In Los Angeles, those combatting mosquitoes are incorporating an additional tool into their arsenal: additional mosquitoes.
The Greater Los Angeles County Vector Control District initiated a trial program on Thursday to release tens of thousands of irradiated, lab-bred mosquitoes into the local ecosystem. These mosquitoes, all male, have undergone sterilization via radiation. The aim is for them to locate wild female counterparts and fertilize them with non-viable sperm, rendering the resultant eggs useless.
The focus is on a specific species, Aedes aegypti. These insects, which began infesting Los Angeles County in 2014, have adapted to target one primary thing: humans.
“Centuries ago, a variety of Aedes aegypti migrated near human settlements and adapted to thrive in close proximity to homes, targeting human blood,” remarked Daniel Hahn, a professor in the University of Florida’s Department of Entomology and Nematology. “They’re noted for being persistent nuisances as they feed on human blood throughout the day.”
Aedes Aegypti flourish in residential areas and nestle in small receptacles such as bottle caps and pet bowls. They can transmit concerning illnesses like yellow fever, Chikungunya, Zika, and dengue.
“We are aware of the suffering experienced by our residents,” stated Susanne Kluh, the general manager of the Greater Los Angeles County Vector Control District, which caters to 6 million individuals and boasts over 90 full-time employees.
The district released approximately 20,000 sterile male mosquitoes, marked with fluorescent dye visible under ultraviolet light, as the concluding phase of its pilot program assessment. Since male Aedes Aegypti do not feed on blood, experts assert that the program poses minimal risk to humans.
In the coming month, the district intends to release seven to ten sterilized mosquitoes for every wild male believed to inhabit the targeted region, namely the Sunland-Tujunga area of L.A. This could equate to up to 60,000 mosquitoes per week.
This approach exemplifies how humans are employing innovative technology to combat the proliferation of invasive mosquitoes and the diseases they transmit, spurred by factors like climate change, global commerce, and urban development.
“They have evolved to specifically exploit humans as their hosts, hence we are engaged in a perpetual arms race against them,” Hahn explained.
An expanded range for aggressive mosquitoes
The Aedes Aegypti mosquito is not indigenous to the United States but has established itself in certain areas for centuries. It has even played pivotal roles in American history: In 1793, it compelled several federal officials to evacuate Philadelphia, the then capital of the U.S., due to a yellow fever outbreak.
In recent times, scholars have cautioned that elevated temperatures attributable to climate change will extend the species' territory. This phenomenon seems to have occurred in Southern California.
Last year, the state documented its initial two instances of locally contracted dengue fever, indicating that indigenous mosquitoes were transmitting the virus.
“Previously, it was often stated that our climate wasn't conducive, but mosquitoes adapt, and our climate has shifted,” remarked Kluh. “We experience greater humidity in the summer, and individuals create these optimal little humid microclimates in their yards, complete with lush vegetation and the like.”
Moreover, the area has witnessed urban and suburban expansion, enlarging the habitat for Aedes Aegypti.
Fighting mosquitoes with mosquitoes
The militarized mosquitoes were cultivated in a laboratory in Kentucky but originated from eggs procured from the L.A. vicinity. Every week, the vector district intends to incubate mosquitoes in diminutive insect quarters before subjecting them to a burst of radiation from a specialized apparatus. Upon release, the irradiated mosquitoes will only travel approximately 150 meters, as per Kluh.
Hahn, who is not affiliated with the L.A. initiative, explained that the radiation burst disarrays the chromosomes within the mosquitoes' cells, halting reproduction while allowing the insects to fly and carry out other biological functions at nearly normal levels.
Kluh assured that the mosquitoes would not be radioactive and would not pose any risk to the public.
The district has allocated approximately $255,000 from its $24.8 million annual budget for the program, she added, stating, "We've managed to implement this economically."
However, Kluh acknowledged that expanding the program across more of Los Angeles County would pose a challenge. Instead, she envisions it as a focused intervention for Aedes Aegypti hotspots and regions where instances of mosquito-borne diseases are reported.
Similar technology is being pursued in other areas. In Florida, Lee County initiated a program to release sterile, irradiated mosquitoes in 2017. Additionally, various other California districts are testing the program or have invested in irradiation equipment.
New approaches to pest control
The concept of irradiating pests to reduce populations is not novel. Hahn stated that the agricultural sector has been subjecting male fruit flies to irradiation for roughly three decades.
Mosquito programs were conceived four decades ago, he noted, but eventually fell by the wayside due to being economically unfeasible.
Nevertheless, since then, mosquitoes have developed resistance to certain conventional pesticides, necessitating the exploration of new remedies.
Several companies are exploring alternative technologies to combat Aedes Aegypti, such as genetically modifying male mosquitoes to exterminate females, releasing male mosquitoes carrying specific bacteria, or introducing a dominant gene into the population to diminish numbers.
Hahn remarked that while some of these concepts entail risks of unintended repercussions, they warrant investigation nonetheless. These technologies are overseen by the Environmental Protection Agency, and several are undergoing trials in small-scale pilot programs.
In contrast, irradiation programs are not subject to regulation, rendering them the preferred method in the U.S. at present.
"We wanted to initiate something promptly," Kluh remarked.
