Research Update: Raw Diet Risks
Summary
There have been a number of recent high profile cases of pets or even people becoming severely ill or even dying from bacteria or viruses that they caught from raw pet foods. A number of scientific studies have also been published in the last few years, all of which further elaborate the health risks that raw pet foods can pose due to contamination with bacteria, viruses, or parasites. In this post, we summarize a new study from Cornell that tested commercial raw cat foods and traditional canned or dry cat foods for bacteria and parasites and also quantified bacterial genes associated with antibiotic resistance. The study found that bacteria could be grown from only raw foods, including frozen and freeze-dried products and found many bacterial genes associated with antibiotic resistance in the raw foods, which means that using these diets not only comes with the risk of bacterial infections, but also the risk of infections that are resistant to typically used antibiotics.
We’ve posted about potential risks from raw meat diets previously, but there have been a lot of new developments in the last few years that are worthy of a follow-up post. Probably the most news-worthy relates to a number of cats, both exotic and domestic, that have died in the last year due to H5N1 influenza (aka “bird flu”) obtained from raw poultry and/or raw milk in their diets, including several commercial raw cat foods . Cats who eat contaminated food have had an extremely high fatality rate – > 50%. You can read more about this issue here: https://www.avma.org/news/feline-avian-influenza-cases-spark-concerns
Another rather chilling story involved a child who got infected with E. coli O157:H7, a very serious form of the bacteria that can cause kidney failure. Her infection was traced back to samples of a commercial raw frozen diet fed to the family dog. Of particular concern is that the manufacturer refused to recall the diet after it was linked to her illness and in late September, the FDA issued another advisory, this time for Listeria and Salmonella in products from the same manufacturer. Here are the FDA notices: https://www.fda.gov/animal-veterinary/outbreaks-and-advisories/fda-advisory-do-not-feed-certain-lots-darwins-natural-pet-products-pet-food-due-e-coli-o157h7-and and https://www.fda.gov/animal-veterinary/outbreaks-and-advisories/fda-advisory-do-not-feed-two-lots-darwins-natural-pet-products-biologics-dog-food-due-salmonella-and
These and many other incidents and recent studies highlight the persistent risk of bacterial, viral, and parasitic infections that raw pet foods can pose to both pets and people. The FDA last investigated in 2011 ( https://www.fda.gov/animal-veterinary/animal-health-literacy/get-facts-raw-pet-food-diets-can-be-dangerous-you-and-your-pet ) but there have multiple university studies since then assessing risk for contamination and antibiotic resistance from commercial raw pet foods. One of the most recent studies is a publication by a team from Cornell University in a journal called Communications Biology, which is part of the prestigious Nature journal family: https://www.nature.com/articles/s42003-025-08756-8
In the study, the researchers purchased 85 samples of commercial raw cat foods (28 refrigerated or frozen, 49 freeze-dried, and 8 in kibble form) along with 27 cooked pet foods (22 canned and 5 kibble). They then tested the foods for DNA from pathogenic bacteria and parasites, cultured the foods in petri dishes to see what grew, assessed for the presence of bacterial genes that could lead to antibiotic resistance, and also tested them for common pet food proteins to see if they matched their ingredient lists.
Here were their main findings:
- Almost 18% (15/85) of samples contained animal proteins that were not present on the label, with chicken and turkey being the most common unreported components. Slightly more cooked diets had this issue than raw (9 vs 6) but that could have just been the luck of the sampling. This issue has been reported before in many studies and could be due to contamination with other proteins present in the facility or manufacturers intentionally (and illegally) swapping proteins. Either way, it can be an important issue for pets (or people) with food allergies.
- The raw cat foods were more likely to contain DNA from pathogenic bacteria than cooked foods (the presence of DNA doesn’t mean that the bacteria are still alive or infectious, just that they were or are present).
- Potentially dangerous bacteria could be grown from 42% of the raw cat foods but from none of the cooked cat foods. These bacteria included Salmonella enterica, E.coli, and Klebsiella. Viable bacteria were cultured from all forms of raw foods but were most common in frozen raw pet foods. Some of these bacterial strains were very genetically close to strains associated with human infections, including one Salmonella enterica strain that was identical to a reported human infection strain.
- Raw cat foods contained more bacterial genes associated with antibiotic resistance.
- Parasite genes (but not necessarily live parasites) were found only in raw cat foods.
It’s not at all surprising that foods containing uncooked meat would have higher concentrations of bacteria and parasites, but one thing that wasn’t addressed in this paper is that some commercial raw pet food companies are using technology such as high-pressure pasteurization or processing (also called ‘HPP’) to reduce bacterial and viral concentrations in raw foods to improve safety. The authors of this study did not specify if any of the raw cat foods selected for this study utilized that technology. If they did, one would hope that those diets would be among those where live bacteria could not be grown!
While not a major finding of the study, another interesting thing was that all of the freeze-dried cat foods were confirmed to be raw when the manufacturers were contacted, yet only a “small minority” of the 49 freeze-dried products clearly stated on the label that they were raw. Many pet owners are unaware that most freeze-dried pet foods and treats are freeze-dried raw instead of freeze-dried after cooking and thus underestimate potential pet and human health risks from feeding these products. The lack of clear labeling makes it nearly impossible for pet owners to assess risk without contacting the manufacturers for each individual product. Until more accurate labeling is required or commonplace, it seems prudent to assume that all freeze-dried met pet food or treats are raw until proven otherwise.
The take-home message from this study and many others is that all forms of raw pet food and treats carry the risk of bacterial, viral, or parasitic contamination and that these infections can make dogs, cats, and even people very sick! Even worse, many of the bacterial strains found carry genes for antibiotic resistance. These genes not only cause problems for the animal eating the food and the people living with the animal but can also be transferred to other bacteria, thus increasing the likelihood of antibiotic resistance, which is already a serious concern in both human and veterinary medicine.
The good news is that you can easily reduce the risk for your pet and family! Feeding cooked pet foods will reduce infection risk and reduce the risk of spreading antibiotic resistance genes in both pets and people.