Bird flu continues to have a significant impact on California’s animal ag industry, with 755 of their dairies and millions of birds affected since the first detection.
Poultry cases have also been detected in multiple states, including Pennsylvania, within the last 30 days, while dairy cases have been detected in Nevada and Idaho, in addition to California.
In the past month, around a dozen commercial poultry facilities in Pennsylvania have tested positive for HPAI.
Dr. Alex Hamberg, Pennsylvania State Veterinarian, Director of the Bureau of Animal Health and Diagnostic Services and Executive Director of the Animal Health and Diagnostic Commission, said in a webinar last week that the state remains only the third to maintain Stage 4, known as ongoing absence of the virus from its dairy herd. Pennsylvania is also the only state with over 100 herds to achieve that, he added.
“That’s a pretty big milestone and that shows that statistically speaking, we can say with confidence, there is no HPAI in Pennsylvania’s dairy cows,” Hamberg said.
Nationally, in the last 30 days, there’s been detections in California, Nevada, and Idaho, with the B3.13 genotype still circulating heavily in California and Idaho. “That’s the particular strain that caused havoc in California as well as Colorado and several other states and is also the one that has such a propensity to go between cattle and poultry and then back to cattle and spread laterally,” Hamberg said.
The cases that have been in Nevada and Arizona to a large extent, as well as a few in California, that have largely been the D1.1 cases, he added. D1.1 is the predominant strain in wild birds on all of the flyways in the US right now. It does appear that these are all direct spillover events.
“There isn’t direct evidence at this point of lateral spread, meaning we don’t have evidence to show that it’s spreading from farm to dairy farm to dairy farm, but it seems to be going from wild birds to dairy farms,” he said.
Clinically, the strain seems affect cows less, but ‘there’s still a lot to be learned, he warned. “The clinical illnesses seem to be fewer than what we saw with the B3.13, but this is still very much a developing situation that we need to keep a close eye on.”
Studies on raw cheese & milk
Hamberg moved to dispel fears that the ageing of raw cheese may not be enough to eradicate the live virus from the food product.
The findings were made as part of a study, where researchers spiked milk with viable H5N1 virus and then put it through 60-day cheese-making and aging process to find out if any viable virus survived at the end of the period.
Cheese maturation: How long is enough?
According to the Food and Drug Administration, cheese made from unpasteurized milk must be aged at not less than 35ºF (around 1.7ºC) for at least 60 days. After 60 days, it is considered that the acids and salts in raw milk cheese naturally minimize the risk of pathogens from growing.
“They found that cheeses that were aged at a pH of between 5.8 and 6.6 still had a viable virus after 60 days,” Hamberg explained. “Those with a pH of 5 or less, the virus did not survive the cheese-making process.”
“What we’ve got here is a single study that is in preprint, which means I can only see the abstract of it,” he explained. “I haven’t seen the materials and methods and all the rest of the data so we’re probably going to need a little bit more information to put that finding in context and figure out what does that mean for a consumer standpoint or a public health standpoint.”
He also discussed a national study that is currently surveying raw milk cheeses for the H5N1 virus. “They collected over 100 samples [from commercial channels] so far out of the 300 intended. Of those, they’ve tested just shy of 100 and have not found any virus at all in these off-the-shelf cheeses [and] there’s still another 200 samples to go so it remains to be seen what they will find. Not finding any in roughly one third of the samples they tested already [is] a pretty good indicator, but we still got two thirds left to test.”
“I wouldn’t put too much weight into these studies yet,” Hamberg concluded.
Biosecurity ‘still very important’
Hamberg warned that farmers must not become complacent – particularly in states like Pennsylvania where the virus is still not detected.
“Biosecurity, it’s still very important, especially with the fact that now we’re starting to see D1.1 come in as well as the fact that B3.13 is still out there and it’s still causing problems, specifically in California and Idaho but it could potentially crop up elsewhere,” he said.
“Biosecurity on a dairy farm looks very different from biosecurity on a poultry farm or a pig farm because they are different species with different needs.”