Genetically modified mosquitoes are headed to San Joaquin Valley. Should that bug you?
How do you keep an invasive, aggressive, pesticide-resistant species of mosquito in check?
Genetic engineering could provide an answer, and the central San Joaquin Valley will soon be the testing ground for a somewhat controversial field trial following the Environmental Protection Agency approval of an experimental use permit to a British biotechnology firm.
Developed by Oxitec, millions of genetically modified male Aedes aegypti mosquitoes, which don’t bite, are released into the wild to breed with wild females responsible for biting and transmitting diseases such as dengue, Zika and chikungunya to humans. The altered male mosquitoes carry a self-limiting gene that passes on to their offspring, kills female progeny in early larval stages and, at least in theory, serves to reduce the species’ overall numbers.
The pilot program still requires authorization from the California Department of Pesticide Regulation. If granted, Mustapha Debboun, general manager of the Delta Mosquito and Vector Control District, expects the first batch of genetically modified male mosquitoes to be released in May.
The Delta Mosquito district, which spans northern Tulare County including Visalia, was selected for the experimental field trial out of 10 California mosquito abatement districts that applied, according to an Oxitec media release.
“My goal is to protect people from mosquito-borne diseases and other vector-borne diseases, and I’m always looking for new techniques to augment what we have,” Debboun said.
“We don’t always have to use pesticides, chemicals, that these mosquitoes develop a resistance to. That’s why you need to develop other tools to help us fight them.”
Following a five-year approval process, Oxitec began testing its genetically altered Aedes aegypti mosquitoes last year in the Florida Keys. In expanding the firm’s experimental use permit to California (it covers 29,400 acres in four counties through April 30, 2024), the EPA also identified the reduction of pesticide use as a potential helpful result.
“This may be especially beneficial for densely populated communities with environmental justice concerns,” the EPA’s news release stated.
However, as with anything involving genetic modification, the technology is not without its critics.
Health, environmental impacts questioned
No sooner did the EPA announce its approval Monday than objections began to pour in. A news release by the environmental group Friends of the Earth highlighted the potential impacts on human health and endangered species, which the nonprofit claims haven’t been studied, as well as redactions in Oxitec’s data and results from previous trials in Florida and other countries.
Furthermore, the group cited a peer-reviewed Yale University study that found two years of continual releases of genetically engineered mosquitoes at an Oxitec test site in Brazil failed to reduce Aedes aegypti populations.
“Scientists have found genetic material from GE mosquitoes in wild populations at significant levels, which means GE mosquitoes are not sterile. GE mosquitoes could result in far more health and environmental problems than they would solve,” said Friends of the Earth’s Dana Perls, who called on the EPA to conduct a thorough review of the potential risks.
In its media release, the EPA stated data submitted by Oxitec demonstrated that its genetically modified mosquitoes met federal standards of “not causing unreasonable adverse effects to humans or the environment.”
Oxitec, meanwhile, claimed its technology “does not harm beneficial insects like bees and butterflies and is proven to control the disease transmitting Aedes aegypti mosquito.”
California is home to more than 50 established species of mosquitoes. But until 2013 the list did not include Aedes aegypti, those pesky “ankle biters” that feed during the day. Unlike other mosquitoes, Aedes aegypti don’t need standing water or snowmelt to reproduce. Females often lay their eggs on the dry walls of containers — even those as small as a flowerpot saucer. The eggs can survive up to eight months until they hatch when it rains or are covered in water, according to the federal Centers for Disease Control.
Officials in the Florida Keys blame Aedes aegypti for nearly all the mosquito-borne diseases transmitted to humans in their region. The same isn’t true in California, or at least not yet. The few cases of Zika or dengue fever diagnosed here are linked to bites in other countries or sexual transmission.
“All it takes is one,” said David Brown, technical adviser for the American Mosquito Control Association.
Previous Fresno-area trials
This isn’t the first time a local abatement district has participated in an experimental trial aimed at curtailing Aedes aegypti. Between 2017-19, the Clovis-based Consolidated Mosquito Abatement District partnered with a Kentucky-based biotech firm and the research company Verily on a study (aptly named Debug Fresno) that introduced sterile males to wild females.
However, the male mosquitoes employed in that trial — more than 15 million were released in batches at Harlan Ranch, Loma Vista, Fancher Creek and other locations — were not genetically engineered or modified. That is a fact, no matter what you read on Nextdoor.
Rather, those mosquitoes were infected with a Wolbachia bacterium that rendered them sterile.
According to Jodi Holeman, Consolidated Mosquito Abatement District’s supervisor of operations, the experiment proved highly successful — biting females were reduced in number by more than 95 percent during peak season — but still awaits EPA approval.
Debboun, GM of the Visalia-based Delta Mosquito district partnering with Oxitec, called the firm’s technology “very encouraging” and insisted the trial will adhere to strict federal guidelines.
“I don’t want to just rely on pesticides because after mosquitoes develop resistance to them, then we have a problem. Chemicals won’t work anymore,” Debboun said. “But by using an organism against another organism, that’s a natural thing. Send the mosquito out there to do the job for us.”
It’s fair to debate whether organisms that have their genes tinkered with in a laboratory are natural, and for the public to demand complete transparency. Does this technology actually work, and without negative unintended effects? We deserve better, more complete answers from both the EPA and Oxitec. But the ultimate goal of controlling an invasive insect without the use of chemicals is probably an experiment worth undertaking.
