As California struggles to contain a growing number of H5N1 bird flu outbreaks on Central Valley dairy farms, veterinary experts and industry observers are raising concerns that the number of cattle deaths is much higher than anticipated.
Although dairy operators were told to expect a mortality rate of less than 2%, preliminary reports suggest that 10% to 15% of infected cattle are dying, according to veterinarians and dairy farmers.
“I was shocked when I first encountered it in my herd,” said Maxwell Beal, a Central Valley-based veterinarian who has been treating infected herds in California since late August. “It was just like, wow. From a production standpoint, it’s more serious than we expected. And from a health perspective, it’s more serious than we thought.”
A total of 56 dairy farms in California have reported outbreaks of bird flu. At the same time, state health officials Two suspected cases have been reported Spread of H5N1 infection among dairy workers in Tulare County, the largest dairy-producing county in the country. With more than 600,000 dairy cows, the county It accounts for about 30% of the state’s milk production.,
Beal’s comments were confirmed by others during a webinar for dairy farmers on Sept. 26, hosted by the California Dairy Quality Assurance Program — a branch of the industry-funded California Dairy Research Foundation. Summary of Findings And the comments were reported by the program in a newsletter published earlier this week.
Beal, along with another Central Valley veterinarian, Murray Minnema, and Colorado State University veterinarian Jason Lombard, described their observations and data to dairy farmers to help them predict symptoms and treatments for the virus.
The webcast was not made available to The Times.
“The animals don’t really fare well,” Beal told The Times.
He said the infected cows he has seen are no different from those suffering from normal flu: “They don’t look so hot.”
He and others believe recent heat may be a cause.
Since late August, the Central Valley has suffered several heat waves, with daytime temperatures exceeding 100 degrees.
“Heat stress is always a problem for dairy cattle in California,” he said. “So you take that, you add in this virus, which has some similarity to the respiratory tract… We always see a little runny nose and heavy breathing in affected animals… and some of them For, just the stress takes them.”
In fact, he said, most deaths are not directly the result of the virus but are “associated with the virus.” For example, she has seen a lot of bacterial pneumonia, which is likely a result of the cow’s weak immune system as well as inflammation.
He said that when cows are not well, they often do not eat anything.
“The digestive tract, or rumen, fundamentally needs movement. “Things have to be constantly moving out of the rumen for the pH balance and microbiome to be where they need to be,” he said. Therefore, when they are not eating food, things stagnate in the digestive system.
In turn, this causes them to suffocate because there is too much pressure on their diaphragm.
Additionally, they and others are also seeing significant differences in the duration of the disease.
While initial reports suggested the virus seems to be mild and only last a week or two, others are seeing it lasting several weeks. At one dairy, cows were shedding the virus 14 days before they showed clinical signs of illness, according to an industry newspaper. After this, it took three more weeks for the cows to get rid of the virus.
They are also seeing that the virus is affecting larger percentages of the herd – in some cases 50%-60% of the animals. This is much higher than the previously reported 10%.
Some say the actual rate may be even higher.
“I would guess that the infection is even higher; 50–60% are showing clinical signs due to better herd surveillance at the onset of heat stress or infection. Unfortunately, few or no herds have been retrospectively evaluated through serology testing to determine actual infection rates,” said John Korslund, a retired U.S. Department of Agriculture veterinary epidemiologist.
Cows also are not returning to 100% production after being cleared of the virus, Beal said. Instead, he and others say it is closer to 60%-70%.
“There will be some animals that will be removed from the herd because they will never come back,” he said.
Beal said her first-hand observations have actually challenged her assumptions about the disease, which has often been dismissed as mild and unimportant.
“Once I saw it myself, I said, this is something I need to communicate with my customers about… this isn’t something that’s just a joke at the dinner table,” he said. Said. “I didn’t want people to not take it seriously, because I see what it’s doing to animals, and it’s hard to see — as an animal carer, as a veterinarian like me — this is something Not something that’s enjoyable. “This is much more serious than we were led to believe.”
He said he’s working hard with Central Valley farmers to treat animals better — mainly by making sure cattle are adequately hydrated. He also treats sick cows with medicines like aspirin to reduce fever, pain and discomfort.
He said that the treatment is quite effective and seems to be helping.
Others aren’t surprised that H5N1 is becoming more serious in cows.
Rick Bright, a virologist and former head of the US Biomedical Advanced Research and Development Authority, said, “As I’ve said, since we first learned about the outbreak in dairy cows, we’ve learned everything we can about this virus. What is learned is not new or unexpected.” “It is behaving exactly as we have known about this virus over the last 25 years. It is now spreading very efficiently among mammals, and it is mutating and adapting to the mammals.
He credited state health officials and veterinarians for “being more candid and transparent with their data” than other states, and said that’s why the virus is affecting California’s cows so badly.
“This virus is out of control. It is time for urgent and serious leadership and action to prevent further transmission and mutation,” Bright said. “With uncontrolled voluntary testing, the concept of letting it burn through food animals has failed. There are pandemic playbooks that we need to dust off and start implementing.
Meanwhile, officials continue to reassure the public about the security of the country’s dairy supply. They say that pasteurization inactivates the virus. They also warn people to stay away from raw milk.
Beal noticed that one of the sentinel signs that a farm was infected were dead barn cats that had drank infected, raw milk.
“It’s really strange that this keeps happening everywhere,” he said. “It is very sad and shocking. But it’s one of the first things people see sometimes.”
There is also some suggestion that some cows who have recovered from the virus have been reinfected, although this has not been confirmed.
“We don’t have any data to support it yet, but there have been anecdotal reports of reinfection in herds,” said Kay Rousseau, a dairy-poultry veterinarian at international consulting firm RSM Consulting.
He said it may just be a persistent infection that is being observed, but also speculated that the virus could mutate rapidly – and evolve “enough to re-infect an animal.”
And Jason Lombard, one of the speakers at the dairy webinar, said in an email that he was told by veterinarians that they are seeing clinical signs of the disease in infected animals, “but I do not believe that any of them “This has never been confirmed through testing.”
As of October 4, California officials have reported 56 infected herds. Although state officials will not disclose the location of these herds, Valley Veterinarians Inc. The website — a veterinary clinic run by large animal veterinarians in the Central Valley — said the infections are in Tulare and Fresno counties.
California Department of Food and Agriculture spokesman Steve Lyle 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 inspect infected farms or speak to owners of infected dairies went unanswered by the state and were declined by industry insiders.
“We are not advising farmers to get involved because of the farm safety issues we have,” said Anja Raudabaugh, chief executive of Western United Dairies, an industry trade group for California dairy farmers. “It is very unwise to consider looking at any dairy under quarantine…this is not the right time.”
He said his organization doesn’t want anyone to “dock” farmers or increase traffic on or near a farm, “both of which have happened.”
In the past week, the H5N1 virus has been detected in wastewater samples collected in Turlock, San Francisco, Sunnyvale and Palo Alto.
State epidemiologist Erica Pan said it is difficult to know where the virus is coming from. While Turlock is a dairy center, Bay Area cities could potentially be affected by wild birds, he said, but the source is not known.
