Rural California hatches a mosquito plan designed to fight an invisible predator

Rural California hatches a mosquito plan designed to fight an invisible predator

Brian Ruiz moved his family into a newly built house in this Central Valley agricultural hub seven months ago, and almost immediately found they were being assaulted.

Mosquitoes bite and harass them in broad daylight. He looked around, trying to find a source of water where they were breeding, and noticed a freshly dug pipe, intended to drain the water from the backyard to the front. He raised his hat and found inside a small puddle in the drain line, which had not enough slope to empty it completely.

Grab a turkey rod and pull the water, he already knows what he’s going to find: larvae Aedes aegyptiOne of the greatest threats to humans on this planet.

Ruiz knew what he was looking for as he was in charge of a newly formed team that would spend the summer months traveling around the northern county of Tulare to combat an invasion Aedes aegyptiMosquitoes are capable of infecting humans with deadly diseases such as dengue, chikungunya, yellow fever and Zika.

Since gaining a foothold in California less than a decade ago, Aedes aegypti It quickly spread across the state, and its territory now ranges from the desert terrain of Imperial County on the US-Mexico border to the wooded town of Redding in Shasta County, about 750 miles north.

To fight EgyptianMosquito control districts are relying on the same tools they have been using for decades — insecticides and eradication of water sources — even as climate change and agricultural practices allow mosquitoes to thrive in previously uninhabitable places.

But Tulare County officials hope the area will soon become a testing ground for a new generation of technology, including genetically modified mosquitoes, as they try to prevent the type of outbreak now common in the Caribbean and Central and South America where Aedes aegypti diffuse.

The most immediate mosquito threat in Tulare County comes from a different race, Colex, a species that usually bites at dawn and dusk and can carry West Nile virus, St. Louis encephalitis, and Western equine encephalomyelitis virus, all of which can be fatal. Over the past decade, California has recorded more than 4,000 West Nile cases and at least 220 deaths. Tulare’s mosquito control districts have poured significant resources into that fight, including releasing a range of chemicals, maintaining a hatchery for fish that feed on caterpillars, and most recently, purchasing a drone to transport the insecticides deep into the cornfields.

Aedes aegyptiHowever, it is a growing concern and much more difficult.

To understand this battle, you first have to understand how stealthy it is Aedes aegypti he is. Mosquitoes can lay their eggs in small spaces like a bottle cap, and the females spread their eggs across multiple sites—scientists often refer to their “hidden habitats.” Most other mosquito eggs need water to survive, but Aedes aegyptiIt can remain dormant for several months, and then come to life when the water finally comes. A mosquito can bite multiple times, repeatedly snack on the same person, or pass from one mosquito to another. You become a deadly threat if one of these people happens to be carrying dengue fever or some other virus.

In an increasingly globalized world, people regularly travel to places where dengue is endemic and bring it back to the United States. If they are bitten by a mosquito, the disease can spread locally. That’s what happened in the Florida Keys in 2020, and more than 70 people were infected before the outbreak was stopped.

California has so far avoided an outbreak of the disease it transmits Aedes aegypti. But it does import cases — California has recorded seven cases of imported dengue this year — and with mosquito numbers on the rise, experts say it’s likely only a matter of time.

Aedes aegypti He is a frequent traveler who travels around the world in freight. No doubt it has been introduced to California millions of times. It was only recently, said Chris Parker, associate professor of pathology, microbiology and immunology at UC Davis. It was first discovered in 2013 in three California cities: Menlo Park, Clovis, and Madeira.

today, Aedes aegypti It has spread to more than 200 California cities and 22 counties. It has strained mosquito control areas. “It was a lot of extra work, extra hiring, extra financial demand,” Parker said. “Aside from the risks of disease, the big issue is annoying biting.”

Because of the threat posed by mosquitoes, and when Egyptian It was discovered in 2014 by Delta Mosquito and Vector Control District, where Ruiz works, and the area rushed to eliminate the danger. The method of eradicating it required searching in every nook and cranny in the area where it is located Aedes aegypti Have taken residence and cleaned the water sources several times a week. Assistant District Administrator Meir Bear-Johnson said people were very upset with the completed press. This was a problem, because the area relies in part on reports from residents to know where the mosquitoes are.

The resection was also short-lived. In 2015, Aedes aegypti It was reintroduced, and this time the ferocious tick spread all over Visalia, the largest city in the region. Because Aedes aegypti Now that it can be found throughout the Central Valley, extirpation no longer seems an option, said Mustapha Debon, an entomologist who moved from Harris County, Texas, in March 2020 to command Delta.

Aedes aegypti Mosquitoes in the area are also widely resistant to pyrethroids, the family of chemicals most commonly used to kill adult mosquitoes. Pyrethroids are used extensively among agricultural companies in the area, and likely contribute to what Parker described as nearly 100% resistance.

That is why Debon and his colleagues are interested in genetically modified mosquitoes. They hope that engineered mosquitoes will reduce the number of wild animals Aedes aegypti Where they reproduce and produce short-lived offspring.

The US Environmental Protection Agency recently approved a trial in Tulare for mosquitoes designed by a company called Oxitec. The company says its latest product only releases male mosquitoes, which unlike females don’t bite. Mosquitoes are genetically modified to carry a “self-limiting” gene that is passed on during breeding and theoretically prevents offspring from surviving to adulthood. They have been released in several places, including Brazil and the Cayman Islands.

They were also released in the Florida Keys last year. There, Oxitec faced opposition from some homeowners worried about the unexpected risks of releasing genetically modified pests into the wild. Local officials put the issue on the 2016 ballot, and county residents, who had faced dengue and Zika virus, voted to go ahead.

Now, Oxitec and the Mosquito Delta Region are waiting for permission from the California Department of Pesticide Regulations to release the insects. Debon said the work will be funded by Oxitec with operational assistance from its employees.

The goal is to build on previous research that shows that the rate Aedes aegypti It temporarily reduces wild mosquito numbers but has left scientists with questions about broader impacts on the environment and how successful long-term efforts to curb the disease will be. Among the unknowns is whether Oxitec mosquitoes are actually unable to produce viable offspring from wild females.

Another question is what happens when Oxitec mosquitoes encounter tetracycline in the wild, said Parker, the expert at the University of California, Davis. Tetracycline is an antibiotic commonly used to control infections in livestock and agriculture, both of which are found in abundance in the Central Valley. Oxitec mosquitoes are bred with a type of shutdown switch that shuts off the self gene when it comes into contact with tetracycline. In the lab, this kill switch allows the company to breed engineered mosquitoes. If it is run in the wild, the concern is that the mosquito offspring will not die.

On a broader level, Parker said, he hopes California will pursue the experiment independently. He is one of the researchers interested in leaving this analysis in the hands of a private company that benefits from it. “If an independent source and the company are in agreement when all the findings are completed, that would have much more power and much greater potential in the future,” Parker said.

Rajiv Vidyanatan, Oxitec’s director of US operations, said the Delta Mosquito District in Tulare and Vector Control District were among several areas interested in hosting the trial. One selling point was Debon’s enthusiasm for new technologies.

Debon previously helped run a trial in Houston of a product called MosquitoMate, which releases male mosquitoes infected with the bacteria. Wolbachia. When mosquitoes breed with wild females, they produce eggs that do not hatch. This mosquito was also tested in Fresno County in 2018 and 2019 and led to a 95% reduction in females Aedes aegyptiAccording to an experimental study. However, that mosquito district told The Fresno Bee that she did not have the money to continue the project on her own.

“These are great, great options,” said Eva Buckner, an assistant professor at the University of Florida who advises mosquito control areas in Florida. “I think they have a lot of potential.” She wants to know what the cost-benefit ratio might be more widely used by government agencies compared to other interventions — a question Tolar’s research can help determine. And she warned that no matter the price, there would be no panacea for mosquitoes, which have suffered on Earth for millions of years.

Vaidyanathan said Oxitec wanted to test its technology in the arid regions of central California, because it could show it could work all over the world. Aedes aegyptiinvaded the southwest. Oxitec hopes its mosquitoes will eventually be sold to mosquito control areas in the United States, and directly to American consumers. This option is already available in Brazil, via a consumer subscription service that costs $10 to $30 per month. In the US prototype, the mosquitoes came in a hexagonal box decorated with playful insects. If all goes as planned, consumers will only add water, and the mosquitoes will come alive.

This story is produced by KHN, which publishes California Healthline, an independent editorial service of the California Health Care Corporation.

This article is reprinted from khn.org with permission from the Henry J. Kaiser Family Foundation. Kaiser Health News, an editorially independent news service, is a program of the Kaiser Family Foundation, a nonpartisan health care policy research organization not affiliated with Kaiser Permanente.

2022-05-10 11:07:00

Leave a Comment

Your email address will not be published. Required fields are marked *