‘Jurassic Park’ Genetically Modified Mosquitoes Actually Work

A pilot study in Florida that involved the release of 5 million genetically modified mosquitoes in Florida has wrapped up. The bugs, which have been dubbed “Jurassic Park” mosquitoes by some critics, were first released in April 2021 as part of a program with health officials in the Florida Keys to try to tamp down on the local mosquito population. The goal of the program is to have these genetically modified mosquitoes mate with wild mosquitoes to create offspring with a lethal gene that would kill future generations of the blood-sucking bugs, lowering the risk they would pass on certain diseases to humans.

Oxitec, the company that creates the genetically modified mosquitoes, announced earlier this month that the pilot program was a success. According to Oxitec, researchers collected more than 22,000 mosquito eggs from traps they set out and brought them back to their lab to hatch under observation. The researchers found that all female mosquitoes that inherited the lethal gene died before they became adults.

“Basically, the goal is to crash a specific mosquito population,” says Ben Hottel, technical services manager at Orkin.

The U.S. Environmental Protection Agency (EPA) has also approved a pilot project that will use the genetically modified mosquitoes in California’s Tulare County. But what are genetically modified mosquitoes, exactly, and how does this whole thing work? Here’s what you need to know.

What are genetically modified mosquitoes?

Genetically modified mosquitoes are mosquitoes that are created in a lab. “Genetically modified mosquitoes have genomes—the complete genetic material of an organism—that have been altered to make them into effective tools for controlling the spread of mosquito-transmitted pathogens,” says Eric Caragata, Ph.D., mosquito researcher and assistant professor at the University of Florida Institute of Food and Agricultural Sciences. “A mosquito genome contains many different genes that can be modified to reduce mosquito population size or to make mosquitoes more resistant to key pathogens, like dengue.”

GM mosquitoes are created using a technique called embryonic microinjection, Caragata explains. “This involves injecting freshly laid mosquito eggs with a very small needle containing engineered DNA, often called a transgene,” he says. “This engineered DNA or transgene integrates into the mosquito genome and specifically activates or inactivates a target gene.”

There are different type of genetically modified mosquitoes out there but, in this particular case, they contain a certain gene that kills their female offspring before they become adults. (Only female mosquitoes bite people—males eat flower nectar, Hottel says.)

These genetically modified male mosquitoes, which are Aedes aegypti mosquitoes and called OX5034, don’t bite and mate with female mosquitoes that are in the wild to pass on the gene, Oxitec explains in a press release.

The genetically modified mosquitoes also contain “a fluorescent marker gene that allows researchers to identify these mosquitoes in the wild,” explains Tom Dobrinska, a board certified entomologist with Ehrlich Pest Control.

The World Health Organization (WHO) breaks down different types of genetically modified mosquitoes, noting that they can be effective through the following measures:

• Passing on a lethal gene to females
• Creating a gene that makes it more likely that baby mosquitoes will be male (and therefore less likely to bite people)

Why are they releasing genetically modified mosquitoes?

Aedes aegypti mosquitoes can carry and pass on serious diseases, including dengue, Zika virus, and chikungunya in the U.S. In 2019, the Florida Keys had its first outbreak of dengue in a decade and 56 people were infected with the disease, according to Keys Weekly.

“Effective vaccines are not available for most of the diseases caused by Aedes aegypti-transmitted viruses, so disease prevention currently relies on controlling Aedes aegypti mosquito populations,” Caragata says. “However, our current control methods are not perfect.”

“It’s hard targeting Aedes aegypti, which rests close to homes and flies during the day, with traditional mosquito control techniques,” says Rajeev Vaidyanathan, director of U.S. Programs at Oxitec. “We use male mosquitoes to find female mosquitoes—so our boys are better than a pesticide cloud—and they target the one species of concern.”

This isn’t the first time genetically modified mosquitoes have been used. Genetically modified mosquitoes were released in Brazil and caused a 95% reduction in the local Aedes aegypti mosquito population. They were also used in two islands in China and reduced the female Asian tiger mosquito population by up to 94%, according to one study.

When used properly, the WHO says that genetically modified mosquitoes can do a range of different things, including creating protection over a large area, reducing the use of pesticides, and lowering the likelihood that certain diseases will spread.

What is the problem with genetically modified mosquitoes?

It’s not clear at the moment if there is one. The World Health Organization (WHO) seems largely in favor of the practice, saying in guidance released in May 2021 that “genetically modified mosquitoes could be a powerful and cost-effective tool to supplement existing interventions.”

It’s important to note, though, that genetically modified mosquitoes “only work on one target species of mosquitoes and not any other type,” Dobrinska says. “Most areas have much more than one mosquito species,” he adds.

Critics point out that it’s hard to say exactly what impact these mosquitoes will have. “What could possibly go wrong? We don't know, because EPA unlawfully refused to seriously analyze environmental risks,” Jaydee Hanson, policy director for the International Center for Technology Assessment and Center for Food Safety, previously said in a statement.

Some critics are also worried that the modified mosquitoes will create wild hybrid mosquitoes that could actually increase the risk of mosquito-borne illnesses. One study published in 2019 found that a hybrid strain of these mosquitoes was created, although the researchers weren’t able to conclude how the new strain would impact mosquito-borne diseases.

In order for these programs to be effective, modified mosquitoes need to continue to be released, Dobrinska says. “When genetically modified mosquitoes stop being released, the Aedes aegypti population returns to previous levels prior to release,” he notes. “The release of genetically modified mosquitoes requires multiple release points and at continuous frequencies to be effective.”

One thing that isn't a concern, Caragata says, is disrupting the food chain. "The project is not expected to disturb the ecosystem," he says. "Aedes aegypti is not a natural part of the food web in the United States."

Genetically modified mosquitoes may be an effective strategy in lowering the risk of mosquito-borne illnesses in the future, Hottel says, but their use alone won’t protect everyone.

“A multiple control approach is probably best,” he says. “That means using this technology, along with habitat modification—emptying containers that have water, making sure you use screens in your windows, and cleaning out your gutters—and pesticide applications. All of those in combination would be the real solution.”