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 Unfortunately the studies were small and remain unpublished.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.