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As the H5N1 influenza debacle at the Universal Ostrich Farm in British Columbia finally comes to a close, part of me wants to ignore all the crap that’s coming in, but there’s value in recapping this incident in an effort to help move us forward.

Recap: A large flock of captive ostriches was found to be infected with H5N1 influenza in December 2024. Contrary to federal legal requirements to report this disease immediately, the farm hid the issue and didn’t do any of the things typically required to respond to a detection of this high-consequence virus. It’s been reported that 69 birds died and 300-400 birds survived (they never could come up with an exact number). When the outbreak was discovered, the Canadian Food Inspection Agency (CFIA) got involved, as is their mandate. As per standard protocols for detection of H5N1 flu in poultry (captive ostriches are considered poultry by international designation), a cull order was issued immediately. However, the farm fought the order by trying to appeal and sue the CFIA, while taking no measures to try to control the spread of the virus – if fact they did the opposite, showing pictures of people posing with the birds without personal protective equipment (PPE), and inviting a convoy of farm supporters onto the grounds. Ultimately, the case made it to the Supreme Court of Canada, which issued one last temporary stay order on the cull in late October, but ultimately declined to hear the last appeal. As a result, CFIA completed the cull of the remaining birds on November 7.

Make no mistake, the ostriches are the victims here. They had bad luck in being exposed to H5N1 flu in the first place, and they had little chance of avoiding a cull because of the mess of a farm on which they lived. But this case moved quickly from being about disease control to being about politics and fundraising, and the birds got caught in the middle.

Why was a cull done?

A cull is a standard approach to controlling H5N1 influenza in poultry because of the risk to animals and people. It’s done to contain the virus and reduce the risk of further transmission to other birds, spillover into mammals (which increases the risk of the virus adapting further to transmission between mammals), infection of people (given this virus has a historically high mortality rate) and, of most concern, recombination with other animal and human flu viruses (which is how all pandemic flu viruses originate).

Were the ostriches infectious in December 2024?

Yes they certainly were, and likely at great risk of infecting wild birds, wild mammals and any people or other domestic animals on the farm. It was subsequently determined that the strain found in the ostriches was a variant that has caused human infection and had some potentially concerning mutations.

Were the ostriches infectious when they were culled in Novemeber 2025?

Probably not. In a group like this, the virus probably burned through the entire population by January or February. Long term shedding of flu virus in infected birds is unlikely, so with a group this size over 10 months, realistically the flock would have had to be reinfected to sustain transmission. Could that have happened? Maybe, but probably not. Unfortunately ” but “probably” isn’t an acceptable threshold for control of this disease. If we don’t know the virus is gone, prudence dictates that we assume it’s still there. That’s the approach that CFIA (understandably) takes with highly pathogenic avian influenza like this.

Was there an alternative to culling the birds?

That’s a big “maybe” with lots of caveats. While culling is the international expectation, countries can take alternative approaches if they can show they’re taking other measures to adequately contain spread of the virus. That’s not expressly defined though, so it’s a grey area for a regulatory agency that doesn’t like to work in the grey zone for a lot of good reasons. It would require reliable isolation of the birds, strict infection control practices, testing, monitoring and documentation. That’s tough to do in general, but t’s really tough with outdoor birds and uncooperative owners.

At the time the outbreak was happening, it was fair to say trying to contain the virus by any other means was not reasonable. The risks were too high with the setup they had. But the ball got dropped, and so there we were ten months after the fact… at that point, testing could have potentially made more sense. That’s no easy feat either, though. Ostriches are big birds that can cause significant injury to people handling them, especially where there are poor (to non-existent) handling facilities. Trying to stick a swab down the throat of a large bird that can split you open with a kick is hard to sell.

In order to make testing work, each bird would have needed to be caught, identified, and tested. If there were zero positives in the group, I’d be pretty confident the group was negative. That’s theoretically possible. However, there would likely have been a need for ongoing monitoring to have confidence in the negative group status. Since the farm hid the disease initially and showed no interest in implementing disease control measures, it would be hard to convince anyone such an approach could have been effective.

Furthermore, even if the World Organization for Animal Health (WOAH) thought such an approach for controlling the virus was adequate in this flock, that doesn’t mean all countries would agree. Any country could then restrict importation of poultry (or other food products) from BC or even all of Canada on the premise that Canada was not protecting its food supply. Even if it’s a dodgy claim, a country with an agenda or that wants leverage for negotiations could play that card, and be successful.

When there’s potential risk to animals, humans and multi-billion dollar industries, the bar for disease control is obviously going to be very high. So was an alternative to culling the birds possible? Yes. Would it have been easy? Certainly not. While easy isn’t a requirement, in this case it wasn’t that it was just a hassle, it was that there was a good chance it might not ultimately be possible.

Did the ostriches have herd immunity to H5N1 flu?

For a group of supporters who were comprised of a large proportion of individuals who were anti-vax (and anti-PCR, and anti-public health and some people who don’t believe viruses exist at all), they put a lot of attention on herd immunity (which we typically try to achieve in a given population of people or animals through vaccination). It’s very unlikely this group was immune to H5N1 flu. the birds that were exposed and fought off the infection would have some immunity, but we know that immunity to influenza after natural infection isn’t great or long-lasting – that’s why people and animals can be repeatedly infected with flu. Some of the birds might have been immune, or at reduced risk of severe disease. Some were probably previously infected but are not immune. Some might not have been exposed and were not immune. As a group, it’s very likely that there would have still been susceptibility to re-infection if there’d been another exposure to the virus, so there was still risk.

What about the “research value” of the ostriches?

The farm talked a lot about how these are no longer meat birds, but rather a “research flock.” However, they were never able to present any information about valid research for which the birds were being used. They didn’t indicate that there was ethics approval for research on the farm (a basic requirement for research involving animals). They didn’t even know exactly how many birds they had, and the birds had no form of identification (tags, microchips); without basic information like that, the farm can’t be a legitimate research operation.

Even though the remaining birds survived H5N1 influenza, that still doesn’t make them inherently useful research animals. We don’t know how many fought off the infection (something we know many birds of some species can do) or weren’t actually exposed. The birds that survived an infection may have antibodies against H5N1, but so would any other animal that survived natural or experimental infection, so there’s no unique value there.

Where do we go from here?

Hopefully we can look back on this case and salvage something positive from this mess and the unfortunate ending for the birds. There are a few key components:

The Supreme Court has re-inforced the appropriateness of CFIA’s disease response. This is important since it might reduce the chance of future lower court successes with appeals and stays. It’s fair to criticize CFIA and demand that they have oversight. It’s also fair for CFIA to say “we have to contain this disease for the protection of animals and people, and we need to do it quickly.” No one at CFIA celebrates when they have to cull animals. They do it as an unfortunate but necessary part of their mandate to protect animal health, human health, agriculture and the food supply.  Allowing people with agendas to weaponize the court system creates risk.

There may be valid arguments for approaches other than a cull, in certain situations, as H5N1 flu is now an endemic disease in wild birds. However, this needs to be done carefully, with a lot of transparency, effort, structure and excellent care. In other words, exactly the opposite of what happened here. A mechanism to promptly evaluate a potential alternative, with a clear approach, set criteria to review (what, who, etc.), a very rapid response and no appeal process would be interesting to investigate.

As part of any alternative approach, there would need to be excellent interim containment. If a farm wants to convince CFIA to take a different approach, they need to do absolutely everything possible to contain the disease when an outbreak occurs. If it can be done with minimal risk, it’s potentially viable. If it creates risk in the interim, it’s not. Even if this farm had done the exact opposite of what they did, and diagnosed the issue quickly, reported it, properly disposed of dead birds and enacted strict infection control practices, it’s debatable whether an exemption during the acute disease period would have been viable because of their set up. You can’t contain a few hundred large birds (producing lots of virus-laden snot and feces) outside in an area with abundant wild birds, with no indoor isolation options or handling facilities. Without appropriate facilities and management, it’s not an option. That’s not CFIA’s fault. That’s a choice by the farm about how they operate. Raising birds outdoors isn’t bad, it just create risk that any farm needs to accept. And when it results in disease, there are consequences.

We had a high consequence virus on this farm, they handled it horribly, the virus in question had some mutations that created even more risk, and nothing bad seems to have come of it (that we know of, at least) in terms of disease spread. Does that mean none of this made sense?

  • No – we just got lucky, and you only get lucky so many times with a high consequence infectious disease that has pandemic potential.

It’s really sad how infectious disease control (and beyond) has gotten so politicized. This went from an issue with one group of infected birds to having a convoy on the (quarantined) farm, massive misinformation, dodgy “media” stirring up hate, threats to experts and people doing their jobs, massive fundraising and grift, largely by people who likely don’t care whatsoever about those ostriches. It also cost taxpayers a huge amount of money, and took up time a resources that could have been much more effectively spent elsewhere. The ostriches were political pawns and an excuse to complain, raise money and have a party at the farm. We need to move beyond that component of this issue and come back to the valid disease control questions that can and should be discussed going forward.

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When it comes to food safety risks with H5N1 influenza, we know it’s a problem with raw (unpasteurized) milk from cattle, so I often get asked if it’s a concern with milk from other animals, such as goat’s milk. It’s a good question. My typical response has been that we really don’t know. There haven’t been any reports of H5N1 flu in other dairy species (except for one report at this time last year of infection in neonatal goats on a farm in Minnesota that had infected poultry), but we have a lot more dairy cattle living on much bigger farms in North America. So it’s hard to say if cattle are actually at greater risk, or if we’re just more likely to recognize problems on a big dairy where the animals are monitored closely.

There is now a report from the UK about H5N1 infection in a single ewe (a female sheep) in Yorkshire, which was on a farm that also had infected captive birds. While this doesn’t tell us about the risk in goats or the overall difference in risk between dairy cattle and other dairy animals, it shows that cattle are not the only dairy species of concern. 

The ewe tested positive on a milk sample, which was collected as part of the response to the infected birds on the farm (a smart surveillance approach that helps with early detection of spillovers and helps us understand transmission risks and patterns). Only one sheep from the flock was positive, but we have to assume the risk is likely broader – if one sheep can be infected, then other sheep could be too, if exposed to enough of the right virus.

The infected sheep was culled, which is understandable, as it removes the risk from that sheep. Unfortunately but it also removes any ability for us to learn more about what H5N1 flu does in a naturally infected sheep. It would have been ideal to isolate the sheep and monitor it for signs of illness and test it for virus shedding, but that’s not always possible. 

There are a few good take-aways from this report:

  • It shows the value of surveillance. If they hadn’t tested the other animals on the farm, we’d have no idea the sheep was infected, as the sheep did not appear sick.
  • Presumably, this was a direct spillover from the infected birds on the property. Hopefully that means the virus in not established in sheep anywhere else (like it is in dairy cattle in the US), and that this was an interesting one-off infection but not of broader concern.
  • If there really was only one infected sheep, removal of that ewe may have prevented it from infecting other sheep, and the other sheep all tested negative. I hope there will be a bit more testing on this farm to make sure there are no secondary cases.

I guess we can’t rule out the possibility that the sheep infected the birds. However, since they tested all the other livestock and only this one sheep was infected, it’s pretty safe to assume this was a direct bird-to-sheep spillover. Sequencing of the virus will help confirm this. Serological testing of other sheep on the farm would be interesting to see if there’s evidence of earlier infections.

Does finding H5N1 flu in a single sheep change anything?

No, not really. We know that H5N1 has spilled into a wide range of different mammals, and this just expands that list. We’ve assumed there’s some risk from other dairy livestock species, and this shows that’s a reasonable concern. We’ve also talked about risks from raw milk even before H5N1 was concern, there are lots of infectious disease risks with drinking any type of raw milk.

However, this report does raise the stakes a bit. We don’t want continued spillovers into mammals, because that increases the risk of this virus adapting to become better able to infect more mammals (including people). We don’t want endemic transmission in domestic mammals, as that increases human exposure risk. We also don’t want H5N1 flu in the food supply (but remember that pasteurization will kill the virus). 

UK Chief Veterinary Officer Christine Middlemiss’ statement sums things up well:

“We have confirmed the detection of influenza of avian origin (H5N1) in a single sheep on a farm in Yorkshire. Strict biosecurity measures have been implemented to prevent the further spread of disease.  

“While the risk to livestock remains low, I urge all animal owners to ensure scrupulous cleanliness is in place and to report any signs of infection to the Animal Plant Health Agency immediately.” 

The UK Health Security Agency (UKHSA) has said that avian influenza is primarily a disease of birds and the risk to the general public’s health is very low, but people should not touch any dead or sick wild birds they find. 

The Food Standards Agency advises that properly cooked poultry and poultry products, including eggs, remain safe to eat and avian influenza poses a very low food safety risk to UK consumers since the H5N1 virus is not normally transmitted through food.”

Awareness.

Diligence.

Good use of routine infection control and biosecurity practices.

Continued surveillance.

Those are the key factors for limiting the risk from this virus. 

The Washington State Department of Agriculture and the Oregon Department of Agriculture have issued a public health alert because of H5N1 influenza virus contamination of another brand of raw pet food, following the deaths of two more indoor cats from separate households linked to consumption of the pet food.

Details are sparse, but both cats were euthanized due to severe disease from H5N1 influenza. Authorities tested the cats and the food from open containers in the household as well as unopened food samples, and found H5N1 flu virus in all of them. This shows that the food was truly contaminated at the source, and removes the potential that the food got contaminated in the household by the cats or some other source. (In a previous raw food-associated cluster of H5N1 flu infections in cats, the manufacturer of the implicated food tried to suggest the diet was contaminated in the household and was not the source of the virus, which was a very weak argument, and definitely not the case here based on the additional testing).

The recall involves Wild Coast LLC Boneless Free Range Chicken Formula, lots 22660 and 22664, Best Buy day 12/25. However, given that we have multiple instances of fatal raw poultry associated H5N1 infections in cats from multiple companies, the risk probably extends beyond this product.

To avoid the risk of H5N1 influenza from raw pet foods:

  • If raw diets are to be fed, use a non-poultry based diet, and choose one that’s high pressure pasteurized to reduce (though it will not eliminate) the risk.

Image from https://agr.wa.gov/lookuptypes/recallfile/131

I think it’s fair to say H5N1 becoming seemingly endemic in US dairy cattle in the past year caught us off guard. The virus has spread widely within and between US dairy herds, has caused mild infections in a number of people in close contact with infected cows, has killed a lot of cats on farms (and a few from drinking raw milk from infected cows)… and it isn’t likely to go away any time soon. 

Dairy veterinarians are one of the higher risk groups for exposure from infected cattle because of their close and frequent contact with these animals, particularly when cattle are ill. Surveillance testing of people at high risk for exposure to H5N1 influenza can help us get a handle on how much (if any) under-the-radar cow-to-human transmission may be happening, so it was great to see the release of the results of just such a surveillance study in dairy veterinarians in the US (Leonard et al. MMWR 2025).

In this study, researchers tested blood samples from 150 veterinarians with cattle contact and tested them for antibodies against H5N1 influenza. The presence of antibodies would indicate previous infection, whether or not the person was ever sick from the virus.

Three of 150 (2%) dairy veterinarians were positive for H5N1 flu antibodies, but none of those reported having had signs of illness that could have been attributed to flu, and none reported working with dairy cattle that were known to have been infected with H5N1 flu. If that’s accurate, it could indicate a few things, including possibly:

  • working on farms where there was mild disease in cattle from H5N1 flu that was not recognized
  • working on farms where there was disease in cattle from H5N1 flu but the cattle were not tested for it
  • veterinarians were exposed to H5N1 flu in some other way from animals or the environment, such as through contact with other animals or raw milk. (One of the veterinarians who tested positive also had contact with infected poultry, so that’s another potential source of exposure)
  • veterinarians were exposed through unrecognized human-to-human spread of H5N1 (which would be the most concerning possibility)

One of the seropositive veterinarians worked with dairy cattle in Georgia and other cattle in South Carolina. Neither of those states is known to have H5N1 in dairy cattle (see map above from the report), but the degree of surveillance and (more importantly) reporting is variable across the US. This would suggest that testing of cattle in Georgia needs to be ramped up to see if they have unrecognized infected herds.

All three antibody-positive veterinarians “reported wearing gloves or a clothing cover when providing veterinary care to cattle (including a variety of clinical activities, such as pregnancy checking or surgery)”. That’s strange wording, since those are two distinctly different types of PPE. Virtually every dairy veterinarian is going to wear coveralls (a clothing cover) on farm, so that stat tells us nothing about how many of them wore gloves (nor whether glove use may have been suboptimal, as it often is on farm). There was no use of eye or respiratory protection, which is far from surprising and something the veterinary profession needs to improve, as we do a poor job of using respiratory protection and rarely use eye protection when we’re dealing with animals with respiratory infections, even when they could be zoonotic.

The fact that all three antibody-positive veterinarians reported no obvious consequences of H5N1 flu infection is good news on many levels. However, asymptomatic infections raise some concerns, since if people are asymptomatically infected but still infectious, it may allow the virus to spread silently through the population, at least for a while. We have no idea if infected people shed the virus at levels that can infect others, but it’s something for which we need to be on the look out.

Any H5N1 flu infections in a person is bad, because of the potential for severe disease in the person and, even more importantly, the potential for evolution of the virus to transmit more easily among people. The more H5N1 encounters humans, the more opportunity it has to become adapted to humans. Infection of people concurrently infected with human flu virus strains creates opportunities for recombination of both viruses, which can lead to rapid and significant undesirable changes and emergence of new strains.

This is far from a doomsday report, but it highlights some things that we need to keep watching. It also shows why we need more effort to contain the spread of H5N1 flu in domestic animals. The data here are a bit limited, but they’re an important step in our understanding of this virus. A parallel study of the general population would complement these data, as would more focused study of veterinarians and farmers from affected farms, and veterinarians working with other species.

The more H5N1 influenza continues to circulate in wild and domestic birds around the world, including here in North America, the more we have to be concerned about exposure of pets to H5N1 influenza through raw food diets. Recent documented infections in cats fed raw meat from infected birds have highlighted these concerns. For more information on the risks of H5N1 influenza from raw diets for pets and associated risk reduction measures, check out the latest quick podcast on Worms&GermsPod.

Find all our podcasts on most major podcast directories, or access them here directly through your web browser.

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Addendum: The Oregon Veterinary Medical Association has indicated in a release that the cat discussed below was euthanized because of the severity of disease. That’s more consistent with the severe disease that’s usually reported but I think the discussion below still applies since this seems to have been an initial primary respiratory disease presentation. It probably still shows that there can be a primary presentation that overlaps with more common presentations so we need to consider H5N1 beyond severe neuro or sudden death cases.

I’m not commenting on every new report of an H5N1 influenza spillover infection in a domestic animal because it’s not really news anymore, but that doesn’t mean they’re not concerning. Spillover infections definitely are a concern with this virus, and we expect these spillovers to continue as long as this virus is circulating in wild birds (or in large numbers of dairy cattle, as it is the the US).

Nonetheless, a recent case of H5N1 influenza in another cat in Oregon highlights something important, because it’s different from previous cases. Most reported cases of H5N1 flu in cats to date have been of severe disease, usually with neurological signs, but it’s been unclear whether this is because infected cats typically get severe neurological disease or whether we’ve only been testing the cats with severe disease. It remains unknown how often infected cats get milder disease, and that’s a really important testing consideration, for both clinical patients and surveillance testing.

Respiratory disease in very common in cats, especially outdoor cats. Knowing whether flu should be a consideration in your average cat with an upper respiratory tract infection is important for determining how they are managed in a clinic (to avoid transmission to staff and other patients) and how they should be managed at home (to avoid transmission to family members and other animals in ad around the home). 

In contrast to previously described severe cases in cats, the recent case of H5N1 in a cat from Oregon was described as having a much more typical respiratory tract infection. “A veterinarian examined the cat after it exhibited symptoms including a fever, runny nose and eyes, lethargy, difficulty breathing and loss of appetite.” Although difficulty breathing isn’t typical for a run-of-the-mill upper respiratory tract infection in a cat, it is consistent with pneumonia, which can occur secondary to any viral infection. The news report is light on clinical details, but if this case was actually was more akin to a typical pneumonia that we might see in cat secondary to other more common bugs, it (long with a few other milder cases where cats have recovered) suggests that we need to vastly expand the cats we should consider potential H5N1 flu suspects. It means we need to focus on more than just the severely ill cats with respiratory and neurological disease. At the same time, it’s tough to say how wide a net we should cast, given the commonness of mild upper respiratory tract disease in cats.

At this point, the key is flagging risk factors for exposure in these animals, including outdoor access, contact with farms and being fed raw poultry diets. In combination with respiratory tract or neurological disease, we should consider the cat an H5N1 flu suspect unless another cause is evident. 

A challenge with this is that cats with outdoor access are also the main risk group for any typical feline upper respiratory tract infection, so including them greatly expands the pool of suspects and can make practical management harder. Nonetheless, at least for now, we should probably still be flagging any outdoor or indoor-outdoor cat presenting with respiratory disease beyond the routine upper respiratory disease complex as a potential flu suspect, with corresponding considerations for testing and infection control.

Should we consider any outdoor/raw fed cat with any signs of respiratory disease a flu suspect? Maybe. It’s certainly possible that H5N1 can also cause typical flu-like disease/upper respiratory infection. I’d recommend not completely discounting it in any case, but paying particular attention the more severe the disease is, and the greater the cat’s risk of exposure.  

As with most emerging diseases, this is a fluid situation and it’s tough to figure out where to draw the line in order to balance protection and practicality. As we learn more, that line will likely move, so we must keep an eye on new developments and take reasonable measures in the interim. Personally, I always prefer to err on the side of testing more and being more aggressive at the start, and then de-escalating when we know more, but there’s also a practical limit to how far we can go with that. 

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As H5N1 avian influenza continues to spread in wild birds and spills over into domestic birds and mammals of many kinds, we’re becoming more aware of the risks to domestic mammals and there are more questions about test selection and interpretation. Fortunately, testing for H5N1 influenza is relatively straightforward.

  • For cats and dogs, the recommended samples for testing are typically oropharyngeal swabs, plus or minus nasal swabs (plus or minus other tissue samples of the animal is deceased. 

What tests are currently being run by veterinary diagnostic labs?

PCR is the most accessible and useful test; diagnostic labs basically offer two types of influenza PCR: matrix / pan-influenza A PCR, and strain-specific PCRs (see below). Different commercial labs offer different tests or combinations of these tests, and the tests offered may also vary by species (i.e. what’s routinely done for dogs can be different from cats). Test offerings may also change over time as labs adapt to the ever-changing situation with flu in different populations. If influenza is a consideration in your patient, check with your lab regarding which tests they will run (particularly if you are submitting samples for a respiratory PCR panel) and how to interpret the results, including whether or not the test will detect H5N1 flu if that’s a concern.

Influenza A matrix PCR (aka pan-influenza A PCR)

This test will detect RNA from any / all influenza A viruses. A positive test confirms that flu virus is present, but not the strain (and not that the virus present is necessarily viable). Knowing the strain is important to understand how the animal might have been exposed and transmission risk. It’s a good first screening step, but if it’s positive we need more testing. If a cat was positive, it could mean it has a human seasonal flu strain (people sometimes infect their cats, and ’tis the season), or it could have H5N1 influenza, or another flu strain (e.g. a low pathogenicity flu strain which can cats sometimes get from wild birds, or potentially a swine flu virus if they have contact with pigs). Really rarely, but importantly, an animal could be infected with a combination of different flu viruses. Our concerns about and responses to these different scenarios are really different, so it’s important information to get. 

Strain-specific influenza PCR

These tests target specific influenza strains in different species, like canine H3N2, canine H3N8, avian H7N2 (found sometimes in cats) and human H1N1 (which can spill over sometimes into dogs and cats). It’s important to be aware that these are strain-specific tests, so an animal that just has H5N1 influenza will test negative on the H3N2 test, for example.

H5N1-specific influenza PCR 

As the name suggests, this test is specifically for H5N1 influenza, and we can be more confident in the result if that’s the strain for which we’re looking. The downside is that it won’t detect co-infections with multiple flu strains. The odds of a dog having H3N2 canine flu or H1N1 human flu and H5N1 avian flu at the same time are REALLY low, but that would be a REALLY concerning situation, so it would be nice to know. It’s more relevant when there’s higher non-H5N1 flu activity in the area as well, since that would mean there’s a greater chance of a hidden co-infection.

In order to provide the best possible information without over-testing every sample, labs will sometimes perform different tests in sequence: 

Run matrix PCR; if positive, then test for H5N1

This adds a step, but it’s usually a quick one, and we find out whether the animal has a flu virus and if so, whether its H5N1. The same issue with not identifying co-infections applies here, because there’s no testing for other flu strains.

Run matrix PCR, then test for non-H5N1 strains; if negative, then test for H5N1 

This works too. It adds a bit of extra time/work, and the more steps that are required, the greater the chance of a test error, but it gets to the same result pretty quickly and gives us a specific H5N1 result. The main theoretical issue is that we could still miss a coinfection (in this case because the H5N1 test isn’t run if any of the other strains are detected). 

Run matrix PCR, then test for non-H5N1 strains; if negative, then refer to another lab for H5N1 testing

This slows things down more and adds in some uncertainty as it requires sending the sample out for follow-up testing, which is another step where human error could affect things. It also misses co-infections.

Run matrix PCR, then test for non-H5N1 strains, then test for H5N1; if negative, stop and call it a generic influenza A positive

This isn’t ideal but still tells us a lot. In most cases nowadays, if the sample is matrix positive and negative for all the other main flu strains, it’s probably H5N1 flu, but pets can get spillover infection of other strains that aren’t included in strain-specific tests. If they stop here, it’s functionally okay but not ideal. I’d want to try to get followup testing of any matrix positive, type-specific negative samples (and would treat them as H5N1 positive until proven otherwise).

Any of these combinations would be okay for testing an animal in which there’s suspicion of H5N1 flu exposure / infection, but I’d rather have a quick H5N1-specific result in these cases, and I’d want to make sure that the lab will forward any positive sample for further genomic testing, so we can better understand the situation with H5N1 flu. 

Take home message

  • Talk to your lab to know what they can (and can’t) do in terms of testing for H5N1 flu, and follow up testing.
  • We can’t just stop at “flu positive.” Any such result needs to be scrutinized to make sure we know the strain (or strains) involved.
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TLDR: Nope.

These days I commonly get the question ”Does vaccination of dogs with available canine influenza vaccines protect them from H5N1 avian flu?” While we don’t have any hard data on this, we still have a pretty good idea of the answer.

One of the challenges with flu vaccination (in any species, including humans) is the lack of good cross protection between strains (e.g. H3N2 vs H1N1 vs H5N1). In general, we assume there’s little to no cross-protection, and organizations such as CDC, Public Health Agency of Canada and WHO have stated that seasonal flu vaccines don’t offer any protection to people against H5N1 flu. 

That said, theoretically there there may be a bit of protection, though it’s hard to have confidence in that based on data from older lab animal studies. One study (Rockman et al. J Virol 2013) showed that ferrets vaccinated with human seasonal flu vaccine had partial protection against challenge with H5N1 flu. They determined that this was from the H1N1 component of the vaccine, and was predominantly from the neuraminidase (N) part (H5N1 and H1N1 have the same N1). While we typically pay more attention to the H component for vaccination, the similarity in N may be useful. That means there may be some protection of people from H5N1 flu if they’re vaccinated for seasonal flu, but not a lot, and we have to be careful extrapolating too much from older studies using different types of H5N1 in lab animal models. 

Canine flu vaccines target H3N2 canine flu, plus or minus H3N8 canine flu strain. (Realistically we only care about H3N2 now, since H3N8 appears to have disappeared as of a few years ago.) Those are quite different from H5N1 avian flu in flu terms.  Since there’s no overlap in the Hs or Ns, we wouldn’t expect to even have that small theoretical cross-protection benefit. If we had an H1N1 canine flu strain, maybe there’d be some protection, but (thankfully!) we don’t.

Does canine flu vaccination help protect against flu recombination? 

Recombination (mixing) of different flu strains in the same host (human or animal) to create a new, more problematic strain is certainly a concern. We don’t want someone to be infected with seasonal flu and H5N1 flu at the same time, as that creates the potential for a new flu strain to emerge that has the hallmarks of a human flu (readily infected people, effective human-to-human transmission) but has picked up enough H5N1 bits that we don’t have protection from previous exposure or vaccination and may can cause more severe disease. So even though seasonal flu vaccines in people don’t protect against H5N1 flu, there is still benefit from reducing the human seasonal flu burden, as it in turn reduces the risk that a person will be infected with multiple flu strains at the same time, which reduces the chances of recombination.

Does the same principle apply to vaccination of dogs against canine flu? It’s a stretch. There could be some potential benefits for canine health, but probably not much benefit for public health. Canine flu is much rarer than seasonal flu is in people, so there’s less potential benefit simply because there’s less disease to prevent. There’s also less baseline protection against canine flu in dogs because it’s rare and therefore vaccination is uncommon. So from a disease transmission standpoint for dogs, a new flu strain against which they don’t have immunity isn’t that different from the current H3N2 canine flu strain, since most dogs don’t have immunity to that either.

However, there could potentially be a difference in terms of disease severity. Fatal H5N1 infections have occurred in many mammals and at least one dog, and we don’t want an H3N2/H5N1 recombinant virus that spreads nicely dog-to-dog and is more likely to cause severe disease.  The odds of that happening are extremely low, but not zero.

Also bear in mind that canine flu vaccines aim to reduce the severity of disease more than prevent infection altogether. That still might be useful, as a mildly affected dog with some degree of immunity might have a lower H3N2 viral burden, but it’s hard to say how much that would really help protect against recombination of flu viruses, even if we had more widespread vaccination in the dog population. Probably not too much.

Public health benefits would be less of a reason to promote vaccination of dogs against canine flu stains. Canine H3N2 flu poses little risk of infection of people, so a hybrid of canine H3N2 and H5N1 wouldn’t be expected to be more transmissible to people (even though it would potentially add some mammalian adaptations to an H5N1-related virus, which is definitely not the direction we want the virus to go). For dogs to be a flu “mixing vessel” of public health concern, a human flu strain would need to be involved. While dogs can occasionally be infected with human flu strains, the odds of a dog having H3N2, human seasonal flu and H5N1 at the same time are pretty low. Even then, whether or not the dog was vaccinated against H3N2 wouldn’t really affect the risk, since we’d be primarily concerned about the human flu and the H5N1 flu mixing in the dog, not whether or not H3N2 joins the party.

Should we change how we approach canine flu vaccination?

I’d mostly stick with our current approach, which is based on assessment of the risk of exposure of the dog to canine flu, and the risk of serious consequences should the dog get flu (e.g. elderly, brachycephalic, underlying heart or respiratory disease). Since there are some plausible dog health concerns about H3N2/H5N1 recombinants, I’d drop my threshold for vaccination in dogs that also have a higher risk of exposure to wild birds (or dairy farms in the US). Dogs that have a reasonable risk of exposure to both types of flu virus (canine and avian) would be higher on my list to vaccinate, but that’s a very small subset (currently), and the benefits of vaccination beyond H3N2 protection are probably very limited.

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Issues with raw diets and H5N1 influenza risk in cats (and dogs) have gotten a lot of attention in the last week or two. Like most emerging disease situations, it’s still fluid, and we’re learning more as time goes on, but we know enough at this point to at least make some basic assessments and recommendations. Here’s my current take on it.

What are the concerns with H5N1 influenza and raw diets for pets?

The unprecedented pandemic of H5N1 highly pathogenic avian influenza (HPAI) has ongoing for more than 2 years. Massive numbers of wild birds have been affected around the world. Spillover into domestic animals is an ever-present risk where this virus is circulating in wild birds, with domestic poultry being the most severely affected. Millions of domestic poultry have died or been depopulated due to infection, and spillover infections have also occurred in mammals, including many cats and at least one dog.

Recently, H5N1 influenza infection has been linked to consumption of contaminated raw meat diets in at least two cats. It’s been well established for some time that ingestion of infected birds can lead to H5N1 influenza infection in cats, based on earlier studies and field observations. It is therefore unsurprising that infections could occur if infected poultry makes its way into raw diets fed to cats, and unfortunately the infection in cats is often fatal.  The risk to dogs is less clear, but infection was reported in one dog that died shortly after close contact (chewing on) an infected bird. Dogs may be less susceptible to H5N1 influenza than cats, but they are still susceptible and infection can have dire consequences, so the same concepts apply to both species.

What types of raw diets for pets pose a risk of H5N1 influenza infection?

Poultry-based diets are the main concern, including chicken, turkey and duck, as all poultry are highly susceptible to H5N1 influenza. However, the virus is now also widespread in dairy cattle in the US, particularly in certain states (like California at the moment). Work done by the Food Safety and Inspection Service (FSIS) in the US has found no evidence of virus in retail beef samples and only very low levels of virus in samples from 1 of 185 cull dairy cows tested (the positive cow did not enter the food chain). More investigation is needed, but it is likely that viral loads in muscle of infected cattle are far less than those in poultry. Risks from beef are presumably low, but the potential for the virus to be present in meat from infected dairy cattle cannot be dismissed.

Does use of “human grade” meat in raw diets eliminate the risk?

Human grade meat does not mean pathogen-free – it only means that the meat would have been allowed for sale for human consumption based on more rigourous requirements for the animals, facilities, processing and handling. These presumably reduce, but do not eliminate,  the risk of H5N1 infected animals entering the pet food chain.  

Does high-pressure pasteurization of raw diets eliminate H5N1 influenza virus?

High pressure pasteurization (HPP) of food products uses high pressure (rather than high heat, as in cooking) to reduce contamination with bacteria and viruses. Many commercial raw diets for pets are high pressure pasteurized (which is good). The pressures achieved during this process should inactivate influenza virus, but there are no standard methods for HPP. The effectiveness of HPP depends on the pressure, temperature, and composition of the food matrix. It is unclear whether manufacturers have developed and validated the method for their wide range of diets and pathogen risks. Recalls of high-pressure pasteurized raw diets because of Salmonella contamination have been regular occurrences, and a recent infection in a cat was linked to such a diet. High pressure pasteurization should be considered a risk reduction step, not a risk elimination step.

Are frozen or freeze-dried raw diets lower risk for H5N1 influenza?

Freezing and freeze drying are effective preservation methods for viruses, so its unlikely that these methods substantially reduce the risk of viral contamination in raw diets. Ultralow freezing is used for longterm preservation of viruses, but shorter-term survival is also possible at temperatures achieved using normal freezers (-20C). A study of the survivability of H7N9 influenza on raw chicken meat (Dai et al. Lancet 2022) reported that viral infectivity was maintained for 9 days at -20C, 4 days at 4C and 4 days at 25C. This was a rather small study, so it is possible that somewhat longer survival could occur in some situations. In nature, long term (e.g. overwintering) survival of influenza virus in ice has been suspected.

While the survival kinetics of this virus with freezing are not clear, it should be assumed that the virus could survive frozen for at least a week, and possibly much longer. Freezing should not be assumed to be a risk mitigation measure for viral contamination of raw diets.

Freeze drying is a highly effective virus preservation method. Survival of virus in freeze dried food has not been assessed, but in the absence of specific evidence, it is reasonable to assume that influenza virus would survive for long periods of time in such diets.

My cat is doing well on a raw diet and I don’t want to change. What can I do?

Raw diets can be cooked so that the cat receives a diet with the same ingredients but without the risk from H5N1 influenza (and other pathogens). There is no evidence that cooking reduces the health benefits of a diet. Cooking the food to an internal temperature of 165F/74C will inactivate influenza virus and other pathogens such as Salmonella.  

My cat has eaten a raw diet that’s been recalled diet. What should I do?

You should observe your cat closely and contact your veterinarian in you are concerned or your cat develops any signs of illness. Antiviral prophylaxis could be considered in particularly high-risk situations where it is likely that the cat has eaten contaminated food. This may not be the case for all recalled diets and would depend on the nature of the recall. Early signs of H5N1 influenza in cats are not well established, but often seem to be vague signs such as lethargy, malaise and decreased appetite. Rapid progression to severe disease can occur so veterinary care should be sought as soon as possible.

My cat has eaten a raw diet that’s not been recalled. What should I do?

Unless there is evidence that the diet has been implicated in disease, the odds of a problem developing are low. However, it would still be ideal to transition the cat to a cooked diet, whether that’s a commercial wet or dry diet, a home-cooked diet or cooking the cat’s current raw diet. Monitoring of your cat for illness, as above, is still indicated, as always.

What are risks to people from contact with contaminated raw diets?

The risk to people from H5N1 influenza from handling contaminated raw diets is likely quite low but not zero. Exposure could happen from inadvertent ingestion of the virus from contaminated surfaces (e.g. food prep surfaces, refrigerator, food bowls). That would likely be low level exposure, but the infectious dose of the virus is not known so it could still be relevant. There are similar risks with these diets from pathogens such as Salmonella, so good food handling practices are always warranted. These include avoiding cross-contamination with human foods and kitchen surfaces, careful cleaning and disinfection of in contact surfaces, dishes and utensils, and thorough handwashing (or use of an alcohol-based hand sanitizer) after contact with the raw diet or food bowls.

The greatest risk to people would be from exposure to a cat (or less likely a dog) infected with H5N1 influenza. An infected animal might be shedding enough virus to infect people, although the risk of this is still unclear. Any cat or dog with suspected influenza should be handled sparingly, and with use of good infection control measures, including a mask (ideally an N95 respirator) and eye protection.  

Closing thoughts

My opinions on raw diets have been pretty clear all along. I don’t think there’s any evidence that raw diets have any health benefits over an appropriate cooked diet, but raw diets come with numerous infectious disease risks. I’ve seen enough dogs and cats (and sometimes owners) sickened from raw diets to be confident in that. At the same time, I’m a realist and know that some people will continue to feed pets raw diets regardless. That’s why we have a infosheet about raw diets that includes ways to reduce the infectious disease risks for those who choose to feed them to their pets.

The current situation doesn’t really change anything for me. I’m still opposed to raw diets for pets, and this simply adds yet another layer of risk to pets and people that consume/feed them.

If someone is adamant that they are going to feed their pet a raw diet, here’s what I currently recommend:

  • Avoid diets that contain poultry (including duck)
  • Use a diet treated with high pressure pasteurization (realizing it reduces risk, but does not eliminate it)
  • Take care to avoid cross contamination of human food, and use good food handling and hygiene practices (always)
  • If your pet has been fed raw meat and gets sick, make sure your veterinarian knows about the diet so they can consider whether that might be relevant
  • Pay attention to the news and recalls so that you can stop feeding a diet if there are any known issues (but realize that we don’t typically know about any issues until one or more animals gets really sick or dies from the diet)