What is the status of the H5N1 outbreak in dairy within Michigan as of June 2024?
Pam Ruegg: Yeah, so we are unfortunately the state that has the most effective herds, at least that have been confirmed in Michigan. We have 25 confirmed herds. That means these herds have submitted samples from at least one cow for polymerase chain reaction (PCR) testing at a certified veterinary diagnostic lab. And of those 25 herds, they're distributed in 10 counties. The 10 counties are clustered together in the middle and west of our state. They're not randomly distributed. We also have had 6.5 million chickens and poultry that have been sacrificed and those birds are located in the same approximate counties as the cattle.
The animals in the herd were detected a couple of months ago. The first animal, the first herd was affected directly by shipment of an affected animal from Texas. This was an animal that came from the Texas-affected herds, which were the first herds affected. It was clinically normal in the herd when it arrived and then it spread to the rest of the herd, and that was our kind of sentinel herd in the state.
How long is H5N1 stable in milk and is pasteurization effective at inactivating the virus?
Nicole Martin: There have been a few groups who have looked at the stability of this particular strain in raw milk at various temperatures, and it does appear to be quite stable. I've seen data from a couple of groups and it appears to still be infectious at weeks after the sample was taken. So extremely stable at refrigeration temperatures. So, 4°C at higher temperatures, it declines more rapidly. But obviously, the fact that it is fairly at low temperatures is concerning because those are the temperatures that we maintain milk at in the supply chain for the dairy industry.
Again, a couple of studies have come out both with this specific strain as well as similar strains that are not infecting cattle right now on the efficacy of pasteurization, both high-temperature, short-time pasteurization, which as you know is the most common type of pasteurization that we use in the United States for fluid milk as well as batch or vat pasteurization, which is 63°C for 30 minutes. And we do see fairly large declines in infectious dose after pasteurization at both temperatures.
Studies are varying though on what that log reduction is in the viral load. I've seen five log up to about six-and-a-half log. And those of us who are sort of looking at the literature on H5N1 inactivation and egg pasteurization, frankly, we're expecting a higher reduction simply because of the compositional differences in eggs versus fluid milk. And so, the things that we're looking at though are obviously the initial dose or viral load of the milk is very high. So that's one factor.
And then also I mentioned the compositional differences. So, we know in the milk from clinically affected cows, the composition of that milk is quite different. Usually, I don't know, Pam might know better than I do if anybody has actually measured the composition of that milk or not. But that also affects heat transfer, right? So, when you have higher total solid content that reduces your heat transfer effectiveness, and so that can impact the overall heat treatment effectiveness for viral inactivation.
Might federal or state governments require testing on dairies in the future?
Pam Ruegg: I have no way to answer that—whether or not there'd be federal regulation or state regulation. Right now there are no regulations relative to testing. If you do test, it is a reportable disease. There are herds that are not testing because they already know what the clinical signs look like. But right now, that's a really hot political topic and I think that it would be a big step to mandate required testing at this time and it'd be hard to enforce.
[Update: Colorado has issued a new mandate, effective July 22, 2024, requiring all licensed dairy farms in the state to submit weekly bulk-tank samples for testing. The order is meant to identify and isolate instances of Highly Pathogenic Avian Influenza (HPAI) and prevent further spread of the virus in the state’s dairy and poultry farms.]
Should bulk tank testing be made mandatory?
Pam Ruegg: I'm not even going to attempt to answer that as it is a really, really hot political item. I think there's great concerns that we maintain the integrity and the trust of the consumers in the milk so far.
And Nicole knows more about this than I do, so far we feel like we are with what we're seeing. I would say I just saw a very, very recent study, they did a mathematical calculation on how many herds would have to be affected to actually impact productivity and stuff in the US and it would be an enormous number of herds. So, I think the thing that we really want to look at is stopping the spread of this disease.
I personally think that some of the movement restrictions have been at least somewhat effective in doing that because the spread between states has been less fast than many of us have expected.
Is milk the only product of dairy production that we should be concerned about? Are there any concerns with semen, embryos, or other methods for transmitting this virus, such as mechanical or via people on farm?
Pam Ruegg: Within the last few days, the initial USDA dollars have come into Michigan to look at the epidemiology of how has this spread among farms. They've released some preliminary results of this and there's been a lot of testing on the initial farms.
The virus is not thought at this time to being spread by wild birds or migratory birds. It came in with infected cattle and the transmission between farms, they believe at this point is a result of the same things that other diseases transmit between farms: shared people, and workers going between farms. They know for sure that's happened between the dairy and the poultry farms.
There were people working on dairy farms that were also working on poultry farms or who living with people working on poultry farms. That's a route of transmission. There's a lot of work being done looking at milk trucks and the rendering trucks, the dead stock trucks, the boots of people.
So right now, the emphasis is on reducing movement, increasing biosecurity, being cleaner, and limiting the number of people to farms to people that are essential to come to the farms and also reducing movement of farm workers between different farms and between poultry and dairy.
If H5N1 is here to stay, as an industry, do you think that we can handle consumer perception?
Nicole Martin: Consumer perception is obviously a big risk for us, right? We're just coming off of COVID. This is another virus that's being spread. There's a lot of press running around about this issue. I think that that is a concern that we have to be careful about and I think being transparent and being cautious about making overtly confident statements at this point is important, as well as doing the science and having that backup. What we expect to see happening is that pasteurization is an effective tool to reduce this virus and that the pasteurized milk supply in the United States is safe.
And then I would kind of go on a tangent a little bit about that, right? Because not all of our products in the United States are pasteurized. And so, I think from a consumer-perception standpoint, a lot of consumers are probably not going to see the difference. If someone gets ill from consuming a raw milk product versus a pasteurized product, that's still going to have an impact on consumer perception of the safety of our system. So that's a big concern for us.
There are a number of groups working toward developing the science on the food side because the more exposures we have, we all know the higher risk is that the virus doesn't just jump from dairy cattle into humans, but jumps from human to human. And that's sort of a worst-case scenario and I think really puts the point on is this virus here to stay? And I'm not an epidemiologist, but that's certainly the concern that I would bring up.
There's a lot of information out there that suggests that dairy youngstock—or dairy calves—may not be as clinically affected as adults, is this true?
Pam Ruegg: So, to a lot of these questions, I'm probably going to answer, we don't really know for sure. I'm going to give you anecdotal evidence from talking to veterinarians who are directly treating animals on farms. I also work with nutritionists who are working with herds during outbreaks and managing the nutrition.
And I've talked to a number of farmers who are affected and they've shared information but we don't have a lot of data yet to say this is definitively correct. So, with everything I say I want to disclaimer on this is today. I can tell you every single week for about the last eight weeks, I've learned more about this particular outbreak.
Relative to calves, there are some farmers who believe their calves have been ill, but they don't think they're very ill. In fact, a lot of farmers don't think most of their cattle are very ill. So, what I've heard described on the calves is, “oh, they're kind of like a kid with the flu.” They've seen some decreased intakes, they've seen some more lethargic calves, and during an outbreak where they've confirmed that they've had the disease on the farm.
So, I believe it's probably likely that there may be some calves affected, but we don't know for sure yet.
What kind of personal protective equipment (PPE) should we recommend for personnel dealing with cows or processing milk?
Pam Ruegg: The CDC has recommendations of what sort of PPE should be used, and I recommend we follow the recommendations of public health authorities.
I'll also make a couple of comments relative to why maybe people aren't, because people aren't following those recommendations on the farms. And one of the reasons is people that are working in the milking parlors, and the people that are working treating the sick animals during an outbreak, are working really hard. They're tired and it's hot and it's hard to implement a lot of this stuff when they don't perceive an enormous risk to themselves. So, I think a couple of things to think about. There've been three confirmed cases that I'm aware of in humans in the US, one in Texas and two in Michigan. Two of those cases have been ocular infections where they have conjunctivitis.
I don't know the route of transmission of those, but I'll tell you, when I work in a milking parlor, I always get milk splashed in my eyes and we know there's tons of viruses in the eyes. I think personally, this is my opinion, a minimum level of protection for people who are going to be exposed to milk should be glasses. Safety glasses. I think the CDC is recommending face shields. I think people who've tried face shields have not adopted them very long, so I think we’ve got to work with people where they're at in their jobs.
And for the people working in milking parlors who aren't doing anything, any kind of eye protection is better than nothing. The other worker in the United States that got a lot of press was the worker who had a respiratory infection.
That worker, my understanding is—and I'm fairly confident on this—that worker was directly involved with the treatments of sick animals. Now the treatments for this disease are supportive and the animals run high fevers. Generally, the treatments are aspirin boluses and oral rehydration.
I'm a veterinarian. I've done those treatments myself. When you are giving oral treatments to large cattle, your head is right next to their nostrils. And so, if we've got any sort of respiratory transmission risk, which has not yet been confirmed, but if we do, I think personally if I was doing those treatments, I would be wearing a mask while I was doing the treatments.
I think that we should be following the CDC guidelines, but if your people won't do that during an outbreak on the farm, we should really be stressing eye protection, mask protection, and wearing gloves so that you can easily remove any milk contamination.
What do we know about the study that looked at milk samples prior to the clinical presentation of the disease?
Nicole Martin: Fortuitously, one of the affected farms that ended up testing positive had been taking bulk tank milk samples and saving those for about a month prior to the point where they had a clinically affected animal that tested positive.
They were able to go back and test those bulk tank samples that they had saved, and identify that the virus showed up about 16 days prior to any political signs of infection in that herd.
So, I think that's one of the pieces of this outbreak, in the risk of spread and infection, that's really important for us to understand is how long is that virus present there prior to us being able to really see it in the animals themselves.
From a high-level, what is the clinical presentation of H5N1 in affected animals?
Pam Ruegg: Clinical signs of the disease are kind of an interesting scenario. The signs are nonspecific to a certain extent, and what you'll typically see is in your lactating herd, you'll see a bunch of animals with high fevers, and these fevers in the most severely affected animals are really high. I didn't believe it when people first started telling me what they were, they're like 107, 108 degrees in the worst infected animals.
And so you'll have high fevers, you'll have a dramatic drop in milk production. The milk looks abnormal, okay, more colostrum-like than milk, and that'll occur somewhere in about 10 to 15% of the animals.
As initial reports were coming out people said, “Well, it's only in mature animals in late lactation.” That's not true at all. It happens in every stage of lactation across the herd. It happens in first lactation animals, it happens in fresh animals, but you do tend to see more clinically affected animals that are older. It's pretty interesting.
I've talked to three farmers who have some type of precision dairy technology on their farms, and these farms have their alerts. It could be rumination, it could be feed intake, it could be temperatures. Often the first thing they see is these alerts double or triple. So, you're going along at a steady level and they get these alerts go off, which they come and they look at their alert list and they're like, wow, what's going on?
There are a lot of sub-clinically affected animals out there apparently. And I talked to one particular veterinarian who was working with many animals on a farm. He said he was walking through the barn and in a group where they had quite a few affected animals—10 to 15%—he decided to stick thermometers in healthy-looking animals, animals that were up and eating. He said every animal he tested in that pen, even the ones that appeared healthy, their temperatures were higher than expected. They were like 103°F, 103.5°F, 104°F.
The other thing that happens universally in farms, and this is terrible, but about a week to two weeks going along with the bulk tank on farms that have cats, all the cats die. And so many farmers, if they find dead cats, that's better than a PCR test. If you've got dead cats in high fevers in your animals, that's something people are looking at on a very practical basis as an indication of the disease.
What do we know about humans ingesting raw milk and raw cheese?
Nicole Martin: Nothing. But that being said, we have some preliminary evidence that would suggest we should exercise some caution around this topic. Because of one, the high virus in raw milk from infected animals. We know these raw milk products have exceptionally high viral loads.
We know that the consumption of this infected raw milk is associated with deaths in farm cats. There have been some trials with ferrets. I think we have to be careful there's nuance here, right?
Do I think that the milk going into the general milk supply is likely to have this unique combination where we have these really high viral loads and people are consuming that? No, I think that's fairly low risk. And in general, I think the food safety risk is low, but we can have the conversation about if folks are drinking raw milk with these high viral loads, that certainly presents a risk that we should be concerned about.
There's enough evidence to be concerned about that. And again, I don't think that there's any reason to believe that this is a gastrointestinal transmission route. Likely what's happening is when you consume any food product, there's worth a nasal exposure to whatever you're consuming. And I think that if that's the transmission route, then that's most likely, right? So exercise caution. We know very little for sure at this point.
As a USDA-accredited veterinarian, what is your take on if you are at a dairy and you see cows that you suspect may have H5N1 ethically and legally, do you need to test and how does that work?
Pam Ruegg: Michigan’s State Department of Agriculture has declared an “extraordinary emergency,” meaning veterinarians are supposed to be testing suspect animals in an accredited laboratory and all positive tests—these are PCR tests—are required to be reported. So, it's a reportable disease if the test is done.
One of the biggest concerns is we can't fully control the disease unless we know who has it. I think it's very important that people comply with trying to identify infected herds.
However, there's a real practical ethical dilemma there because if the producer does not want to have their herd tested, they're probably not going to call the vet. They don't have to call a vet. So, there's a really fine line there, I think in maintaining veterinary oversight of herds and following the regulations. And that's between the individual veterinarian and, and their clients and, and the personal ethics of, of those groups. Legally the veterinarians are supposed to report.
If dairies continue to choose not to test and poultry trade in the area is affected, are there any legal actions that can be taken?
Pam Ruegg: I have no idea. I mean, this is the United States and there could be a legal action taken on virtually anything. So I would assume the answer is yes, but I'd also say in our initial outbreak in Michigan—and there's approximately 99 or 100 herds that are confirmed from PCR testing in the United States to be positive for this—of those, there's 25 of those have been confirmed in Michigan.
We also have a number of poultry farms, which were confirmed at the same time, and a USDA Epidemiological Strike Team came in early April and has done a lot of testing throughout the state and issued their final report last week. And they were looking at potential routes of transmission to both poultry and to the dairy farms. About two-thirds of the dairy farms were likely infected by movement of cattle between farms.
About a third, maybe a quarter to a third of the herds—were closed herds. Confirmed closed herds. And the poultry farms that got infected with the H5N1 Texas ancestry strain, so this is the strain.
It came to Michigan in sub-clinically infected cattle that were asymptomatic and remained asymptomatic for about 7 to 10 days on the farm before it broke.
And then soon after that, we had a large poultry operation that broke. And there was a lot of concern on how this happened because the poultry operations in Michigan have been buttoned down hard because of the migratory avian influenza, which they had two years ago. And so they’ve got huge biosecurity.
Well, what they have determined with this Texas ancestry strain, is that the most likely route of transmission was employees who worked on dairy farms and maybe also worked on poultry farms. So that's been confirmed.
Also, there were employees who were partners. Maybe one of the partners, like the wife, worked on a dairy farm and the husband worked on the poultry farm, and this was unknown. So, a huge risk factor that was identified in this analysis is working amongst either multiple farms or multiple industries.
If you're looking at the poultry farms in our poultry industry—which is a major employer in our area—it laid off 400 people about a week ago. I'm pretty sure that most of the people who had shared employment with dairies and poultry farms no longer have employment, but at least not on poultry farms. So, I think when we look at the poultry issue, more biosecurity and a very strict barrier away from contact with people who are working on infected farms.
What do we know about animal-to-animal transmission? Do we know anything about immunity post-infection, and how long that might last?
Pam Ruegg: I'm going to answer the second one first. I'm also going to say two months ago I knew nothing about the subject. So, I'm not an expert really, but I have learned a little bit over the last couple of months.
I saw some really interesting data out of some of the original animals that were testing out of, I believe they were out of Texas, and I believe the testing was done at Iowa where they went in and they took milk samples and tested for viral load.
So, you're looking at the PCR levels and these animals when they detect them with clinical signs, they have tons of virus in the milk. So, the CT thresholds are like 5, I mean they're very, very low. And then what in this group, I think it was 28 or 30 animals, they tested them weekly for about, I don't know, four to six weeks.
And those PCR Ct (cycle thresholds) went up and up and up until about four to six weeks out there, almost all of the animals are negative and I think that threshold is 38 or 39, somewhere in that area. They didn't stay positive for a really long time.
They also presented some data from a subset of those animals where they were doing enzyme-linked immunosorbent assay (ELISA) testing on blood looking at antibodies. And the antibodies went up dramatically in these animals over the same period. So, it appears that dairy cattle are effectively mounting an immune response and most of the animals don't get very sick.
So, it's only 10 to 20% of the animals where you get animals with really obvious clinical signs. But probably most of the animals are infected or a lot of them are, or you'll have a lot of animals with low fevers. So yes, it appears they do mount an antibody response and it appears that the amount of shedding of the virus overall drops pretty dramatically.
Although I will say I have talked to veterinarians who are continuing to test animals on farms, and there are animals that remain positive on PCR tests for quite a long time. So, there is individual animal variation and I think the testing that people are requiring for exhibition for movement, that's money well spent.
The first part of that question was the cow-to-cow transmission. Cow-to-cow transmission is a great question. We don't know fully the answer to that. So there's a lot of people in the field, and we know there's a lot of virus in the milk, and we know that animals get infected. If you bring in an animal, it appears the clinical syndrome at the herd level is—you bring in an infected animal, subclinical, nothing happens for a while, incubation period, you find some dead cats and you're like, oh no, I got dead cats.
And then the next day you've got a whole bunch of animals with really high fevers and your milk production drops and you got all the clinical signs that go with it. That kind of goes along with what we're seeing in animals, but we don't really know how that transmission among animals happened. There's a lot of conjecture. People are like, well, it's probably in the milking parlor from cow to cow to cow because there's so much virus in that milk. We have no idea if that really works. And then there's some thought that there's respiratory transmission, but nobody has confirmed that yet.
So I want to remind everybody, we're really early in this. I am a person who likes to speak from data and I'm sitting in front of a whole group of people not speaking from data hardly at all. So, I think we have to be very cautious, but can't likely be transmitted in a respiratory fashion. I think it's probably likely—it’s an influenza virus. So I think we've got to think about minimizing contact, minimizing the airspace of infected animals as well as minimizing contact with help.
Any thoughts on the virus showing up in wastewater that's not associated with positive dairies? Are there processing facilities that may be getting positive milk, if a local dairy has yet to be tested?
Nicole Martin: Yeah, so I'm certainly not an expert on wastewater, but I will talk about the processing level. It's a step removed from any ability to determine any clues as to whether there's an infection there, right?
When we're on the farm, we can look for clinical signs, we can look for dead cats. We have fewer markers that help us to evaluate what could be going on on the processing side. We are getting in milk and tanker trucks and we have no ability to say, “Okay, maybe there's something going on or not.” So there's another level of uncertainty that shows up there. And I think that, right now, what we're encouraging folks to do is keep an eye on infections in your area. Although we all know that milk moves across state lines.
We get milk in from Pennsylvania, we get New York milk goes into other states. So that's not a completely foolproof method, but there has to be an awareness at that level because we don't have the ability to keep an eye on symptoms or keep an eye on the herd at the processing level. So, I think it's a good question. That is kind of an evolving issue and we talked about PPE. Certainly, I don't think we need to be getting everybody in Tyvek suits at the processing level. But we do have to keep an eye on what's happening in our area and in our milk from a processing perspective.
We feed a lot of whey to cows. What are the implications given the high viral loads or what things should we look for?
Nicole Martin: Sure. It depends on how we generate that whey. Some whey is generated without a heat treatment and some whey is generated with a heat treatment. At this point, we're pretty encouraged about the impact that heat treatment has on viral infectivity. So that's one thing to keep in mind.
The other is a lot of whey is generated from cheesemaking and a lot of times we have acidification when we make cheese. There's also a reason to believe that this likely has an impact on infectivity, but we don't have the data to support that yet. Those are experiments that we're beginning at Cornell to work on answering.
But obviously, if we're in a situation where we're not heat-treating the whey, it's not acidified, and they're going back to cows. We don't yet know what kind of separation into the protein fraction and the whey fraction there is on this virus yet. So that's another factor. But you could imagine a scenario where there is a high viral load in a whey product that's being fed back to animals. That would be a concern to me.
Certainly, the amount that they're consuming would play a role as well. Viral load and consumption amount, as well as the susceptibility of the animal, are all things we don't know yet, but those are all factors that need to be considered.
Can you explain the tropism of the virus to the udder?
Pam Ruegg: This is a great question. It's actually really a cool thing. If this was an abstract concept, I would find this fascinating. The receptor cells are these sialic acid receptors and, in dairy cattle, they're in the udder. And we don't know why.
In cats, they're in their neurologic tissue. I think in humans they're in the respiratory tract. But the reason we get so much virus in the mammary gland is they've got the right cell receptors there. The reason cats die is because they've got these receptors in their neurologic tissue. So that's why we're finding the virus where we find it.
How do we think this virus could affect state and county fairs?
Jess McArt: I will say that we just got an email from New York State today that all cows in New York will need to have a milk test within seven days of transfer to a show, with costs covered by the USDA. And those tests have to be done at certain accredited labs. So, the logistics of that might be difficult, but at least for New York State, that's a requirement for New York State shows.
Pam Ruegg: All exhibitions with lactating dairy cattle and poultry are canceled in Michigan.
What concerns are we anticipating from consumers and how can we be proactive on informing the public and answering the questions that they have?
Nicole Martin: Yeah, this is a really, really good question. And I don't do consumer research and I am really grateful for the people who do because I don't understand them. But consumers are driven by a few things and fear is one of them. And so obviously we're concerned about public perception because this is a potentially really frightening event.
I think that the more we can rapidly do the science, the more we get ahead of the what-ifs. And we've already seen a lot of what-ifs. And I think that's why it's so important that there is a network of individuals, academic institutions, government institutions, and industry coming together to answer some of these questions so that we can get facts out there because that's what's going to inform the best response to this.
As Pam said, we are working on very little data. It is being generated, but I think the more we can get that factual information out there, the more we can assuage fears of consumers.
We know there are concerns that this year’s World Dairy Expo may be canceled, do we know anything about that?
Pam Ruegg: I do not know if World Dairy Expo will be canceled. I think that would be a last—I mean I think that would be an extreme measure. I believe Wisconsin is requiring testing for animals now and just started that. There's probably going to be some testing requirement, which is a good idea at this point.