In response to the increasing variety of cows infected with H5N1 avian influenza in California, state authorities have quarantined 34 dairies and are urging other farms to adopt similar biosecurity measures.
The milk supply is secure and the huThe risk to humans is low, state health officials say. Although 14 cases have been reported amongst farmworkers across the country, none have spread from individual to individual.rson. And none are in California.
But the sharp rise within the variety of infected herds – it has tripled from 10 to 34 across California's 1,000 dairies up to now week – is causing concern for the state's thriving dairy industry, which is a key a part of the state's agriculture sector and the country's largest milk producer.
“This is a difficult moment,” said Anja Raudabaugh, general manager of Western United Dairies in Turlock, since the state has worked for nine months to stay virus-free. “One violation was enough and it was a disaster.”
The rising variety of cases can also be causing concern amongst epidemiologists and health experts who monitor farm employees on infected farms.
The genetic mutation that allowed the virus to leap from birds to cows and other mammals brings it a step closer to an outbreak in humans, they are saying. The 1918 flu pandemic, which killed greater than 50 million people worldwide and sickened 500 million more, was attributable to a virus that originally got here from infected birds.
“I'm extremely concerned,” said John Korslund, a retired U.S. Department of Agriculture veterinary epidemiologist who studies livestock diseases. “In areas with high cattle populations like the Central Valley, the virus appears to be highly contagious between herds.”
“The virus is a great shape-shifter. Its behavior today is likely to change in the future,” he said. “We are at great risk of numerous outbreaks in poultry and of the virus being transmitted to workers, wild animals and livestock such as feral cats, rats and mice.”
An investigation continues to be underway into how the virus was introduced from outside the state, where 237 herds in 14 states are affected, said state veterinarian Dr. Annette Jones.
Genetic testing has shown that the virus was not brought in by a wild bird, but by equipment or cattle from other states, she said. One rumor is that California cattle were infected once they were transported to Idaho but then returned with fake travel documents. State law requires cows imported from infected states like Idaho to be tested and test negative.
Once a farm tests positive, it’s quarantined under the legal authority of the state veterinarian. This requires increased biosecurity and restricts the movement of cattle from the farm. Employees must change clothes when coming and going. The state also quarantines dairy farms which are inside ten kilometers of an infected herd or have contact with an infected herd.
Authorities are usually not disclosing the names of infected counties or dairies, although the primary cases reportedly occurred in Tulare County. Disclosing them would pose a biosecurity risk because curious onlookers could visit the farms, Jones said.
This frustrates some farmers.
“How can you stop something if you don't know where it is?” says Joe Bento of Valley Milk Simply Bottled in Modesto, which sells raw milk to customers within the Bay Area. “This is our livelihood. These are our customers. And this could close the dairy forever.”
In the event of poultry outbreaks, the placement will likely be announced, Korslund said. “The same courtesy should also apply to dairy herds.”
Every producer in California must assume that neighboring producers are infected or at high risk of infection, he said.
In the southern San Joaquin Valley, dairies are taking aggressive biosecurity measures, Raudabaugh said.
They keep out all non-essential visitors, equivalent to vendors. Roadblocks, equivalent to hay bales, delay traffic. Deliveries of medicines and other essential items are left in a protected location on the road outside the dairy. Livestock trailers are cleaned with a bleach solution using pressure washers before and after transporting livestock.
But within the northern parts of the valley, compliance with the regulations is more lax.
“We would like to see increased biosecurity on farms across the state,” Jones said.
Over the past 4 years, the deadly and highly contagious virus has circulated the globe, causing horrific losses amongst birds in over 80 countries.
After its emergence in 2020, the virus triggered major outbreaks in Europe, Africa and Asia. In January 2022, it reached the United States, spreading to the most important concentrations of poultry farms within the East and Midwest of the country.
A genetic evaluation by evolutionary biologist Michael Worobey of the University of Arizona found that there was probably a single transmission from birds to cows – probably in late 2023 in Texas.
As the virus spreads amongst cattle, the probabilities of a brand new mutation developing that causes more severe disease in cattle—or transmits the disease to humans—increase.
The more H5N1 spreads unchecked, the larger the “reservoir” becomes and the greater the prospect that further mutations will prevail, in response to the Scripps Research Translation's Institute. Eric TopolProfessor of Molecular Medicine.
Further research is required to know the transmission routes and clinical disease progression, Korslund said. Cows seem like most contagious to one another and to human employees before they grow to be unwell, so an infection will not be recognized immediately.
Further spread could reduce the state's milk, cheese and yogurt production. Treatment has improved in order that cows now not die from infection, but they have to be faraway from the milking rotation. Almost all the milk, cheese and yogurt within the state's school lunch program and the Women, Infants and Children (WIC) program come from California cows.
It may already be too late to rid California's cattle herds of the flu virus.
“It's on everyone's mind,” says Jack Hoekstra of the California Cattlemen's Association, an Oakdale dairy farmer. “The question is when and where and to what extent.”
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