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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)
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Hot on the heels of the recent death of a cat in Oregon due to H5N1 influenza infection linked to a raw diet (that some raw diet proponents are trying to deflect or downplay), we have confirmation of a very similar case in California. Los Angeles County Public Health has issued a notice to avoid feeding Monarch Raw Pet Food “due to detection of H5 bird flu in product samples.” (note the plural). H5N1 was confirmed in one cat that was fed this diet and is suspected in four other cats from the same household.

The diet type was not reported, but the company’s website indicates “Our pet food is made of human grade USDA free-range poultry that is raised in the San Joaquin Valley.” Free range poultry are at increased risk of H5N1 infection from wild birds. Nonetheless, it would be interesting to know how infected poultry made it into the food chain (even the pet food chain), since H5N1 influenza usually causes widespread illness and death in domestic poultry, so it’s pretty obvious when it hits a poultry farm (and sick birds cannot be sent to slaughter).

The status of the infected cat wasn’t reported, but H5N1 infection in cats is often fatal based on what we know to date. Hopefully the cat had a milder infection, but I assume it was at least worse than a routine upper respiratory tract infection, since testing is usually limited to pets that are pretty sick.

The good news is that food-associated H5N1 influenza risks are totally avoidable… just don’t feed pets raw diets. The cost:benefit calculus is pretty easy since this virus kills cats and there are no health benefits of raw diets. More information about raw meat-based diets for pets (beyond the risk of H5N1 flu) can be found in the Worms & Germs / OAHN Raw Meat Diets infosheet, available on the Worms & Germs Resources – Pets page.

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The Oregon Department of Health has issued a warning to pet owners about contaminated raw pet food after H5N1 avian influenza virus was detected in turkey-based raw (and frozen raw) pet food from Morasch Meats. Testing was performed after the death of an indoor cat from H5N1 flu in Washington County, Oregon. The virus from the cat and from the pet food were a genetic match, making a solid link between the two. The pet food company is voluntarily recalling some of their Northwest Naturals diets.

This highlights (yet another) risk posed by poultry-based raw pet food at the moment in areas like the US where H5N1 flu is actively circulating. There could also potentially be risk of H5N1 contamination of raw pet food made with beef, if the meat came from infected US dairy cattle. Risks could also extend to other raw pet food formulations if there is cross-contamination from these higher-risk ingredients.

There are no health benefits to raw diets beyond a properly formulated cooked (be it commerical or homemade) diet. H5N1 flu is now yet another potential threat to animals fed raw diets. The risk may extend to owners as well, through exposure to virus from handling food, and potentially from infected pets (especially cats, but we still don’t know the level of cat-to-human transmission risk).

We have seen foodborne H5N1 influenza infection in cats in multiple situations, often resulting in fatal disease. Foodborne disease probably helps explain some of the earlier reports of H5N1 in indoor cats, and in that respect it’s good to have an idea of how all these infections are occurring. The more infections we can’t explain, the more we worry about serious issues like unknown human (owner) infections with subsequent human-to-cat transmission. I’d much rather be able to attribute cases to straightforward food-associated transmission than have to explore other transmission pathways, or think that there may be silent human-associated spread.

The mitigation approach here is simple: just avoid raw pet food diets (especially poultry-based diets).

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There’s a reason we pasteurize milk: there’s always a risk of contamination of raw milk with infectious agents, and pasteurization is a cheap, easy and effective way to mitigate disease risks from drinking milk and other dairy products. There are no clear benefits to raw milk (despite what some may say) and the risks from drinking raw milk are clear (and have been known for decades).

However, raw (unpasteurized) milk can still be legally sold in some states in the US (it is not allowed in Ontario). It’s getting more attention as a certain high-profile US politician talks about raw milk alongside his anti-[lots of things] agenda. That’s a huge concern for human health. There are some animal health issues too, and since that’s my turf, I’ll talk about those.

A recent report from LA County highlights the risk of H5N1 influenza in raw milk from infected cows in California (where hundreds of herd have been affected since the summer). So far, this seems to just be a problem in the US, as they are the only country where H5N1 flu has spread to (and between) dairy cattle. Lack of an aggressive initial response, in combination with how dairy cattle are managed and moved across the US, led to widespread infections on dairy farms in certain states. The strain of H5N1 flu affected the cattle has a unique predilection for the bovine udder. Infected cattle shed huge amounts of virus in their milk, and milk (and milking equipment) therefore seems to be the main source of transmission from and between cattle.

Milk from infected cattle shouldn’t enter the food chain, but not all infected cattle are identified right away. Pasteurization will effectively inactive influenza virus, so pasteurized milk is safe regardless. The concern is with consumption raw milk (whether it is sold legally or illegally, depending on the jurisdiction).

The LA County Department of Public Health has reported the deaths of two cats from H5 influenza (that will almost certainly be confirmed as H5N1 when all the testing is completed). Both cats had consumed recalled (contaminated) raw milk, and had what seems to be a typical disease course for cats with this virus. They had some initial non-specific signs (e.g. loss of appetite, fever) then developed severe, progressive and ultimately fatal neurological disease. Presumably public health is closely monitoring the people and other animals in the household.

They are also investigating three other feline cases from a different household. One initially tested positive for influenza already, so it’s pretty safe to assume this is another H5N1 cluster. Two cats in that household died “after worsening respiratory illness.” More details about that would be nice since we still don’t have a good handle on the scope of disease that occurs in cats and dogs, but it would help us to better flag potential flu cases. There’s no known link to raw milk for these three cats yet, but they are investigating potential sources of exposure, including raw milk.

Almost certainly they are trying to sequence the virus from these cases.

  • They’ll presumably find the dairy-associated strain of H5N1 in the first household; that would make a solid link to the raw milk as the source.
  • Sequencing from the other household will be important to help sort out potential sources (e.g. dairy strain vs strains in wild birds in the area).

While avoiding raw milk doesn’t eliminate all H5N1 flu risks (since infected birds are still a source), it’s a completely avoidable risk factor. There are no health benefits from raw milk, but there are very clear risks (which now include influenza as well). The cost:benefit calculus is pretty straightforward here.

What about risks from raw milk in areas outside the US where there’s no known H5N1 flu in dairy cattle?

There are still other infectious disease risks from raw milk. Also, just because we don’t know that there are cases now doesn’t mean that there are actually none or that there will be none forever.

It’s pretty simple to me: just avoid drinking raw milk (and other unpasteurized dairy products), but remember that pasteurized milk and dairy products are safe!

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In some ways, I wonder why there even are recalls for raw pet foods and Salmonella. We know contamination is common, and the contaminated foods that get identified and recalled are presumably a very small portion of the amount of contaminated food that’s in circulation. At the same time, when a problem is identified and the FDA asks for a recall, I find it astounding that a company would ignore that.

Darwin’s Natural Pet Products is in the news yet again for selling contaminated raw pet food – and ignoring an FDA request for a recall.

As a result, the FDA has issued a public notice regarding Darwin’s Natural Selections Pet Food:

  • The U.S. Food and Drug Administration is cautioning pet owners that FDA samples of five Darwin’s Natural Pet Products raw cat and dog food made by Arrow Reliance, Inc. tested positive for Salmonella and a sixth FDA sample tested positive for Salmonella and Listeria monocytogenes (L. mono). 
  • The FDA recommended that Arrow Reliance, Inc. recall all six lots of product. To date, the firm has not recalled the affected products and could continue to distribute them. Therefore, FDA advises consumers to keep checking Darwin’s Natural Selection Antibiotic & Grain-Free products for the affected lot numbers prior to feeding to pets.

I could make a crack about Darwin’s “natural selection” but would rather the company just be responsible, recall their products and review their practices, to reduce the human and animal health risks.

Cleaning up some of the misinformation on their website would be good too, like where it suggests Salmonella is only a risk to puppies and kittens less than 4 months of age, or to those that are immunocompromised. Salmonella can most definitely cause disease in healthy adult dogs and cats, as well as their owners.

For more information about raw diets, including the risks and how to reduce them, see our recently updated Raw Meat Diets infosheet (produced in collaboration with OAHN) on the Worms & Germs Resources -Pets page.

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A recent recall of a raw pet food diets in the US due to contamination with Listeria monocytogenes has sparked some concern about the risks to people (and pets) that might have been exposed to these products.

In some ways, the big concerns raised by the recall are misplaced, not because it’s not an issue, but because a large percentage of raw diets are contaminated with pathogenic microorganisms, but most raw food isn’t tested for them. So, this is not likely a rare scenario, it’s just one that we found out about.

It’s not clear what (small) percentage of commercial raw diets actually are tested and how (since when a company doesn’t really want to find anything, they would tend to use methods that don’t look too hard). In this case, “The issue was discovered during a facility inspection conducted by the U.S. Food and Drug Administration (FDA) and The North Carolina Department of Agriculture (NCDA).” It’s not reported whether they identified issues with the facility and processes that triggered the inspection, or if they just collected samples for testing during a more routine visit.

That’s not to say Listeria in raw pet food isn’t a concern. It certainly is, but this recall has only flagged a small number of contaminated raw pet food products.

If we look at past studies of raw pet food, we know that finding bacteria like Salmonella, Listeria and E. coli (including multidrug-resistant strains) is common. A large FDA study in 2014 found Listeria in 16% (32/196) raw pet food samples, but in no dry pet food diets. So it’s totally unsurprising to find this bacterium (and others) in raw diets. It’s actually surprising to me that they bother to recall these diets at all, since it should be assumed that all raw diets that don’t undergo a pathogen reduction step (like high pressure pasteurization) are contaminated with pathogenic organisms. We expect these to be contaminated, whether they’re bought at the grocery store or a pet store. (That’s why we are supposed to cook raw meat and use good food handling practices for human food as well… since we often don’t do those well, it’s also why people end up barfing a lot).

What are the health risks from these diets contaminated with Listeria?

Risks to people

Listeria is certainly a concern in people, especially those who are elderly or pregnant. It can cause serious foodborne infection and outbreaks. In the US, approximately 1600 people get listeriosis every year, and about 260 of those people die from the infection. That’s not a huge number of infections, but that proportion of serious illness and death means we pay attention to it.

I’ve never seen a human infection with Listeria linked to raw pet food, but it’s certainly plausible that it could occur. The risk is probably pretty low, since infection would require ingestion of the bacterium from raw pet food, but given how poorly we often handle food (human or pet) and the potential for cross-contamination with human food, we can’t dismiss the potential, particularly in household with high-risk individuals.

Risk to pets

Listeria can cause disease in dogs and cats, but it’s quite rare since both species are fairly resistant to infection. The health risk to an average, adult, otherwise healthy dog or cat is going to be really low. Risks are probably highest in older dogs or cats, and in pregnant animals.

What should be done if someone has purchased a recalled diet?

Overall, the risks to people in most households are low. The problem is inadvertent ingestion of Listeria from contaminated hands, contact with the dog’s face after it eats or cross-contamination of human food. Listeria exposure is also a concern through consumption of some human foods (classically deli meat) so we have think about this raw food exposure alongside the broader ecosystem of exposures that we have.

The FDA recommends: “If you find that you have products from Lot 21244, please contact Viva Raw at info@vivarawpets.com for a refund on any remaining product—you should then destroy the food in a way that children, pets, and wildlife cannot access. Do not feed the recalled product to pets or any other animals. FDA recommends humans do not touch the contaminated food product with bare hands. While wearing gloves or using paper towels, place the contaminated food in a sealed plastic bag and throw it in the garbage. Areas that may have come in contact with the contaminated product should be sanitized. Do not sell or donate the recalled products.”

For pets

If a dog or cat has eaten a recalled diet but still looks healthy, don’t worry. Testing a healthy pet that has eaten one of these diets is not something I’d recommend.

For people

“Talk to your physician if you’re concerned” is always the default answer, but realistically it’s very unlikely anything would be done for a person who is healthy. However, if someone is sick and has had contact with the recalled diet (or any raw diet), they should make sure their healthcare provider knows about the potential exposure to Listeria and other nasty bacteria.

Take home messages:

Feeding raw diets to pets carries inherent risks to pets as well as people.

Risks are greatest to individuals (animal or human) who are immunocompromised, elderly, very young or pregnant, so raw diet feeding in household with those individuals poses extra risks.

Raw diets are best avoided since there’s no evidence they are superior to cooked diets. However, if someone really wants to feed a raw diet anyway, those treated with high pressure pasteurization (HPP) are presumably lower risk, because HPP reduces (though does not necessarily eliminate) pathogenic bacteria in the food.

If a raw diet is fed, basic food handling and hygiene practices are the key, focusing on the food, the food bowl, any areas that the food contacts, and the pet’s feces. More information about raw diets and risk reduction can be found on the Worms & Germs Resources – Pets page, including our recently updated infosheet on raw diets done in collaboration with the Ontario Animal Health Network.

I’m supposed to be in Rome for an antimicrobial resistance (AMR) meeting but a positive COVID test but a kink in my travel plans. So, I’ll take some unexpected time to catch up on some blog material. We’ll start with a pair of pet-food-linked Salmonella outbreaks, starting with a Canadian outbreak.

The Public Health Agency of Canada has issued a notice about an ongoing outbreak of extensively drug resistant (XDR) Salmonella I 4,[5],12:i:-infection. XDR Salmonella is a big concern because it’s resistant to a large number of antibiotics, including all those that are commonly recommended for treatment, when needed (i.e. ceftriaxone, azithromycin, trimethoprim/sulfamethoxazole, ampicillin, and ciprofloxacin), plus other drugs like aminoglycosides, chloramphenicol, and tetracycline.  While resistant Salmonella aren’t inherently more likely to cause severe disease than susceptible strains, and a lot of infections resolve without specific treatment or antibiotics, if someone is sick enough that they need antibiotics and the initial drugs don’t work because of resistance, that can lead to a greater risk of severe disease or death.

Here’s a quick synopsis of the investigation to date:

  • 40 cases have been identified, but presumably the actual number is much higher since only a small fraction of people with salmonellosis actually go to a doctor and get tested.
  • Most of the cases have been found in Quebec (21), followed by Ontario (14) and Nova Scotia (2), with single cases from New Brunswick, PEI and Manitoba.
  • To date, infections identified occurred between July 2020 and September 2023, but the investigation (and presumably the outbreak) is ongoing (see epidemiological graph below).
  • Thirteen (33%) of identified cases were hospitalized (that’s a pretty high rate), but fortunately no deaths were reported.
  • As is typical, young children bore the brunt of disease, with 43% of cases being children 5 years of age or younger.

Finding the source of an outbreak like this is often a challenge. It’s much simpler when it’s a nice, discreet outbreak in one town that’s quickly linked back to a single event, restaurant or food type. It’s harder when it’s an outbreak that involves numerous provinces and years, and when a lot of time has passed before the problem is identified. The investigation of this outbreak has identified links to contact with raw pet food diets (or dogs fed raw food diets) and contact with cattle, both of which make sense since they are well established risk factors for salmonellosis.

The outbreak strain was found in raw pet food from the home of a sick person. The notice indicates that “A single common supplier of raw pet food has not been identified.” It can be difficult to confirm the contamination of the pet food itself, because these investigations usually start well after infection is identified (especially in early cases), and it takes time to identify an outbreak and potential common sources. So, by the time we’re concerned about raw diets, the source food is usually long gone.

There’s also a statement that dogs and cattle have been infected and died. Some raw diet proponents continue to push false information that Salmonella doesn’t affect dogs. We know it does in some cases, and infection can kill animals too, so this is another reminder of that.

What does this change?

Not much. It’s more of a reminder of the issues about antimicrobial resistance (AMR) in animals and humans, the need to better understand the scope and impact of resistance, and the potential risks from raw food diets for pets. It’s also another reminder of the need to reduce AMR in livestock, which is a key issue here. Whether the infections came directly from cattle or indirectly from beef, it all started off with resistance in a Salmonella strain originating from cattle somewhere. We need to continue to try to find ways to reduce the incidence and impact of AMR across all species (including humans), as we are ultimately all interconnected.

My line about raw diets is that I’d rather they not be fed to pets at all, because the risks outweigh the benefits from my perspective. However, I realize it’s still going to be done, so I focus on trying to get people to avoid raw feeding in high risk households (e.g. those with young kids, elderly individuals, pregnant women and people with compromised immune systems), and making sure that people who feed raw diets take basic measures to reduce the risk to them and their pets. More information about raw diets and their associated risks (and how to mitigate them) is available on the Worms & Germs Resources – Pets page. The US CDC also recommends against feeding raw diets to pets. They also have some good resources on their website including an infographic for pet owners about raw diets.

Avian flu caused an uptick in discussion about health risks associated with feeding dogs and cats raw meat, based on the possible (and still pretty tenuous) link between raw poultry and a large number of H5N1 infections in cats in Poland.

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The link between raw diets and flu infections is new, and something we need to look at more, but since common things occur commonly, we need to also pay attention to the traditional concerns with raw diets. A recent report from Quebec about multidrug-resistant Salmonella infections in people highlights one of the major human health risks of raw pet foods. Salmonella contamination of raw diets is common, and this bacterium can cause disease in both people and animals.

The report was based on an investigation of 15 human infections with a multidrug-resistant Salmonella enterica serotype 4,[5],12:i:- (not all Salmonella serotypes have specific – or pronouncible – names).

  • The 15 infections were identified by 10 different health regions in Quebec between July 2020 and December 2022. They then found 2 more cases in Dec 2022.
  • As is typical, kids bore the brunt of the problem. Nine of cases were in kids less than two years of age.
  • The bacterium was resistant to a variety of antibiotics, including ampicillin, cefotaxime, ceftriaxone and trimethoprim sulfa, and resistant or of intermediate susceptibility to fluoroquinolones and azithromycin. That’s pretty concerning, because if you end up in hospital with salmonellosis, those are all the typical go-to drugs for initial treatment. If someone is seriously ill with Salmonella and is started on one of those drugs pending culture results, the treatment won’t work and they’ll get sicker or potentially develop more complications before an effective treatment is identified.

As is typical, when the investigation started, they asked questions about the common sources of Salmonella. Initial results indicated some patients had contact with cattle farms and some with raw pet foods. This led to a more detailed investigation, and then they found that 14 of 17 people had contact with raw pet foods.  The same bacterium was also found in 2 dogs that were fed these raw diets, further supporting the link to pet food.

The report also briefly mentions 10 cases in Ontario with the same strain, at least 2 of which had contact with raw diets.

This doesn’t really change anything, since we already know that animal and human infections occur from exposure to raw animal-based pet diets. It’s important information to get out, though, because there is a still a general lack of awareness of these risks and lots of misinformation. Some manufacturers take steps to reduce (not eliminate) the risk of bacterial contamination in their raw diets (mainly high pressure pasteurization). Some try to explain the risks and how to reduce them (if you’re going to feed a raw diet, use those companies). Some do nothing, and worst of all some downplay the risks and even provide false information.

My typical take home messages for people thinking about feeding raw diets are:

  • There is risk to people and animals.
  • The risk can be reduced a lot with common sense, but not eliminated.
  • The risk is probably low with common sense and in a low risk household.
  • The risk is unacceptably high in households with high risk people (e.g. young kids, elderly, pregnant, immunocompromised individuals) and high risk dogs (similar groups).
  • If you want to feed a raw diet, use some basic precautions to reduce the risks. We have more on that in our Raw Meat Infosheet available on the Worms & Germs Resources – Pets page.

People can get pretty fired up when I talk about raw diets for pets. I’ll start off with my personal bias: I’d rather not see pets fed raw meat and raw animal-based products (e.g. pig ears and various bits-o-cow you can find in pet stores). There are clear risks to pets and owners from raw diets, including infectious and non-infectious issues. I’ll stay in my lane and focus on the infectious disease topics here.

We, and others, have shown that pets fed raw diets have high rates of shedding of certain bacteria that can cause disease.  I’ve been involved in various investigations of disease in dogs and cats (and some in owners) linked to raw diets for pets. At the same time, I’m a realist and recognize that the risk isn’t overwhelming for most people and pets, and not everyone is going to change their pet’s diet as a result of said risk.

So, I approach raw diets from the standpoint of “I’d rather not see them used, and there are almost always acceptable, lower risk commercial cooked diets available” but at the same time “The risk is probably low for most dogs and owners, but some situations are clearly higher risk.” I’d rather spend my energy focusing on situations where I think it’s a really bad idea, and try to give some guidance to people that insist on doing it. That way I can still engage people, rather than push them away with a more dogmatic approach.  That’s why we created a factsheet for pet owners about raw diets (to be honest it needs an update, but it’s still useful as many of the risks themselves haven’t changed… but more on that below).

We have to keep our eye on this issue and be alert for new information that changes the story in any direction.  Initial work on raw diets focused on Salmonella, and that’s still an issue.  However, in the past few years, my bigger concern has been antibiotic-resistant bacteria like E. coli. Dogs fed raw diets have much higher rates of shedding of multidrug-resistant Gram negative bacteria like E. coli in feces. Eating a raw diet seems to be as much of a risk factor as the dog being treated with antibiotics (probably because antibiotic treatments are short term while feeding is much longer term exposure). What this means for human or animal health isn’t clear, but raw pet food-associated infections have been identified in people and a dog carrying a resistant bacterium in its gut is likely at increased risk of developing an infection with that bacterium. For E. coli and related bugs, urinary tract infections would be among the most common issues, but a wide range of disease can potentially occur.

That’s a long introduction to the paper that prompted this post. The study in question (Mounsey et al, One Health 2022) doesn’t change the story at all, but adds more pieces of evidence.

In this study, they collected history and fecal samples from puppies at 16 weeks of age. Those samples were tested for antimicrobial-resistant E coli.

  • They ended up recruiting 223 puppies, 43 of which were being fed a raw diet.
  • 32 (74%!) of the raw-fed puppies were shedding E. coli resistant to at least one antibiotic, compared to 76/180 (42%) of the other puppies.
  • They looked at a number of other potentially contributing factors, such as where the dogs were walked, and didn’t find anything else that was associated with resistant E. coli shedding.
  • When they looked at resistance to individual antibiotics, raw diet feeding was associated with resistance to many drugs, with the strongest effect for fluoroquinolones, a drug class classified in the highest priority critically important antimicrobial group for humans.
  • When they looked more at the fluoroquinolone-resistant isolates, they found that many were strains that were found in urinary tract infections in people in the same area.

So, I’ll stick with my “I’d rather not have people feed their pets raw diets” line, with the added “I  REALLY don’t want to see those diets fed to very young pets, old pets or pets with immunodeficiencies, OR in households where someone is very young, elderly, pregnant or immunocompromised.”

If someone’s intent on feeding a raw diet, risk reduction is the key (risk elimination being impossible).

Diet selection is part of that. Some diets are treated to reduce (not eliminate) microbial contaminants, usually using high pressure pasteurization, which applies pressure to kill bacteria and parasites in the product. It’s not perfect by any means, but it’s useful in decreasing the microbial load. Sticking with companies that provide information about their quality control and risk reduction plan is good too. Some raw diet companies do a good job. Others… well, not so much.

Beyond that, it’s a lot of good ol’ common sense, hygiene and hand washing. Our raw diet factsheet has some information, and any good food safety infosheet will have a lot of tips that apply equally to handling raw diets for pets as they do to handling raw products during food preparation for people.

I’ve written a lot about raw pet food in the past. Initially, the concerns were about Salmonella, since raw-fed dogs and cats have high rates of shedding Salmonella, and both pets and owners can get sick from it (owners can be infected directly by the pet or from handling or cross-contamination from the pet food… it’s always hard to sort that out).

More recently, I’ve been concerned about multidrug-resistant E. coli and related bacteria in raw pet diets. I think this may now be a much bigger but insidious risk. Eating a raw diet has been shown in a few studies to be a major risk factor for fecal shedding of highly antibiotic-resistant bacteria in pets, particularly extended spectrum beta-lactamase (ESBL) producing bugs.

There are other facets to this problem as well. A recent paper in the journal Epidemiology and Infection (Kaindama et al, 2021) describes a cluster of human E. coli O157 infections in the UK that were linked to raw pet food. This strain of E. coli can cause serious illness in people, including hemolytic uremic syndrome, which can be fatal. The bacterium can be found in the intestines of food animals (mainly cattle) and can therefore sometimes contaminate meat, or vegetables fertilized with manure.

In this cluster, 4 people infected by a similar strain of E. coli O157 were identified.

  • All 4 patients got sick within a one-month period in 2017.
  • I’m guessing three were 6-year-old children, based on the median and age range provided in the paper. The burden of zoonotic diseases often falls disproportionately on kids.
  • Three of the patients were hospitalized, and one died.

During the investigation, no typical sources of E. coli O157 exposure were identified. The only commonalities between cases were all had contact with dogs, and a history of consuming raw carrots. Three of the patients had been exposed to dogs fed a raw meat diet, two of which had received tripe from the same supplier. The other person’s dog was not fed a raw meat diet but had contact with another dog that was fed raw meat.

E. coli O157 was subsequently found in raw pet food samples from the affected households, but they were different strains. That’s not too surprising, since contamination of the pet food would be variable, and testing would have occurred well after the food that likely caused the infection was fed. One batch might be contaminated, the next not and the next contaminated with a different strain. Finding different strains doesn’t round out the story as nicely, but it highlights other concerns. This wasn’t a one-time point exposure cause by some unusual event. Contamination of raw pet food with this concerning bacterium might be more common than has been previously recognized.

Whether these are rare cases or a small subset of actual cases is unclear. This cluster was identified because:

  • The infections occurred close together in time (within 1 month)
  • Public Health England does detailed whole genome sequence testing of E. coli O157 isolates
  • They have detailed case questionnaires
  • They looked for and found a link

Large outbreaks of disease in people involving the same E. coli O157 strain wouldn’t be expected from exposure to dogs fed diets where there’s probably a lot of small batches of the pet food produced and batch-to-batch variation with regard to contamination. Patterns need to be apparent to flag a potential problem, and sporadic cases aren’t as amenable to that. So, we don’t know if this was an exceptional event (i.e. infections are rare) or whether this was a matter of the right circumstances allowing for rare diagnosis of a more common problem.

My personal opinion here is based on seeing enough sick pets and sick people from raw diets. For that reason, I don’t like to see these diets fed. That’s particularly true in households with people or animals that are at higher risk of severe disease (i.e. young, old, pregnant, immunocompromised). If someone is going to feed a raw diet anyway, there are ways to reduce the risk to people and animals, both in terms of products that are purchased (e.g. high pressure pasteurization likely reduces the risk a lot, even though it doesn’t eliminate it) and how raw diets are handled in the home. More information about feeding raw diets and reducing the risk is available on the Worms & Germs Resources – Pets page.