As California struggles to contain a growing number of H5N1 bird flu outbreaks on Central Valley dairy farms, veterinary experts and industry observers are expressing concern that the number of cattle deaths is far higher than foreseen.
Although dairy farmers have been told to expect a mortality rate of less than 2 percent, preliminary reports suggest that 10 to 15 percent of infected cattle die, according to veterinarians and dairy producers.
“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 just like, wow. On the production side, it’s much more serious than we had hoped. And in terms of health, it’s much more serious than we were led to believe.”
A total of 56 California dairy farms have reported bird flu outbreaks. At the same time, public health officials reported two suspected cases of H5N1 infections among dairy workers in Tulare County, the nation’s largest dairy-producing county. With more than 600,000 dairy cows, the county represents approximately 30% of the state’s milk production.
Beal’s observations were confirmed by others during a Sept. 26 webinar for dairy producers, hosted by the California Dairy Quality Assurance Program, an arm of the industry-funded California Dairy Research Foundation. A summary of the results and the sightings were reported in a newsletter released earlier this week by the program.
Beal, along with Murray Minnema, another Central Valley veterinarian, and Jason Lombard, a Colorado State University veterinarian, described their observations and data to dairy farmers to help them anticipate signs and symptoms. treatments for the virus.
The webcast was not made available to The Times.
“The animals are really not doing well,” Beal told the Times.
He said the infected cows he’s seen are no different from people suffering from a typical flu: “They don’t look so sexy.” »
He and others think recent heat could be a factor.
Since late August, the Central Valley has suffered multiple heat waves, with daytime temperatures exceeding 100 degrees.
“Heat stress is still a problem in dairy cattle here in California,” he said. “So you take that, you add this virus, which still has a certain affinity for the respiratory tract… we always see a little snotty nose and heavy breathing in animals that are affected… and for some d Between them, it’s just stress that gets the best of them.
Indeed, most deaths are not directly a result of the virus, he said, but are “virus-adjacent.” For example, he observed many bacterial pneumonias, likely the result of a cow’s suppressed immune system, as well as bloat.
He said when cows aren’t feeling well, they often don’t eat.
“The digestive tract, or rumen, essentially requires movement. You have to have things constantly coming out of that rumen to keep the pH balance and the microbiome where it should be,” he said. So when they don’t eat, things get stagnant in the digestive tract.
This causes them to “suffocate because their diaphragm is putting too much pressure on it.”
Additionally, he and others see wide variations in disease duration.
Although early reports suggest the virus appears mild and only lasts about a week or two, others see it lasting several weeks. According to the industry newsletter, at one dairy, cows were shedding the virus 14 days before showing clinical signs of illness. It then took three more weeks for the cows to get rid of the virus.
They also note that the virus affects a larger percentage of herds – in some cases, 50 to 60% of the animals. This is much more than the 10% previously announced.
Some say the real rate could be even higher.
“I suspect the infection is even higher; 50 (% to) 60% show clinical signs due to heat stress or better monitoring of the herd earlier in the infection. Unfortunately, few if any herds have been retrospectively evaluated by serological testing to determine true infection rates,” said John Korslund, a retired veterinary epidemiologist with the U.S. Department of Agriculture.
Cows also don’t return to 100% production after clearing the virus, Beal said. Instead, he and others say the figure is closer to 60 to 70 percent.
“Some animals will be removed from the herd because they never seem to come back,” he said.
Beal said his direct observations challenged his ideas about the disease, which has so often been portrayed as benign and insignificant.
“Once I saw it myself, I said this is something I need to communicate with my clients about. … This is not just a table joke,” he said. “I didn’t want people to not take this seriously, because I see what it does to animals, and it’s hard to see – as an animal caretaker, as a veterinarian like me – what is just not something pleasant. It’s more serious than we were led to believe.
Beal said he works hard with Central Valley farmers to care for animals, largely by making sure livestock are properly hydrated. He also treats sick cows with a medicine similar to aspirin to reduce fever, pain and discomfort.
He said the treatment is quite effective and seems to be helping.
Others aren’t surprised that H5N1 is becoming more serious in cows.
“As I have said since we learned of the outbreak in dairy cows, nothing we have learned about this virus is new or unexpected,” said Rick Bright, a virologist and former director of the US Biomedical Advanced Research and Development Authority. “He behaves exactly as we have known him to for the last 25 years. It’s now spreading very efficiently among mammals, and it’s mutating and adapting to mammals as it goes.
He thanked state health officials and veterinarians for “being more open and transparent with their data” than other states, and said that could be why the virus appears to be hitting so hard Californian cows.
“This virus is out of control. It is time for urgent and serious leadership and action to stop transmission and mutations,” Bright said. “The idea of letting it burn through food animals, with unmonitored voluntary testing, has failed. There are pandemic strategies that we need to dust off and start implementing.
Meanwhile, authorities continue to reassure the public about the security of the country’s dairy supply. Pasteurization is said to inactivate the virus. They also warn people not to consume raw milk.
Beal noted that one of the sentinel signs that a farm has been infected is the death of barn cats who drank infected raw milk.
“It’s strange, actually, how everywhere this seems to be happening,” he said. “It’s quite sad and shocking. But sometimes it’s one of the first things people see.
It also appears that some cows recovered from the virus have been reinfected, although this has not been confirmed.
“We don’t have data yet to support this, but there have been anecdotal reports of reinfections in flocks,” said Kay Russo, a dairy poultry veterinarian at RSM Consulting, an international company.
She said it could just be an observed persistent infection, but also speculated that the virus could mutate quickly – and evolve “enough to re-infect an animal.”
And Jason Lombard, one of the speakers at the dairy webinar, said in an email that veterinarians have told him they are seeing clinical signs of disease in infected animals, “but I don’t think that ‘none of them were infected.’ been confirmed by tests.
As of October 4, California authorities had reported 56 infected herds. Although state officials do not disclose the locations of these herds, the website Valley Veterinarians Inc. – a veterinary clinic run by large animal veterinarians in the Central Valley – said the infections were in the Tulare and Fresno counties.
Steve Lyle, a spokesman for the California Department of Food and Agriculture, would not confirm the counties.
There are more than 200 herds in Tulare County and more than 100 in Fresno County. The state’s largest raw milk dairy is also in Fresno County.
Requests by The Times to observe infected farms or speak with owners of infected dairies went unanswered by the state and were denied by industry insiders.
“We don’t recommend that farmers go down this route because of the farm safety issues we’ve had,” said Anja Raudabaugh, executive director of Western United Dairies, a trade group for California dairy farmers. “It is very unwise to consider visiting a quarantined dairy. … It’s just not the time.”
She said her organization doesn’t want anyone to “dox” farmers or increase traffic on or near a farm, “which has happened in both cases.”
Last week, the H5N1 virus was detected in wastewater samples collected in Turlock, San Francisco, Sunnyvale and Palo Alto.
State Epidemiologist Erica Pan said it’s difficult to know where the virus is coming from. Although Turlock is a dairy hub, detections in San Francisco Bay Area cities could potentially come from wild birds, she said, but the source is unknown.