In this 2023 photo, dairy cows graze in the Willamette Valley. Avian influenza has been found in dairy cows in several states, though so far, Oregon is not one of them.
Courtesy Jenifer Cruickshank
Federal and state regulators are working with officials in states where avian influenza has been found in dairy cows. So far, Oregon is not one of those states, but officials are taking precautions and coordinating with the U.S. Department of Agriculture, the Food and Drug Administration, and the Centers for Disease Control and Prevention, among others. Jenifer Cruickshank is an assistant professor and dairy extension specialist at Oregon State University in Corvallis. She joins us to tell us everything we need to know about bird flu in dairy cattle.
The following transcript was created by a computer and edited by a volunteer:
Dave Miller: This is Think Out Loud on OPB. I’m Dave Miller. Avian influenza is spreading through America’s dairies. Particles of the virus have been found in nearly 20% of milk samples nationwide. Outbreaks have been detected in 36 dairy herds in nine states. So far, Oregon is not one of those states but neighboring Idaho is, and Oregon officials are coordinating with the U.S. Department of Agriculture, the Food and Drug Administration and the CDC. Jenifer Cruickshank is an assistant professor and dairy extension specialist at Oregon State University. She joins us now with more details. Jenifer, welcome back.
Jenifer Cruickshank: Oh, thank you.
Miller: This is known as an avian virus, a bird virus because it originated in birds, but what effect does it have on cows?
Cruickshank: This is something that we only learned this last winter, where there’s been a spillover event at the very least in West Texas and herds there had cows that became sick. They went off their feed, their milk production dropped dramatically down to very low levels and the milk that they were giving was thicker and yellow, definitely not normal milk. Some of the cows showed fever, some of them had abnormal feces, either too loose or too firm. This prompted a veterinary investigation and that’s when it was identified as being avian influenza, the H5N1 strain that has been problematic when it’s jumped into poultry flocks the last few years.
Miller: And in those poultry flocks, it’s catastrophic, right?
Cruickshank: Yes, it’s very lethal. Fortunately, we don’t see that with cattle. Even those cows that show clinical signs and are quite ill do recover after two or three weeks. So, fortunately, it does not have the same effect in cattle.
Miller: You just outlined a whole series of things that I suppose dairy producers in Oregon, and all across the country, are on the lookout for right now?
Cruickshank: Yeah, I think that’s kind of how I would describe the mood, as being watchful. Probably paying a little bit more attention to biosecurity measures. In this case, that’s making your farm less welcoming to waterfowl because they seem to be the primary carriers of the disease.
Miller: How would you do that?
Cruickshank: Ideally, you don’t have ponds anywhere near where your cows are. Trying to make your farm as unattractive to water fowl as possible, so that they don’t want to stop there. Other biosecurity measures are our standard ones, where if you’re bringing any new animals onto the farm, they go into a quarantine area,where they don’t mix with the other animals for 30 days. Other kinds of basic ones include controlling who has access to the farm and using disinfectants.
Miller: Those biosecurity measures, are those always in place? Or are there specific things, either from USDA or from state authorities, that are specifically in place now because of this particular outbreak?
Cruickshank: What’s been enacted is there was a federal order from a few weeks ago, from USDA, requiring testing of cows that will be traveling between states. That applies to lactating dairy cattle only. In order to cross state lines, they need to have a negative test for H5N1 within seven days of making that move. There is an exception to that, though. If animals are moving directly to slaughter, which is where our retired dairy cattle go – they go on to their second career as beef providers – there’s an exception. If they are going to slaughter, there’s a USDA inspection process at slaughter facilities, so they don’t require the testing in those cases.
Miller: That is a brief career. I’m wondering if you can help me understand the two stats that I mentioned at the beginning, because I find them a little bit confusing put together. The first is that outbreaks have only been detected in 36 herds in the entire country, but the second is that federal officials have also detected the virus, or parts of the virus, in nearly one in five, 20%, of milk samples nationwide, after they looked at something like 1,000 samples, a pretty good selection. How do you make sense of both of those together?
Cruickshank: What I suspect we have … and this has been true on farms that have had identified infections, having clinical cows, cows that were sick, other cows on the farm have been fine. On those farms where they’ve had sick cows, it’s affected 10% or fewer of the herd, so you’ve got a lot of animals who aren’t showing any signs of illness at all. Probably what the case is, is that there are cows walking around who have subclinical cases, who by all appearances and measures are healthy, but maybe shedding virus. I’m speculating here, but there may have been additional spillover events to get us to that high level of detection of evidence of the virus in milk samples. That was certainly a surprising number, where 20% were coming back.
I do want to make the note that those tests were using PCR and identifying genetic material from the viruses, which can persist, not just of viruses but anything that does have nucleic acid. The nucleic acids can persist. The way that the test works is it’s just identifying certain pieces of the genetic material, so that doesn’t mean that there’s any functional virus in the milk supply.
Miller: It just means there are pieces of DNA that could still be identified in the cottage cheese, or the milk, or the half and half?
Cruickshank: Yes, and technically, influenza are RNA viruses.
Miller: Oh, RNA, I appreciate that. This is why we have the experts on; to correct us. In other words, you’re saying dairy consumers shouldn’t worry that particles of bird flu virus might be in the dairy that they’re buying at the store.
Cruickshank: No. Pasteurization is highly effective at disabling influenza viruses, and the FDA has confirmed that again, very specifically, with this new disease in cattle. I’ll point out that all food that we eat is gonna have trace nucleic acids, genetic material, from all kinds of things. That’s not unusual for milk.
Miller: What about raw milk for folks? A much, much smaller number of consumers, who are maybe buying unpasteurized milk directly from a farm, say. Is there more concern there?
Cruickshank: There definitely is. Pasteurization is very effective at disabling the virus, and raw milk, of course, is not going through that pasteurization process. So, were that milk to contain H5N1 viruses or any other pathogens for that matter, then that could be consumed by the person who drinks it. There’s definitely a much higher risk with raw milk consumption.
Miller: So far, there’s only been a report of one person, a dairy worker, who contracted this virus from a cow. That worker, I’ve read, had a minor eye infection that apparently cleared up after a couple of days, but are there still scarier spillover scenarios, where the virus jumps from livestock to people and morphs in a way that makes it a lot more dangerous?
Cruickshank: Yeah, for sure. There is definitely that concern. This comes back to the watchfulness on the part of federal and state agencies, and dairy farm owners, and veterinarians. That watchfulness, of keeping an eye on it, [is important] because that is a concern, that the virus will undergo a mutation that makes it easier to jump into humans or enables the virus to become more virulent. We can transfer a lot of the concerns that we have about COVID, which is also a virus, over to this scenario; this could happen and hopefully it won’t, but we’ll keep an eye on it.
Miller: Jenifer, thanks very much.
Cruickshank: Oh, you’re very welcome. Thanks for having me.
Miller: Jenifer Cruickshank is an assistant professor and dairy extension specialist at Oregon State University.
Contact “Think Out Loud®”
If you’d like to comment on any of the topics in this show or suggest a topic of your own, please get in touch with us on Facebook, send an email to thinkoutloud@opb.org, or you can leave a voicemail for us at 503-293-1983. The call-in phone number during the noon hour is 888-665-5865.