As California struggles to contain a growing number of H5N1 bird flu outbreaks on Central Valley dairy farms, animal experts and industry observers are expressing concern that the number of cattle deaths is higher than expected.
Although dairy producers have been told to expect a mortality rate of less than 2%, initial reports indicate that between 10% and 15% of infected cows die, according to veterinarians and dairy farmers.
“I was shocked the first time I encountered it in one of my herds,” said Maxwell Beal, a Central Valley-based veterinarian who has been treating infected herds in California since late August. “It was like, wow. Production-wise, this is worse than we hoped. And health-wise, it’s worse than we’ve been led to believe. “
56 California dairy farms have reported bird flu outbreaks. At the same time, state health officials reported two cases of suspected H5N1 infection among dairy workers in Tulare County, the nation’s largest dairy county. With over 600,000 dairy cows, the region accounts for about 30% of the state’s milk production.
Beal’s observations were confirmed by others during a Sept. 26 webinar for dairy farmers hosted by the California Dairy Quality Assurance Program – the industry-funded arm of the California Dairy Research Foundation. A summary of the findings and observations was reported in a newspaper published earlier this week by the program.
Beal, along with Murray Minnema, another veterinarian in the Central Valley, and Jason Lombard, a veterinarian at Colorado State University, explained their observations and information to dairy farmers to help them anticipate symptoms and treatment of the virus.
The webcast was not made available to The Times.
“Animals don’t really do well,” Beal told The Times.
He said the infected cows he saw were not like people suffering from the common cold: “They don’t look very hot.”
He and others think the recent heat may be the cause.
Since the end of August, the Central Valley has suffered from numerous heat waves, with daytime temperatures exceeding 100 degrees.
“Heat stress is always a problem for dairy cows here in California,” he said. “So you take that, you add this virus, which has some relevance to the respiratory system … we always see stuffy noses and heavy breathing in animals that are affected … and in some of them, it’s just the stress that takes them over.”
Of course, most of the deaths are not the result of the virus, he said, but “the virus is nearby.” For example, he has seen pneumonia caused by many bacteria, which may be the result of a suppressed immune system of the cow, and constipation.
He said that if the cows are not well, they often do not eat.
“The digestive tract, or rumen, basically needs to move. There has to be something coming out of that rumen constantly so that the pH and microbiome balance stays where it should be,” he said. So, when they don’t eat, things in the digestive tract stop.
That then makes them “out of breath because their diaphragm has too much pressure.”
In addition, he and others see significant differences in the duration of illness.
While early reports suggested that the virus appeared to be mild and lasted about a week or two, others saw it a few weeks ago. According to the industry newspaper, in one building, cows shed the virus 14 days before showing signs of illness. It then took another three weeks for the cows to clear the virus.
They also see that the virus affects a large percentage of herds – in some cases 50%-60% of the animals. This is significantly higher than the 10% previously reported.
Some say the actual rate may be even higher.
“I would think that the infection rate is very high; 50-60% show clinical signs due to heat stress or better monitoring of the herd early in the infection. “Unfortunately, few or no herds have been retrospectively tested with serology to determine true levels of infection,” said John Korslund, a retired US Department of Agriculture epidemiologist.
Cattle also do not return to 100% production after clearing the virus, Beal said. Instead, he and others say it’s closer to 60%-70%.
“There will be animals that are taken out of the herd, because they don’t seem to be coming back,” he said.
Beal said his first-hand experience really challenged his views on the disease, which is often described as mild and innocuous.
“When I see it for myself, this is something that I have to communicate with my customers about … it’s not just something to play on the table,” he said. “I didn’t want people to take it too seriously because I see what it does to animals, and it’s sad to see – as someone who takes care of animals, as a vet like me – it’s not just a happy thing. It is more serious than we have been led to believe.”
He said he works hard with farmers in the Central Valley to treat livestock – especially making sure the cows have enough water. He also treats sick cows with aspirin-like medicine, to reduce fever, pain and discomfort.
He said the treatment is working well, and seems to be helping.
Some are not surprised that H5N1 is becoming more severe in cattle.
“As I have said since we first heard about the outbreak in dairy cows, we have learned nothing about this virus that was new or expected,” said Rick Bright, an infectious disease doctor and former head of the US Biomedical Advanced Research and Development Authority. “It behaves as we have known this virus for the past 25 years. It’s spreading very well now among mammals, and it’s evolving and adapting to mammals as it does.”
He thanked the government health officials and the veterinarian for “coming and making their information public” than other states, and said this could be the reason why the virus seems to be hitting California’s cattle so hard.
“This virus has gotten out of control. It is time for urgent and strong leadership and action to stop the transfer of reforms,” said Bright. “The idea of letting it burn with predators, with unsupervised voluntary testing, has failed. There are epidemic playbooks that we need to get rid of and start using.”
In the meantime, officials continue to reassure the public about the safety of the nation’s dairy product. They say that pasteurization activates the virus. They also warn people to stay away from raw milk.
Beal noted one of the signs that the farm was infected were dead cats that drank infected milk.
“It’s strange, actually, how that seems to happen everywhere,” he said. “It’s sad and shocking. But that’s one of the first things people notice sometimes.”
There is also a suggestion that some cows that have recovered from the virus have become infected again, although this has not been confirmed.
“We don’t have data to support this yet, but there have been unexplained reports of reinfection in herds,” said Kay Russo, a dairy veterinarian with RSM Consulting, an international consulting firm.
He said it may be a persistent infection that is seen, but he also pointed out that the virus can mutate quickly — and mutate “enough to re-infect an animal.”
And Jason Lombard, one of the speakers at the milk webinar, said in an email that he was told by veterinarians that they see signs of disease in infected animals, “but I don’t believe they have any.” verified by testing.”
As of October 4, California officials have reported 56 infected flocks. Although government officials would not disclose the location of the herds, the website of Valley Veterinarians Inc. – an animal clinic operated by large veterinarians in the Central Valley – said diseases in Tulare and Fresno counties.
Steve Lyle, a spokesman for the California Department of Food and Agriculture, would not confirm the districts.
There are over 200 herds in Tulare County and over 100 in Fresno County. The largest dairy in the state is also located in Fresno County.
Requests by The Times to see infected farms or to speak to affected dairy owners were not answered by the government and were denied by industry insiders.
“We’re not recommending farmers participate in this because of the farm safety issues we’ve had,” said Anja Raudabaugh, chief executive officer of Western United Dairies, a trade group for California’s dairy farmers industry. “It’s not very wise to think about watching the dairy in isolation … now is not the time.”
He said that his organization does not want anyone who “runs tricks” on farmers or increases traffic on the farm or near the farm, “both have happened.”
In the past week, the H5N1 virus has been detected in wastewater samples collected in Turlock, San Francisco, Sunnyvale and Palo Alto.
Epidemiologist Erica Pan said it is difficult to know where the virus is coming from. Although Turlock is a dairy center, the songs played in Bay Area towns may have come from wild birds, he said, but the source is unknown.
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