Bird flu spreads to California's dairy cows

A type of bird flu that is extremely fatal to birds has been confirmed in dairy cows in California, the state Department of Food and Agriculture announced Friday afternoon.

No human cases have been confirmed to date and the virus, a flu subtype called H5N1, will not be considered a big public health threat, in response to state health officials. At this time, there are not any concerns concerning the safety of the business milk or food supply, they said.

But doctors are monitoring farm staff who can have had contact with infected animals to make sure rapid isolation and care in the event that they change into ailing, the California Department of Public Health said. Authorities said they might officially confirm all cases related to this outbreak.

This is the primary time that cows infected with the virus have been identified within the state. California is the 14th state within the US to report H5N1 infection in dairy cows.

The animals within the Central Valley began showing signs of illness on Sunday, CDFA reported. The test results were confirmed by the national veterinary laboratory on Friday. The herds have been quarantined.

“We have been preparing for this possibility since earlier this year when … discoveries were confirmed on dairy farms in other states,” said CDFA Secretary Karen Ross. “Our extensive experience with poultry has given us sufficient preparation and expertise to manage this incident, with worker health and public health as our top priorities.”

Other states have reported 4 cases amongst dairy staff since April 2024: one each in Texas and Colorado and two in Michigan. All 4 of those individuals have recovered, and there are not any reports of further spread amongst people around them.

Until recently, California's dairy farms appeared to have been spared from the crisis. The state's 1.7 million dairy cows provide about 20 percent of the country's milk.

“These are tough times for our dairy farmers given the economic challenges they face in a dynamic market,” Ross said. “So I want to assure them that we are addressing this incident with the utmost urgency.”

Experts say it’s crucial to get more details about how people became infected and whether the virus has evolved to contaminate people more easily.

There isn’t any state or federal requirement to routinely sample cows or milk. Clinical signs of flu occur in just a fraction of cases, so some experts fear the virus could possibly be hiding in untested animals.

State health officials recommend that farmworkers and emergency responders wear personal protective equipment (PPE) – masks, gloves, caps, face shields and safety glasses – when working with animals or potentially infected materials.

“I've been concerned about this for months,” Krutika Kuppalli, medical officer for COVID-19 health operations on the World Health Organization, said in a social media post. “That's why we need increased monitoring and transparency of testing protocols.”

Over the past three years, the deadly and highly contagious virus has circulated the globe, causing horrific losses amongst birds in over 80 countries.

After emerging in 2020, the virus sparked major outbreaks in Europe, Africa and Asia. In January 2022, it reached the United States and spread to the country's largest poultry farms within the East and Midwest, driving up egg prices.

The virus is now so widespread in wild birds that it has repeatedly jumped to mammals, particularly species similar to foxes that feed on infected birds.

Signs of the H5N1 bird flu virus have been detected at wastewater treatment plants in San Francisco, Palo Alto and the West County Wastewater Plant in Richmond, amongst others.

However, it’s believed that the disease originates from the droppings of untamed birds within the sewage system, which collects and treats wastewater and rainwater.

The virus has already been detected in wild birds and domestic poultry within the state. Last winter, it spread within the historic poultry region of Sonoma County, resulting in the killing of 1.1 million birds.

The source of the brand new cattle infections is unknown. The federal government requires that dairy cows be tested for the virus before they may be transported across state borders.

“The main vector of the virus is waterfowl – ducks and geese, which like the lush habitat of California,” says veterinarian Maurice Pitesky of the UC Davis School of Veterinary Medicine. Pitesky studies the spread of bird diseases.

For probably the most current information on avian influenza in livestock in California, visit the Department of Food and Agriculture website at www.cdfa.ca.gov/AHFSS.

Originally published:

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