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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.

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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.

I got a question about an old post on this topic, so I decided to add a bit of information and re-post it. Not much has changed since it was written in 2018, apart from more reports of people and pets getting sick from raw pet food and raw treats.

“Is freeze-dried raw pet food any different than fresh or frozen raw diets, from a microbiological standpoint?”

We don’t have much pet food-specific research, but there’s little reason to believe there would be much difference between these types of diets when it comes to the microbes we’re concerned about. When I want to preserve bacteria, I freeze them or freeze-dry them – those are actually the preferred methods for long-term storage of bacteria. Freezing or freeze-drying is a pretty hospitable process and state for most bacteria. Some, such as Campylobacter, don’t tolerate freezing (or especially fresh-thaw cycles) as well as others, so freezing or freeze-drying might have some impact on those specific bugs. For the higher profile pathogens like Salmonella, E. coli and Listeria, it probably doesn’t have much of an effect. I can see there being some reduction in bacterial numbers but probably nothing substantial, and certainly not enough that I’d consider it when deciding whether it’s an appropriate diet for a particular pet and household.

The story is quite different for some parasites. Many parasites and parasite eggs don’t tolerate freezing – that’s why fish for sushi is typically frozen at some point before it is served. Some are hardier than others, though. Toxoplasma, a potentially important foodborne parasite, is susceptible to freezing, but only if the temperature is low enough and the time is long enough (e.g. -12C for 3 days will kill most Toxoplasma cysts.  To put that into context, typical household freezers run around -20C).

So, the take home message is that for of the microbes that we’re worried about with raw meat,  freezing or freeze-drying is NOT a food safety practice. It’s food preservation, not bacterial control.

Another point to add… advertizing around pet diets is variable and sometimes quite dodgy. I just checked two websites selling freeze-dried raw diet. One had good info. The other… well… not so much.  Don’t let company advertizing be your infection control guidance.

More information on raw diets and toxoplamsosis are available on the Worms & Germs Resources – Pets page.

The Public Health Agency of Canada (PHAC) has announced an outbreak of E. coli O157 infections in people linked to Carnivora brand raw pet food, and Health Canada has issued a recall of a number of Carnivora products due to potential contamination with E. coli O157. Illnesses have been reported in four individuals in total, from British Columbia, Alberta and Manitoba.  All affected individuals had exposure to Carnivora brand pet foods, and two were hospitalized due to their illness.  The concern is that the majority of infections might be overlooked, as commonly occurs in such outbreak. The outbreak once again highlights the importance of querying animal contact and contact with high risk (raw) pet foods when foodborne diseases are investigated. While people were presumably not eating the pet food, there is the potential for cross-contamination of human food when handling raw pet food, as well as potential for exposure to pathogens through things like contact with pet food bowls and pet feces.

The main concern with raw pet food tends to be Salmonella; however, E. coli O157 is another significant concern because of the  potential severity of disease. A death was reported in a UK a couple years ago from exposure to E. coli O157 from contaminated pet food.

People who have had contact with the recalled food should be aware of the risk. The odds of a problem are low in most cases and there’s nothing to do if everyone’s healthy. However, it’s critical that healthcare providers be informed of potential exposure to E. coli O157 if someone gets sick (e.g. diarrhea). That’s particularly important for this bug because use of antibiotics (not usually needed for people with diarrhea, though they’re over-prescribed anyway) is a major risk factor for inducing hemolytic-uremic syndrome (HUS), a potentially fatal complication of infection with E. coli O157.

While most dogs and cats that eat raw diets are fine, and most owners don’t get sick, it’s clear that feeding raw diet or raw animal-based treats (e.g. pig ears) is associated with risks to the pet and any human contacts. I’d rather people not feed raw diets to their pets, particularly when the pet or household members are very young, elderly, pregnant or have compromised immune systems. If none of those risk factors are present and someone wants to feed a raw diet, I’d still rather they didn’t, but there are some things that can reduce the risks, as outlined on the Worms & Germs infosheet on raw diets available on our Resources – Pets page.

Oh, and don’t go to the company’s website for accurate information about risk and risk mitigation. They bury some good prevention recommendations in a pile of often out-of-context dialogue to try to deflect any concerns and the typical raw diet misinformation. Some other raw pet food companies are up front about the risks and prevention measures – I have a lot more confidence in companies like that.

A recent study looked at human illness associated with raw pet food and has led to headlines such as “It is safe to feed raw pet foods.”

Did the study say that?  No, it did not.

If you asked 100 people if they had a foodborne disease in the past year, I assume few would say “yes,” despite the widespread estimate that about 30% of people get a foodborne illness every year. If you ask people if they got a foodborne disease from a specific food, the numbers would be even weaker / lower. People generally don’t have good recall for things like that, since we don’t usually recognize a cause when we get intestinal disease. The odds of someone linking their vomiting or diarrhea to their pet’s food are low, especially if they have no awareness that their pet’s food is a risk. Even if someone thinks about the source of their disease (which probably isn’t overly common), would they think about their pet’s food as the source, versus other foods in the house, versus a restaurant, versus anywhere else they ate? I suspect the average pet owner would not.

The problem isn’t the study, it’s how the study has been interpreted. It didn’t (and couldn’t) get a good estimate of the burden of disease associated with raw pet diets. The title of the study is Owners’ perception of acquiring infections through raw pet food: a comprehensive internet-based survey (Anturaniemi et al, Vet Rec, 2019). It looked at perceptions, which is useful, but has a lot of limitations.

The study was an internet survey of pet owners who fed raw diets. Internet surveys are easy to do, but are problematic for a few reasons. When you ask 1000 people to complete a survey and 990 respond, you know you captured your population well. If 10 respond, you know you haven’t and maybe you have a biased group of respondents (e.g. people that were more motivated / biased one way or another might be more likely to respond). With an internet survey, you generally have no idea how many people got the survey, and therefore no idea what percentage of people responded. The survey was disseminated through the research group’s Facebook page and through the researchers’ own academic, private and industrial contacts, so the people invited may not reflect the typical pet owning population. That doesn’t mean the results are useless (I’ve done internet surveys myself), it just means we need to be careful interpreting results. I tend to approach surveys as tools to get some basic information to figure out what questions to address more thoroughly, rather than tools to  answer specific questions.

The main question that was asked in this study was “Are there/have there been people in your household that have become sick from handling raw pet food or that have become sick from contact with a raw pet food eating pet?”

That’s a question we want to answer. However, it’s not a question the general public is well equipped to answer themselves.

  • The sample size was large (16,475 households), which is good, but there’s not much information about the households to determine how reflective they are of the broader population.
  • Most had been feeding raw diets for years, but some were pretty recent (e.g. 0.1 years, which is not much time for someone to get sick as a result).
  • Overall, 0.2% of households reported a “confirmed” transmission from the pet or food. That’s a relatively small number, but 0.2% per year means a lot of sick people. I’m actually surprised that people reported getting sick from their pet’s food at all. I’d expect massive under-recognition and under-reporting, so seeing any reports is interesting. If you consider that in most foodborne disease, reported cases usually account for less than 10% of the real number (and probably less than that here), the true burden of disease based on these numbers is quite a bit higher, to a level I’d certainly be concerned about.
  • Salmonella and Campylobacter were most the commonly reported infections. However, most of the time, there was no effort to confirm the pet food as the source, so it’s hard to say what the numbers really mean.
  • In situations where there was “confirmed” transmission, 31% of the time the pet was sick at the same time. That maybe strengthens the association between human and animal disease, but also maybe shows potential bias. Are people more likely to blame the pet/food if both they and their pet are sick at the same time, and blame human food or not consider pet food if the pet isn’t sick? I have no idea, but that could greatly influence self-reported data.
  • Interestingly, raw foods were handled in the same place as human food and with human food utensils significantly more often in the negative households. That’s the opposite of what I’d expect. The counter argument might be that people who handle raw pet food poorly are not tuned into the risks and are therefore less likely to identify or blame the pet food if they get sick.

The authors sum things up in a more balanced manner than internet headline writers:

“As a conclusion, this large study population from all over the world shows that the transmission of zoonotic pathogens might happen, but it seems to be sporadic. It is clear that the precise source of the pathogen is often challenging to find, which makes the interpretation of the result difficult. However, studies using different kind of approaches should be conducted in the future to be able to get a better understanding of the true risks or possible health benefits of feeding raw food diets to pets. This way the true pros and cons can be accurately analysed, before asking pet owners not to feed their pets with a nutritionally balanced raw diet.”

That’s a good conclusion. This study provides some baseline information and can help tailor future studies. It helps us figure out how to get a good answer rather than giving us a good answer now.

More information about ways to reduce the risk from feeding raw diets is available on the Worms & Germs Resources – Pets page.

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.