In May 2020, the U.S. Environmental Protection Agency gave the greenlight to release hundreds of millions of genetically modified mosquitoes in the Florida Keys. I realize that sentence had a lot of scary buzzwords: mosquitoes, genetically modified, Florida. So, what’s the plan here, why are we doing this, and what are the potential risks?
Mosquitoes are more than just irritating pests that cause itchy bumps and make me dread going outside. They are also considered the deadliest animals in the world. The diseases they carry run the gamut from malaria to yellow fever, and their bites cause at least hundreds of thousands of deaths each year. Sharks, by comparison, kill about 4 people annually.
One mosquito species in particular, Aedes aegypti, can spread several diseases like dengue, zika, and yellow fever and is considered a serious threat to public health. So much so that the Florida Keys Mosquito Control throws over $1 million dollars and six pesticide spraying aircraft at them each year. Despite eating up about a tenth of their budget, these efforts only reduce the Aedes aegypti population by 30 to 50%.
So, years ago the local government came to the conclusion that they couldn’t go on spraying their way out of trouble, and in 2012 they contacted the company Oxitec.
At the time, Oxitec was developing a genetically modified male Aedes aegypti mosquito designated OX513A that would die before it reached adulthood – unless it developed in water containing the antibiotic tetracycline. The thinking was if these males matured in a lab and were then turned loose in the wild, they would mate and their offspring would inherit the modified genes and die in antibiotic-free standing water when they hatched.
Starting in 2009, Oxitec’s mosquitoes began testing in the Cayman Islands, Panama, and Brazil. But there were concerns about whether mosquitoes bred to survive only in the presence of antibiotics would spread antibiotic resistant bacteria. Others were worried about the consequences of some offspring surviving and passing on their modified genes. There’s a chance the offspring could survive if they hatched close to places like sewage treatment plants and citrus orchards where antibiotics can accumulate.
In the last few years, Oxitec has developed a new male mosquito that circumvents the issue of antibiotics. The updated breed, known by the designation OX5034, mates with wild females as before. But instead of the offspring all dying off, only the females die young. The male descendants that inherit the mutation can reach adulthood, mate, and continue the femicide for generations.
Oxitec claims the total number of modified males will decrease from one generation to the next, eventually disappearing from the population altogether after 10 generations. In case you were wondering, the lifespan of an adult Aedes aegypti mosquito is between two weeks to over a month.
So, why are they targeting the female mosquitoes in particular? Well, it’s because male mosquitoes don’t bite humans; instead, they can subsist off nectar. Only females draw blood because their eggs need it to mature, meaning that females are the ones who can spread disease. That’s why Oxitec’s plan to release 750 million mosquitoes into the Florida Keys isn’t as counterproductive as it sounds. They’ll all be male, so the company isn’t letting swarms of bloodsuckers loose on all of us.
Still, scientists have voiced concerns. Independent analysis of Oxitec’s early trials in Brazil with their antibiotic-dependent strain, showed that some offspring survived and mated again, passing on genes to the local mosquitoes. The genes that were passed on weren’t the transgenes that would kill offspring though, just markers that came from the Cuban and Mexican mosquitoes Oxitec bred to create their homme fatales. Oxitec thinks concerns are overstated, saying they found about 3% of offspring in lab trials were viable.
The company also claims there’s no evidence that cross-breeding strains would make the mosquitoes more harmful to humans or resistant to insecticides. But some scientists are worried making the gene pool more varied with DNA from other world regions would create hardier bugs. Others are also concerned that killing off large numbers of Aedes aegypti could affect the local ecosystem and the animals that feed on mosquitoes. But Aedes aegypti represent 1% of the Florida Keys mosquito population, and are likely an invasive species that came to the Americas by ship.
This latest release is also not something that has been decided on a whim; the EPA has spent years studying the impacts that Oxitec’s mosquitoes have on human and environmental health, and seven Florida state agencies have given the latest trial unanimous approval. The antibiotic-resistant mosquito variety was also assessed by the FDA and in 2016, they found it would have no significant negative impact.
This second generation genetically modified mosquito has also already been tested in Brazil, where it temporarily reduced the Aedes aegypti population by as much as 96%. Though the idea of intentionally releasing millions of lab-grown mosquitoes may sound like the plot of a B-grade horror movie to some, lots of research and care has been put into their development. And remember: their release into the wild is another phase in their testing. If the releases prove ineffective or harmful, plans for more widespread use can be nixed. Come 2021 — or 2022 — we’ll see if they can help fight the spread of disease and reduce the need to spray pesticides over the Florida Keys.