did not conduct the necessary testing, has been leveled by critics unsatisfied with the past actions of regulatory bodies. For instance, the BBC has reported that

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we found that Oxitec's technology and methodology were reviewed and approved by independent regulatory authorities in each of the countries in which releases have taken place. We also found that in the initial Brazilian trial community members were asked to approve the project and also to allow project staff to enter their homes to survey for mosquitoes: there was 100% participation.

Given the sensitive nature of the issue, it's easy to understand why there's controversy and even confusion as to what constituted "proper" informed consent or sufficient testing. Given all concerns — even those that are unfounded — it's quite likely the FDA won't allow this. At least not yet.

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*NOTE: This article was modified on 01/27/15 to clarify the concern about the Oxitec tests and the claim that modified DNA is transmissible via bites, and to remove the claim that further human health studies are required.

There's much more to this developing story at the AP.