Farms across California have had to euthanize several million chickens and ducks in recent weeks, as a wave of avian influenza threatens to upend national poultry and egg supplies.
While cases of the disease have been cropping up throughout the U.S., agricultural hubs in Northern California have endured the greatest losses over the past month.
“There’s economy of scale in commercial agriculture, including poultry,” Maurice Pitesky, an avian disease specialist at the University of California Davis School of Veterinary Medicine, told The Hill.
“No pun intended — if you put your eggs all in one basket, the virus gets into a facility and then all the birds have to be euthanized, unfortunately,” Pitesky said.
As of midday Friday, about 10.62 million birds in 63 flocks nationwide had been affected by highly pathogenic avian influenza (HPAI) outbreaks over the past 30 days, according to the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service (APHIS).
Of these flocks, 37 were commercial and 26 were backyard, and a total of 3.8 million birds were concentrated in California.
The current spike in HPAI — on the rise since mid-fall — is the latest escalation in a nationwide outbreak that has ebbed and flowed since 2022.
A previous surge in the disease rattled the nation’s poultry industry last year, leading to national egg shortages and record-high price tags. The country could be headed in that direction again: While egg prices are still half of what they were about a year ago, they have risen 12 percent over last month, according to The Wall Street Journal.
Cal-Maine Foods, the country’s biggest egg producer, cited a 91 percent loss in profits in its Fiscal Year 2024 second quarter earnings — generating $17 million in quarterly net income, as opposed to $198.6 million during the same period last year.
Max Bowman, Cal-Maine’s vice president and chief financial officer, acknowledged the need to improve “biosecurity measures to mitigate the risk of highly pathogenic avian influenza,” in a statement accompanying the report.
HPAI is typically introduced into the U.S. from wild birds that migrate along the East Asian Flyway and cross paths with birds traveling along the North American routes, according to UC Davis’s Western Institute for Food Safety & Security.
Pitesky described migratory birds as “the primary reservoir” for HPAI, noting that ducks and geese often travel thousands of miles — meeting during fall in the Arctic, before heading south.
“When all those different flyways interface with each other, that’s where you get all these exchange[s] of viruses,” he said.
While wild waterfowl often carry the virus without developing symptoms, spread to domestic poultry can result in what institute researcher Michael Payne described in a statement as “catastrophic mortality.”
“It doesn’t take much,” Payne warned. “A drop of manure from an infected bird weighing only a gram, about the same as a dime, contains enough virus to infect one million birds.”
Two strains of HPAI, which attack multiple organs in chickens, come with up to 90-100 percent mortality rates and can cause death within 48 hours, according to the Centers for Disease Control and Prevention (CDC).
Although sporadic human infections have occurred with various bird flu viruses, they have typically happened only after prolonged, unprotected contact with sick birds, per the CDC.
California’s Central Valley hosts about 500-600 commercial poultry farms, as well as robust habitats for both non-migratory and migratory waterfowl, according to Pitesky. This domestic-wild combination, he explained, has created a “spatial interface” for disease transmission.
Exacerbating that clash, Pitesky said, are the dual threats of human development and climate change — which have collectively caused shifts in the proximity of waterfowl to these farms.
The five California counties that currently have active infections of HPAI include Sonoma, Marin, Merced, Fresno and San Joaquin, the California Department of Food and Agriculture determined in a recent investigation.
“To protect other flocks in California, the locations of the detected infected flocks are currently under quarantine, and the birds are euthanized to prevent further disease spread,” the department said.
Sonoma County last month declared a state of emergency following the detection of HPAI at two commercial poultry farms in the southern portion of the county. To protect other flocks in the region, those locations were put under quarantine and about 250,000 birds were euthanized.
Such action served to prevent further disease spread, but also came at the expense of the local agricultural economy, Sonoma County Supervisor David Rabbitt said in a statement at the time.
Southern Sonoma County poultry farms supply “hundreds of thousands of eggs each and every day,” which in turn bolsters the “food chain for the entire West Coast if not beyond,” he added.
More recently in Sonoma County, about 494,200 birds were affected by HPAI at a commercial table egg layer farm, according to APHIS.
A similar fate befell 54,000 and 37,300 birds located at two such farms on Dec. 28, per the APHIS data. On the same date, the disease was also detected in Marin County, impacting 151,000 birds at a table egg pullet farm — a farm that houses immature laying hens.
More than 2.3 million birds residing at multiple Merced County table egg layer farms were affected by the disease during December, the data determined.
Also impacted throughout these counties have been broiler chickens, ducks and turkeys.
Other states with reported outbreaks include South Dakota, Minnesota, Wisconsin, Kansas, Arkansas, Minnesota, Ohio and Pennsylvania.
Although some experts are calling for mass vaccination of poultry to prevent the spread of the disease, Pitesky said that this is currently impractical from both a financial and logistical perspective, as there would be a need to process some 8 billion broilers and more than 350 million egg-laying hens annually.
Also complicating matters are associated political tensions: Some vaccinated birds might have no symptoms but still be capable of transmitting the disease, he explained. At the same time, the U.S. remains one of the top poultry exporters in the world.
“The way that trade works is once you start vaccinating, it becomes much more difficult to differentiate vaccinated infected birds from uninfected birds,” Pitesky said.
As the disease continues to rip through California and other regions around the globe, however, the World Organization for Animal Health (WOAH) called for the reconsideration of “all available tools” to reduce pandemic risks, including vaccination.
Arguing that sanitary control measures may be insufficient to curb the spread of HPAI strains, the group pushed to include vaccination among disease prevention strategies.
Opting for such action, the group stressed, would require not only high-quality vaccines that meet international standards, but also robust surveillance protocols, a compliance commitment from poultry producers and traceability of every step of the process.
Although four HPAI vaccines are licensed in the U.S., none have been approved for the most virulent strain, according to the American Veterinary Medical Association. Meanwhile, the USDA has completed initial testing on five HPAI vaccine candidates but is still evaluating their efficacy.
“Ultimately, that trade rules and regulations might have to change,” Pitesky said, noting that Australia remains the only continent that is currently free of bird flu.
“Everyone’s kind of getting hammered by it,” he added. “So we might have to revise some of those rules are ultimately in order to facilitate trade.”
As far as the future is concerned, Pitesky said that he and his team are working on developing remote sensing tools that can indicate where waterfowl are with respect to commercial poultry.
He voiced support for restoring waterfowl habitats at a farther distance from existing poultry farms, while acknowledging that certain areas and geographies might not be suited for organic or pastured poultry cultivation.
Describing the ongoing outbreak as “an existential issue,” Pitesky stressed that poultry remains the top-consumed animal protein nationwide.
“We can’t keep on having this happen every year, where we’re having to euthanize and depopulate millions of birds — from a welfare perspective from an economic perspective,” he said.
“There is value in having large farms, but I also think we need to be very thoughtful about where we have those large farms,” Pitesky added.