In Los Angeles, those waging war on mosquitoes are adding a weapon to their arsenal: more mosquitoes.
The Greater Los Angeles County Vector Control District on Thursday launched a pilot program to release tens of thousands of irradiated and lab-grown mosquitoes into the local environment. These mosquitoes are all males and have been sterilized by radiation, so the hope is that they will find wild females and impregnate them with dead-end sperm, rendering the resulting eggs useless.
The target is a specific species, Aedes aegypti. The insects, which began populating Los Angeles County in 2014, have evolved to focus on one thing: you.
“Thousands of years ago, a strain of Aedes aegypti got close to people and began to specialize to live near homes and bite people,” said Daniel Hahn, professor in the Department of Entomology and Nematology at the University of Florida. “They are characterized as aggressive and nuisance biters because they bite you all day.”
Aedes Aegypti thrives in backyards and makes its homes in small containers such as bottle caps and dog bowls. They can transmit worrisome diseases such as yellow fever, Chikungunya, Zika and dengue fever.
“We know our residents are suffering,” said Susanne Kluh, general manager of the Greater Los Angeles County Vector Control District, which serves 6 million people and has more than 90 full-time employees.
The district on Thursday released about 20,000 sterile male mosquitoes, dyed to appear fluorescent under a black light, as part of the pilot program’s final test. Male Aedes Aegypti mosquitoes don’t bite, so experts say the program poses almost zero risk to humans.
Next month, the district plans to release seven to 10 sterile mosquitoes for every wild male believed to live in the target region, the Sunland-Tujunga area of Los Angeles. This could reach 60,000 mosquitoes per week.
The strategy is an example of how humans are implementing new technologies to combat the spread of invasive mosquitoes and the diseases they can transmit, as climate change, global trade and urbanization drive pests into a new territory.
“They evolved specifically to exploit humans as their hosts, and so we are constantly in an arms race against them,” Hahn said.
An expanded range for aggressive mosquitoes
The Aedes Aegypti mosquito is not native to the United States, but has been in some regions for hundreds of years. They even played central roles in American history: in 1793, they forced some federal authorities to flee Philadelphiawhen the city was the seat of the US government, because of a yellow fever outbreak.
In recent years, researchers have warned that higher temperatures due to climate change will expand the range of the species. That appears to be what happened in Southern California.
The state registered first two cases of locally acquired dengue last yearwhich meant local mosquitoes were transmitting the virus.
“Everybody always said, well, our climate isn’t suitable, but you know, mosquitoes adapted and our climate changed,” Kluh said. “We get more humidity in the summer, and people create these ideal little humid climates in their backyards, with lush plants and everything.”
The region has also undergone urban and suburban expansion, which has expanded the habitat of Aedes Aegypti.
Fighting mosquitoes with mosquitoes
The armed mosquitoes were created in a Kentucky laboratory but developed from eggs sourced from the Los Angeles area. Every week, the vector district plans to hatch mosquitoes in small insect dormitories and then blast them with radiation from a specialized machine. Once released, the irradiated mosquitoes will only fly about 150 meters, Kluh said.
Hahn, who is not involved in the Los Angeles project, said the blast of radiation severs chromosomes inside mosquito cells, preventing reproduction while allowing the insects to fly and perform other biological functions at near-normal levels.
Kluh said the mosquitoes will not be radioactive and will not pose a risk to the public.
The district spent about $255,000 of its $24.8 million annual budget on the program, she added: “We did it on the cheap.”
Still, Kluh said it would be a challenge to expand the program to more areas of Los Angeles County. Instead, she sees it as a targeted treatment for Aedes Aegypti outbreaks and areas where cases of mosquito-borne diseases are reported.
Other regions are pursuing similar technology. In Florida, Lee County began a program to release sterile, irradiated mosquitoes in 2017. Several other California counties are also testing the program or have purchased irradiators.
New approaches to pest control
The idea of irradiating pests to reduce populations is not new. The agricultural industry has been irradiating male fruit flies for about three decades, according to Hahn.
Mosquito programs were developed 40 years ago, he said, but in the end “they fell behind because they were not cost-effective.”
Since then, however, mosquitoes have evolved to resist some common pesticides, creating a need for new solutions.
Some companies are pursuing other technologies to combat Aedes Aegypti, such as genetically modifying male mosquitoes so they kill females, releasing male mosquitoes that carry a specific bacteria, or seeding a dominant gene in the population to reduce numbers.
Hahn said some of these ideas carry the risk of unintended consequences, but they are still worth researching. These technologies are regulated by the Environmental Protection Agency and some are being tested in small pilot programs.
But irradiation programs are unregulated, making them the weapon of choice in the US today.
“We wanted to start something now,” Kluh said.
This article was originally published in NBCNews. with
