Less than a week after California health officials confirmed the discovery of the bird flu virus in store-bought raw milk, state agriculture officials descended on Mark McAfee’s Raw Milk Dairy on Wednesday and began collecting samples from the farm’s two herds, creamery, bulk milk tanks and trucks, according to the owner.
The visit follows a recall of raw milk products, and comes amid a growing series of H5N1 bird flu outbreaks on government dairy farms. Raw Farm houses 1,800 cattle spread over two herds — one in Fresno, the other outside Hanford, according to McAfee. The company also owns a Fowler-based creamery.
“I think they are in full attack mode,” he said, describing the search as thorough. In addition to milk, Raw Farm produces cheese and kefir.
As California Department of Food and Agriculture officials collected samples and performed tests on the milk Wednesday, some health experts raised questions and concerns about the recent positive test results.
Last week, public health officials in Santa Clara County detected the bird flu virus in a sample purchased from a McAfee’s green milk store. Two days later, the California Department of Public Health confirmed the findings.
But when agriculture officials tested the cows at McAfee’s dairy farm on Monday, they failed to identify the virus.
The fact that not a single animal has been reported to be infected has puzzled and worried public health experts. Often, once a virus appears on a farm, it spreads and does not simply disappear.
“The fact that all the additional tests are wrong really worries me,” John Korslund, a retired US Department of Agriculture epidemiologist, said in an email.
CDFA officials could not be reached for comment Wednesday, but infectious disease experts told The Times that officials may be reviewing testing procedures, as well as the actual origin of the sampled milk.
According to testing records, the first sample of raw milk bought at the store had high levels of the virus, and was found to have a polymerase chain reaction threshold – or Ct – cycle of about 25.
“The herd should not go bad immediately after the 25th reading if it is indeed milk from the same herd, IMO,” Korslund wrote in an email.
Richard Webby, director of the World Health Organization’s Collaborating Center for Studies on the Ecology of Influenza in Animals and Birds, and a researcher in the Department of Infectious Diseases at the Children’s Research Hospital of St. Jude in Memphis, Tenn., agreed.
“OK, that’s not a weakness… and it’s definitely not on the borderline where some tests will have it and others won’t,” he said after reviewing the test records.
Webby, Korslund and other experts say that the test used only looks at the H5 part of the H5N1 virus, and will not determine whether the virus is inactive, or alive. A second test – called a virus isolation test – must be done to confirm that the sample is H5N1 and that it is active.
Federal and state health officials say the H5N1 bird flu virus poses little risk to the public. However, they urged people not to drink raw, unpasteurized milk. There have been no reported outbreaks in consumers associated with bird flu from infected raw milk.
The milk was bottled on Nov. 9. Raw Farm LLC recalled all products related to the good sample. McAfee estimated that the recall involved about 2,000 gallons of half-and-a-half whole milk products.
Since the outbreak began, 461 cattle have been infected in California – including herds in Fresno and Kings County, where McAfee’s herds are located.
At the beginning of the H5N1 milk outbreak, state health officials tested samples of contaminated milk and found the virus in 20% of the samples collected from retail shelves. However, when further tests were carried out – isolation of the virus – they were able to show that it was an inactive virus that had been heat-treated.
So, why then does a sample of raw milk test positive for the virus and the dairy herd does not?
Korslund acknowledged that testing and sampling can sometimes be risky, but he was not inclined to question testing this time. He said the Ct value — and the lack of subsequent testing — raises “an issue of product integrity rather than herd infection.”
“What if at some point in the bottling process, shelf-stable milk that has been skimmed is added to raw milk to meet shortages? In such a case, we do not have an evaluation problem; rather it is an issue of product integrity that usually cannot be seen,” he said.
That’s why testing for virus isolation is important, Korslund said. It can help determine whether the virus in the collected sample is alive or not.
A spokesman for the National Department of Health said that the sample testing has been completed. He did not say whether the isolation of the virus has been completed, but noted that a positive result has been confirmed by both state laboratories and now laboratories.
McAfee said he does not think the virus is present in his herd. The tests carried out by the government’s agriculture department regularly – twice a week – on most of his milk were absent. In addition, he noted, the test taken on Monday also did not show the virus.
In addition, he said, he monitors each cow on his farms with a high-tech device – made by the Austrian company smaXtec – that sits on the cow’s udder and sends real-time information about the animal’s body temperature, milk acidity, etc.
He said there are no indications that the virus is circulating in his herd based on that data.
He also said that all his equipment – from his trucks, to his many tanks and bottling plant – is closed except for farms and dairy; are used exclusively by Raw Farm, LLC.
He said he is concerned that state officials are determined to “find something.”
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