LA releases thousands of sterile male mosquitoes to ward off aggressive female mosquitoes

In Los Angeles, those fighting a war against mosquitoes have added to their arsenal: more mosquitoes.

The Los Angeles County Metropolitan Mosquito Control District on Thursday began a pilot program that will release tens of thousands of irradiated, lab-raised mosquitoes into the local environment. These mosquitoes are all male and have been sterilized by radiation, so the hope is that they will find wild female mates and impregnate them with dead-end sperm, rendering the resulting eggs worthless. .

The target is a specific species, Aedes aegypti. This insect, which began inhabiting Los Angeles County in 2014, has evolved to focus on one thing: you.

“Several thousand years ago, a species of Aedes aegypti invaded humans and began to specialize in living near homes and biting people,” said Daniel Hahn, a professor in the Department of Entomology and Nematology at the University of Florida. “They are characterized as aggressive and nuisance biters because they bite throughout the day.”

Aedes aegypti breeds in backyards and makes their home in small containers such as bottle caps and dog bowls. They can transmit alarming diseases such as yellow fever, chikungunya, Zika, and dengue.

“We know our residents are suffering,” said Suzanne Crews, general manager of the Los Angeles County Urban Vector Virus Response District, which serves 6 million people and has more than 90 full-time staff. .

On Thursday, the district released about 20,000 sterile male mosquitoes that were dyed to appear fluorescent under blacklight as part of the final pilot program test. Male Aedes aegypti mosquitoes do not bite, so experts say the program poses virtually no risk to humans.

Next month, the district plans to release 7 to 10 sterile mosquitoes per wild male believed to live in Los Angeles' Sunland-Tujunga area, up to 60,000 per week. may reach.

This strategy reflects how humans are deploying new technologies to combat the spread of invasive mosquitoes and mosquito-borne diseases, as climate change, global trade, and urbanization push pests into new areas. This is an example.

“They have evolved specifically to exploit humans as hosts, so we are in a constant arms race with them,” Hahn said.

Expanding the range of aggressive mosquitoes

Aedes aegypti is not native to the United States, but it has been present in some areas for hundreds of years. They have also played a central role in American history. In 1793 they forced some federal agents to flee Philadelphiadue to an outbreak of yellow fever when the city was the seat of the U.S. government.

In recent years, researchers have warned of rising temperatures due to climate change. will expand the range of species. That seems to be what happened in Southern California.

The state recorded that First two locally transmitted cases of dengue occurred last yearThis means that local mosquitoes were transmitting the virus.

“Everyone always said our weather wasn't suitable, but you know the mosquitoes adapted and our weather changed,” Crews said. “It's humid in the summer, and people plant their backyards with leafy plants and everything to create the ideal little humid mini-climate.”

The region has also seen urban and suburban sprawl, expanding habitat for the Aedes aegypti mosquito.

fight mosquitoes with mosquitoes

The weaponized mosquito, bred in a Kentucky lab, was developed from eggs sourced from the LA area. Vector districts plan to incubate mosquitoes in small insect dormitories every week and then irradiate them with special machines. Once released, the mosquitoes can only fly about 150 meters, Crew said.

Hahn, who is not involved in the Los Angeles project, said the radiation blast shreds the chromosomes inside the mosquito's cells, preventing them from reproducing while allowing the insects to fly at near-normal levels and perform other biological functions. He said he would do so.

Crews said the mosquitoes are not radioactive and pose no danger to the public.

The district spends about $255,000 of its $24.8 million annual budget on the program, adding, “We did this on the cheap.”

Still, Crews said it would be difficult to expand the program across Los Angeles County. Instead, she envisions treatments targeting Aedes aegypti hotspots and areas where cases of the mosquito-borne disease have been reported.

Other regions are pursuing similar technologies. In Florida, Lee County started a program in 2017 to release irradiated, germ-free mosquitoes. Several other California districts are also piloting the program or purchasing irradiators.

A new approach to pest control

The idea of ​​irradiating pests to reduce their populations is not new. The agricultural industry has been irradiating male fruit flies for about 30 years, Hahn said.

The mosquito program was developed 40 years ago but ultimately “was left behind because it wasn't cost-effective,” he said.

But since then, mosquitoes have evolved to resist some common insecticides, creating the need for new solutions.

Some companies are pursuing other technologies to combat Aedes aegypti. Examples include genetically modifying male mosquitoes to kill females, releasing male mosquitoes that carry specific bacteria, or injecting dominant genes into a population to reduce their numbers.

Hahn said some of these ideas come with risks of unintended consequences, but are still worth exploring. Such technologies are regulated by the Environmental Protection Agency; Some are being tested in small pilot programs.

However, irradiation programs are unregulated, making them the weapon of choice in the United States today.

“We wanted to start something now,” Crews said.

This article was first published NBCNews.com