Billions of Genetically Modified Mosquitoes Are Set to Descend on California and Florida This Summer

Californians may not know it on sight, but there’s going to be something different about their mosquitoes this summer. An invasive species of the bite-prone insects has been genetically modified in an attempt at controlling disease spread.

According to Smithsonian, the Environmental Protection Agency (EPA) has approved plans by biotech firm Oxitec to release 2.4 billion male Aedes aegypti mosquitos in both California and Florida that have been altered so their genes can only participate in producing surviving male offspring. (Females will die before reaching adulthood.) The insects will be introduced as eggs, which will then hatch when exposed to water.

Because male mosquitoes do not bite, the theory is that a declining female mosquito population will reduce transmission of Zika, yellow fever, dengue, and other infectious diseases that can be passed on to humans from the bites. The goal is halting outbreaks before they begin.

In 2021, Oxitec released 144,000 genetically modified mosquitoes in the Florida Keys. The insects have also been introduced in Brazil, the Cayman Islands, Panama, and India. While there is no spread of such diseases in California, the firm says a growing mosquito population could eventually pose a problem and that such pilot programs are necessary to assess effectiveness.

Not everyone has expressed optimism in the program. Critics have said Oxitec has yet to release details of their findings from the Florida Keys. (Oxitec says they’re waiting for federal and state regulation processes to conclude.) Additionally, the genetic modification can apparently be neutralized by tetracycline, an antibiotic found in agriculture that could introduce variables in mosquito reproduction. Some fear the program could result in a hybrid that may prove more difficult to manage.

The EPA asserts such programs pose no risk to humans, animals, or the environment. Oxitec has said that while approval covers 2.4 billion mosquitoes, the actual number released will be less and limited to the Florida Keys and Tulare County in California.

While the EPA has cleared the program, the mosquitoes still need to be approved by California’s department of pesticide regulation.