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, can get sick from it and owners can be infected (from the pet or cross-contamination from the food…always hard to sort that out).
More recently, I’ve been concerned about multidrug resistant E. coli and related bacteria. I think this may 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, particularly extended spectrum beta-lactamase (ESBL) producing bugs.
Yet, there are various other issues. A recent paper in the journal Epidemiology and Infection (Kaindama et al) describes a cluster of human E. coli O157 infections in the UK that was 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 gut of food animals (mainly cattle) and can therefore sometimes contaminate meat.
In this cluster, 4 people infected by a similar strain of E. coli O157 were identified.
- They got sick within a one-month period in 2017.
- I’m guessing three were 6 year old kids, based on the median and age range provided in the paper. The burden of zoonotic diseases often falls disproportionately on kids.
- Three of them were hospitalized, and one died.
During the investigation, no typical sources of E. coli O157 exposure were identified. The only commonality between cases was all had contact with dogs and a history of consuming raw carrots. Three of affected people 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. However, different strains were found. That’s not too surprising since contamination will 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 strain from a different origin. Finding different strains doesn’t round out the story as nicely but it maybe highlights more concern. This wasn’t a one-time point exposure because of some strange event. Contamination of raw pet food with this concerning bacterium might be more common than has been recognized.
Whether these are rare cases or the small subset of diagnosed cases is unclear. This was identified because:
- It was a cluster of infections
- 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 and batch-to-batch variation. 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 people from raw diets. I don’t like to see them fed. That’s particularly true in households with people or animals that are at higher risk of severe disease (young, old, pregnant, immunocompromised). There are ways to reduce the risk, both in terms of products that are purchased (e.g. high pressure pasteurization likely reduces the risk a lot but doesn’t eliminate it) and how raw diets are handled. More information about feeding raw diets and reducing the risk is available in our Resources section.