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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)

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.

Back in 2008, we reported an association between feeding raw diets to dogs and shedding of cephalosporin-resistant bacteria in dogs (that makes me feel old… one of many things that does these days, I guess). It didn’t get too much attention at the time, since the main focus of the study was on Salmonella, the most commonly discussed concern with raw diet feeding. We also didn’t pay as much attention to those other bacteria 11 years ago.

I was speaking about antibiotic resistance at the 2019 ACVIM Forum in Phoenix AZ last week, and extended-spectrum beta-lactamase (ESBL)-producing bacteria kept coming up – not just from me, but also in lots of questions from the audience. ESBLs are enzymes that bacteria produce to break down some commonly used (and important) antibiotics, including 3rd generation cephalosporins. These bacteria also tend to acquire various other resistance genes, making some strains highly drug-resistant. ESBLs can be produced by a range of Gram negative bacteria, most notably E. coli, and these bacteria are causing more and more problems. Bacteria can also be resistant to 3rd generation cephalosporins via a different resistance mechanism that’s also of concern. Sometimes, studies focus just on ESBLs while others cover cephalosporin resistance by other mechanisms as well. Resistance by either mechanism is a problem.

One thing that got a lot of people talking at the conference was discussion of things that increase a dog’s risk of shedding ESBLs (or, more broadly, antibiotic-resistant bacteria). One risk factor is previous antibiotic treatment. That’s not surprising. The other big risk factor that’s come up in a few recent studies happens to be feeding raw diets.

  • Our study from 2008 reported dogs that ate raw meat were 15X more likely to shed cephalosporin-resistant E. coli.
  • A UK study reported an 11X higher risk of shedding 3rd generation cephalosporin-resistant E. coli by raw fed dogs. (Schmidt et al. 2015)
  • Another study from the UK reported that dogs that ate raw poultry were 48X as likely to shed ESBL E. coli compared to dogs that didn’t. (They were also 104X (!!) as likely to shed E. coli resistant to fluoroquinolones, another important drug class). (Wedley et al. 2017)
  • In a Dutch study, dogs that were fed raw meat were twice as likely to shed ESBL producing E. coli. (Baede et al. 2015)
  • The same Dutch group also looked at cats, and found that raw feeding was the only factor associated with shedding ESBL-producing bacteria, with a 32X increased risk. (Baede et al. 2017)

These results are actually not surprising.  Resistant bugs can be present in food animals, and those bugs can then contaminate the meat from those animals at slaughter or a subsequent step in the production chain. Measures are taken to reduce the risk, but whether it’s an “ultra-premium” raw diet product or meat from the local grocery store, there’s always some risk of bacterial contamination. That’s why we cook meat, and why we should always use basic hygiene practices to reduce cross-contamination and inadvertent exposure to harmful bacteria in the kitchen and elsewhere.

I won’t get into the whole raw diet discussion here but will hit on some of my highlights:

  • Raw feeding is associated with risk to the pet and owners, and should be avoided whenever possible.
  • In some situations, raw diets should never be fed to pets, including households with young kids, elderly individuals, pregnant women or immunocompromised individuals, or with animals that fit into similar risk groups.
  • High-pressure pasteurization likely reduces contaminant levels but doesn’t sterilize the food. If someone is going to feed a raw diet, they should use one of these diets but still consider the food contaminated.

More information about raw diets and how to reduce the risk when feeding a raw diet is available on the Worms & Germs Resources – Pets page.

CTV has a consumer reports segment and a recent topic involved feeding pets “natural” diets (although no one ever defined what that really means). In the report on the CTV Consumer Alert website (it’s currently about the third story into the video if you just press play, or you can shortcut to it using the link below the main video window), a 26 year old cat is held up as a poster child for the health benefits of raw food. Making it to 26 is a noteworthy accomplishment for a cat, but it’s far from rare, and you can’t know whether the cat survived because of its diet or despite its diet. At the end of the clip, they mention he cat has kidney disease, not an uncommon problem in older cats but one that is often blamed by raw proponents on commercial foods. It’s also not a condition that I’d want to see someone try to manage with a raw diet.

Anyway, the story has the typical statements (including one from a veterinarian) about how raw and “natural” diets produce a healthier animal, stronger immune system and shinier haircoat, but without citing any proof (because there is none) and with no discussion whatsoever about the potential animal and public health impacts of raw meat feeding.

Good investigations are good. Quick reports put together with little thought or consideration of the issues are just time filler. The host, Pat Foran, said in his conclusion that “natural” pet foods have less filler so there’s less to come out the back end of the dog. Well, news reports comprised of filler produce the same kind of by-product.

If you are going to feed raw, at least take the time to research how to do it safely, both for your pet and your household. Raw feeding can be done in a nutritionally sound manner, but it takes time, effort and money. Some people are willing and able to do that, but if you’re not, don’t feed raw. Raw feeding also carries some risk of gastrointestinal disease like salmonellosis in the animal as well as exposure of people in the household to those same bugs. Certain households, particularly those with high risk individuals (e.g. elderly, infants, pregnant women, immunocompromised persons) should avoid raw feeding or only use products that have been high pressure pasteurized. There are a few commercial raw diets that are treated in this manner and these are preferable as the process should kill most relevant bacteria, reducing or eliminating the infectious disease risks to pets and people.

Like many other things in life, the key is being informed so you understand the risks and benefits, and whether recommendations made by people have any substance behind them. Too often, people make a major change like feeding raw based on a comment on a website or from another dog owner, with no clue about the issues and no effort to figure out how to do it right. That’s just asking for problems.

More information about raw diets can be found on the Worms & Germs Resources page.

Delta Society has recently announced a policy prohibiting animals fed raw meat or raw animal products from participating in their Pet Partners program. This policy was established because of research indicating dogs fed raw meat are much more likely to be shedding harmful bacteria like Salmonella and drug resistant E. coli in their feces compared to dogs fed commercial or home cooked diets, and the fact that these dogs come into close and frequent contact with people that are more susceptible to infections and at increased risk having severe infections.

Not surprisingly, internet chat sites are abuzz, and there’s much condemnation and consternation from some. Some of the more vocal minority are stating that they’ll just lie and say that they’re not feeding raw.  I guess such dishonest actions would be based on a combination of ignorance and arrogance – feeding raw is your own decision, but blatantly flouting a policy that was put in place to reduce risks to those most susceptible is stupid and irresponsible.

One of the problems with peoples’ reactions is the fact that they are confusing two separate issues. One debate is whether raw feeding is more healthy or more harmful to the pet. That’s a controversial area, but this policy has nothing to do with that. This policy deals with the increased likelihood that raw-fed pets are shedding harmful bacteria. That’s been very well proven in scientific studies. Do raw-fed pets cause disease in people in hospitals? We don’t know. However, we have enough evidence to indicate there is the potential for increased risk to patients, and that added risk can be eliminated by not feeding raw meat products.

Hopefully, people will realize that this policy has been put in place for a good reason, and that it’s focused on protection of people at high risk of serious illness. It’s not a broad condemnation of raw diets, it’s just a statement that it is not considered appropriate for dogs that will have contact with high risk populations – a recommendation that’s far from new.

Details about this policy can be found here.

Disclosure: I’m a member of Delta Society’s Medical Advisory Board. However, the opinions expressed here are mine and do not necessarily reflect the views of Delta Society.

Meat QuestionFeeding raw meat diets to dogs is a very controversial issue. Some proponents passionately advocate these diets (e.g. the BARF diet) based on vague and unproven recommendations. Opponents cite various studies showing that pets fed raw meat (not surprisingly) have high carriage rates of potentially harmful bacteria such as Salmonella, and reports of diarrhea or nutritional imbalances in these animals. However, there have been only a few good studies looking at the true health benefits and risks of feeding these diets to dogs.

A recent study in the journal Zoonoses and Public Health described the risks of therapy dogs shedding Salmonella and other potentially harmful bacteria. The authors tested 200 dogs over a 1 year period, 20% of which were fed raw meat as part of their normal diet. Dogs fed raw meat were 23 times more likely to shed Salmonella compared to other dogs. They were also 17 times as likely to be shedding extended spectrum beta-lactamase (ESBL) Escherichia coli (a highly drug-resistant form of E. coli).

The study concluded that, because of the risk of Salmonella shedding and the high-risk nature of the patients and other people that therapy dogs interact with, dogs that are involved with hospital/patient visitation programs should not be fed raw meat.

What does this tell us about feeding raw meat to pets?

Although this study doesn’t answer all of the questions about the risks of raw meat diets, it reinforces the fact that pets fed raw meat have significantly higher rates of shedding of potentially harmful bacterial such as Salmonella and antibiotic-resistant E. coli. Eating pig ear treats has also been associated with Salmonella shedding. However, there was no association between a dog being fed raw meat and the animal itself developing diarrhea. In fact, raw-fed dogs had a lower incidence of extra-intestinal infections (combination of eye, ear, skin and urinary tract infections).

In general, raw meat diets should be avoided. While adverse health effects were not reported in this study, disease (including deaths) from Salmonella has been reported in dogs in other studies. While the overall risk may be low, feeding raw meat is an avoidable risk. However, it would be inappropriate to completely ignore the finding that raw-fed dogs had lower rates of certain infections. It is possible that there can be health benefits from feeding raw meat in certain dogs, but the potential benefits must be weighed against the potential risks to the animals and people with which the has contact. Raw meat diets should never be fed to pets that have contact with immunocompromised people (in the household or as part of visitation program), infants or the elderly.

If you are going to feed raw meat to your pet, make sure you take precautions to reduce the risk of infecting yourself or someone else. We’ll post more on that aspect soon.

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.

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.

Raw diets have been in the news a lot lately because of Salmonella contamination. It’s not surprising at all since bacteria like Salmonella, E. coli, Campylobacter and Listeria are expected to be found in raw meat (that’s why we cook it). We know that dogs and cats fed raw meat are at increased risk of shedding bacteria like Salmonella, sometimes with serious consequences to the animals or their owners.

Reducing the risk is a challenge when you know there’s a reasonable chance the food is contaminated, and when the preferred method of control (cooking) isn’t used. Irradiation is an alternative approach, but not something in which a lot of raw feeders are probably interested. High pressure pasteurization (HPP) is therefore increasingly being used to help control bacterial contamination of these products. HPP, as the name suggests, uses high pressure (with minimal increases in temperature) to reduce bacterial loads.

Notice I said reduce, not eliminate.  That’s the problem.

A while ago, I used to go on the assumption that raw food products that underwent HPP were similar in risk to commercial cooked diets, with the disclaimer that we don’t really know for sure. We still don’t know a lot, but what we know now isn’t encouraging, so I’ve had to change that assumption.

I’ve talked to a few people who have done limited investigations of foods treated with HPP, and the results were disappointing. Unfortunately the studies were small and remain unpublished.

A 2016 research abstract gives us a bit more substance (although a proper research paper would be preferred). In that study (Hasty et al. 2016, Reciprocal Meat Conference – Meat and Poultry Safety), raw beef pet food was spiked with E. coli. (A harmless strain of E coli was used in place of a disease-causing strain or other bacteria like Salmonella, presumably because of biosafety concerns.) They used a HPP process that subjected the meat to a standard pressure (600 mpa) for 480 seconds. Then they checked to see if any viable bacteria were left in the meat.

The good news: There was a definite reduction in viable bacteria.

The bad news: It didn’t kill them all.

This doesn’t mean HPP is ineffective. It’s a matter of being aware of what it can do, and what it can’t. It can reduce the number of viable bacteria in the food, and that probably reduces the risk of disease in people and pets. But it does not eliminate all the bacteria, so it can’t eliminate the risk (only proper cooking and handling will do that).

If someone is going to feed a raw diet, I’d still recommend using a HPP-treated diet versus one that has bot been treated. However, people have to realize it’s not a panacea and that they still have to assume the food is contaminated.

Here’s a quick reminder of some basic take-home messages for raw meat feeding:

  • There’s always some risk of bacterial contamination. We can reduce, but not eliminate, that risk.
  • Careful handling is required to prevent cross-contamination of human foods, surfaces and environments. A little common sense when it comes to food handling can go a long way (but it’s amazing how uncommon “common sense” can be… check out Barfblog.com for annals of food safety stupidity).
  • Raw meat diets should not be fed to dogs and cats at increased risk of serious disease (e.g. very young, elderly, pregnant, immunocompromised) or in households where people (or pets) fitting those categories are present.
  • People who feed raw diets should make sure their veterinarian knows this, should their pet get sick. The same applies on the other side of the One Health spectrum – if someone is feeding raw meat to their pet and a person in the household has gastrointestinal disease, exposure to raw meat needs to be mentioned to the physician involved.

More information about raw meat feeding and basic safety practices is available on the Worms & Germs Resources – Pets page.