I’ve had a lot of questions about this week’s somewhat (understandably) vague notice from the Public Health Agency of Canada (PHAC) about an ongoing outbreak investigation of Salmonella infections linked to dog food and treats. The information available is pretty sparse, but there are still some important messages related to what we do know.

From February to August 2025, there have been 27 people infected with Salmonella Oranienburg across Canada, mostly from out west (13 from Alberta, 12 from British Columbia). Six cases were hospitalized, and the outbreak may still be ongoing.

• Reported Salmonella cases are always the distinct minority. For every case that gets reported, someone has to get sick, THEN go to the doctor, who THEN has to order the test, and THEN the person has to actually submit the fecal sample, and the lab THEN has to isolate Salmonella and THEN report it. That’s a lot of steps where things can get derailed for one reason or another. It’s been estimated that there are likely as many as 26 cases Salmonella in people for every case that gets reported to public health.
• Hospitalization are probably less underestimated since testing is more common in sicker people. Regardless, six hospitalization highlights how serious these infections can be.

The link to pet foods is presumably based on interviews of infected people. When a cluster of infections caused by a specific (and uncommon) strain of Salmonella like this occurs, investigators try to find common exposures among the cases to help narrow down potential sources for further investigation. Sometimes finding the source is straightforward, such as when everyone reports eating the same kind of food from the same source around the same time. With outbreaks that are more spread out over months and across the countryidentifying the source is tougher.

“Many” (unclear how many) cases in this outbreak reported handling dog kibble, dehydrated pet diets and freeze-dried treats prior to getting sick, but no common supplier was evident. The fact that not everyone reported that type of contact doesn’t rule out pet food/treats as the source, since no one’s recall is perfect (especially if they were interviewed weeks or months after the were ill). Some people could have had indirect exposure through environmental contamination or from a dog that was infected by eating contaminated food/treats, or through visiting someone with a dog, without realizing they could have been exposed. It’s also possible there’s some other risk factor that just couldn’t be identified, or that the pet food/treats is a proxy for some other exposure (but I don’t have a good idea what that could be).

The fact that kibble, dehydrated pet diets and freeze dried treats are all mentioned shows there’s no clear direction towards what might be the source. If I had to rank the probable risk from these products, I’d put dehydrated diets first, treats next and kibble last.

• Dehydrated diets are raw diets. Raw animal-based products are high risk for Salmonella and other pathogens. Dehydration is not a pathogen elimination tool. It will have an effect on some bacteria, but not all.
• Freeze-dried treats are also primarily raw animal-based products, and are therefore also high risk for Salmonella and other pathogens. Freeze drying is likewise not a pathogen control tool, in fact it’s a pathogen storage tool – if we want to preserve a bacterium for a long time in the lab, we can freeze dry it so it’s shelf-stable. Myriad raw animal based treats are available too. Go into any pet store and you’ll likely find bins and bags of dried animal bits of various sources (e.g. liver, pig ears, rawhides, bully sticks and much, much, more). Bulk bins of these pose even greater risk because one contaminated item can cross-contaminate the whole bin.
• Kibble is initially cooked and extruded, which should kill any pathogenic bacteria in the raw ingredients. However, it’s still a plausible source of Salmonella as there have been infections linked to kibble. This may occur from post-extrusion contamination (e.g. contaminated flavour enhancers that are sprayed on the kibble after), or through contaminated machinery. The risk is really low, particularly compared to raw diets, but it’s not zero. Kibble is also probably a less likely source in this outbreak because a specific product would likely be more easily identified during the interviews. However, if contamination occurred because of an ingredient that was sourced by different companies, or if different companies’ food was produced in the same plant (which does happen), then the link would be harder to identify.

Hopefully we’ll get more details as the investigation continues. If the outbreak is ongoing, there will be more data that could help identify the source, and now that public health personnel are aware of the potential dog food/treat link, there might be more detailed questions and quicker testing of products.

• Testing of dog food and treats to confirm the source requires rapid identification of the issue so that the source food/treat is still possibly available to test. The longer it takes, the less likely that is.
• It’s unclear if any testing of products has been done so far in this outbreak. At this point, with no clear source, testing of food and treats in affected peoples’ houses would be a fairly low yield fishing expedition, especially given time delays. It would be easier to pick up in kibble, since there could be more bags of the lot around to test, if an entire lot was implicated. Dehydrated diets and treats are usually made in smaller batches, so by the time an issue is identified, there may be none left to test.

It’s hard to say if we will get a final answer as to what caused this outbreak, but in the meantime, it’s a good reminder of some basic infection control practices. PHAC’s advice is pretty basic but like a lot of things in infection control, basic practices are the core prevention methods:

• “To prevent illness, individuals are advised to practice good hand hygiene and frequent handwashing after contact with dogs, their food and treats.”

Good basic hand hygiene, preventing cross contamination of pet food and human food, keeping higher risk people (especially young children) away from pet food and food bowls, avoiding raw diets and raw animal-based treats (which are abundant, and people don’t often realize are raw) and good hygiene when handling pet feces are all easy, reasonable and critical core prevention practices, especially until (and even if) the true source of this outbreak is identified.