Florida releasing genetically modified mosquitoes to prevent diseases like Zika

Hundreds of millions of genetically modified mosquitoes will soon be released in the Florida Keys island chain to wipe out local populations of disease-carrying mosquitoes, according to news reports.

The big questions are, will it work and will it have unintended effects on the environment?

The Florida Keys Mosquito Control District currently budgets about $1 million a year to combat the invasive Aedes aegypti mosquito, which can carry diseases like Zika virus and dengue fever and pass them on to humans, according to Gizmodo. In comparison to costly mosquito control tactics, such as aerial spraying of insecticides, the plan to release 750 million genetically modified mosquitoes to mate with local A. aegypti may be less expensive and more effective, according to the board.

“The science is there. This is something Monroe County needs,” mosquito board member Jill Cranny-Gage told The Associated Press. “We’re trying everything in our power, and we’re running out of options.” The board voted 4-1 in favor of the plan and will begin releasing the mosquitoes sometime next year.

But not everyone agrees that the science is up to snuff.

The biotech company Oxitec, which designed the modified pests, did so by introducing a “lethal gene” into male A. aegypti mosquitoes, Live Science previously reported. In theory, the modified males should mate with female mosquitoes and pass the lethal gene on to female offspring, causing the offspring to die before reaching maturity because they cannot properly build an essential protein. This same genetic change does not affect male survival, so the Oxitec mosquitoes survive to mate with females, according to Science Magazine.

Only female mosquitoes bite humans, as they need the blood to produce and mature their eggs, while male mosquitoes only drink nectar and therefore don’t infect people with deadly diseases, Gizmodo reported. In lab studies, Oxitec found that about 3% of female offspring with the lethal gene survive to adulthood, but these survivors are too feeble to produce offspring, Live Science previously reported.

However, that trend may not hold true in the wild.

When Oxitec released millions of the mosquitoes in Jacobina, Brazil between 2013 and 2015, genes from the modified pests cropped up in local mosquito populations, indicating that some female offspring survived long enough to mate and pass on their genes, according to a 2019 study published in the journal Scientific Reports. These resulting hybrid mosquitoes did not carry the lethal gene introduced by Oxitec, but instead carried genes from the original Cuban and Mexian mosquito populations first used to create the genetically modified mosquitoes.

The study authors speculated that, due to the increase in genetic variation, this hybrid mosquito might be “more robust,” meaning that the bug might be more resistant to insecticides compared with native populations. At the time, Oxitec requested that the authors’ “misleading and speculative statements” be reviewed by the journal, Science Magazine reported.

At this point, scientists don’t know how an influx of hybrid mosquitoes might affect humans or animals sharing an environment with the pests. Some argue that the Oxitec mosquitoes, themselves, may also harm local wildlife in unintended ways. “An ecosystem is so complicated and involves so many species, it would be almost impossible to test them all in advance in a lab,” Max Moreno, an expert in mosquito-borne diseases at Indiana University who is not involved with Oxitec or the pilot project, told the AP.