Florida will become home to 750 million genetically-modified mosquitoes. Local authorities have approved the release of these insects in a bid to bring down the numbers of local mosquito swarms.

Mosquitoes suck — more to the point, they suck our blood. Not only is this really annoying and itchy, it can also be dangerous: mosquitoes are carriers of diseases like dengue fever and Zika, which they spread by coming into contact with the blood in our veins.

Engineered to fail

Aedes aegypti, the most common type of mosquito and so the one most likely to be biting you in your sleep, is in fact an invasive species in Florida. They’re typically found near standing pools of water, where they lay their eggs and spend their larval days.

Because nobody has much love for them, we’ve come to rely on pesticides to keep them away or, ideally, very dead. But the insects have developed a resistance to such compounds.

In order to keep their numbers in check, Florida officials have approved the release of around 750 million genetically-modified mosquitoes into the wild. All these mosquitoes, known as OX5034, are males, and carry a special gene that will kill off any female offspring they have. Since only female mosquitoes need to bite for blood (which they use as nutrients for eggs), this would dramatically limit the threat they pose to public health.

This decision comes after the US Environmental Agency granted permission to Oxitec, a British-based company operated in the US, to produce these modified mosquitoes.

The approval of this release was not without its critics. Environmental groups warn that we don’t know enough about how such mosquitoes behave in the wild to know for sure that it’s safe to release them. Their biggest worries are the creation of hybrids between wild and modified mosquitoes, and possible damage to the ecosystems that these insects are part of. An online petition on Change.org that plans to stop the US being “a testing ground for these mutant bugs” has also gathered nearly 240,000 signatures so far.

Oxitec rebuts that the issue has been studied amply and that the release should go without a hitch. Either way, the insects are set to be released in 2021 in the Florida Keys islands.

This isn’t the first time that modified mosquitoes have been used to try and control wild populations. They were previously also used in Brazil to combat Zika, and Oxitec said the results of that experiment were “positive”. It plans to also deploy the mosquitoes in Texas beginning sometime next year — although the company hasn’t gotten state or local approval as yet, it did receive the green light on the federal level.

“We have released over a billion of our mosquitoes over the years. There is no potential for risk to the environment or humans,” an Oxitec scientist told AP news agency.