After starting off like a simple recall of potentially Salmonella-contaminated dry pet food, the Diamond Pet Food problem has now expanded into a multistate outbreak of salmonellosis in humans linked to exposure to the contaminated pet food. At last count, there were 14 affected people from 9 US states, including 5 who required hospitalization. These numbers could increase since so far they only include people who got sick up to April 1 (because it takes time for Salmonella to be grown in the lab, sent to CDC for testing and the result investigated, later cases may not have been reported yet).
This outbreak involves Salmonella Infantis, a strain that is uncommonly identified in people. Finding an increased number of infections caused by an unusual strain makes it easier to identify an outbreak, as was presumably the case here. This strain has also been isolated from various types of pet food that were produced at the Diamond Pet Foods’ South Carolina plant. Despite the name, this strain of Salmonella is not more likely to infect infants, and people ranging from less than 1 year to 82 years of age have been infected.
Details about the types of contact people had with the pet food are limited. 70% of infected people reported having contact with a dog the week before getting sick. How the other 30% could have been exposed is unclear. Sometimes peoples’ recall is poor, especially if they had transient contact with a pet. Individuals could have been exposed from environmental contamination when visiting a household where contaminated pet food was fed, without having direct contact with a pet. It’s also possible some cases are not directly related to the outbreak and co-incidentally were exposed to the same strain from some other source.
Since we see periodic outbreaks associated with dry pet food, does that mean that other types of pet food are safer? Not really. Canned food is ultimately the safest because of the heat processing, but it’s not practical for all animals.
Typically, after a report like this, I get a barrage of emails from people saying "See… we don’t have large outbreaks from raw food diets so they are safer." Unfortunately, that’s not the case. High pressure pasteurization (HPP) of raw food, a process that uses pressure with minimal heat to kill bacteria, is an effective method for reducing contamination of such products with harmful pathogens like Salmonella, and HPP is now being used by a couple of companies. These raw diets should be quite safe from a Salmonella standpoint. Otherwise, the risk of Salmonella contamination of raw pet foods is still very high, and if anything, the dry food outbreaks show how people can be infected from contaminated pet food.
Why don’t we see large outbreaks associated with raw food? Outbreaks get detected because certain patterns or unusual findings are identified. Raw pet food associated outbreaks probably occur but are not as readily identifiable since raw meat contamination is common but involves variable Salmonella types that regularly change. In a situation like that, you can potentially have lots of people getting Salmonella from raw food, but if there is limited commonality in strains and products, it doesn’t get picked up as an outbreak. That’s particularly true when the strains that are involved are the common ones found in food, since they would often be dismissed on the premise that the person likely got it from some unknown food source. Without large numbers of cases in an area or a cluster of unusual strains, the investigation wouldn’t likely get very far and nothing would be reported.
How do reduce the risk of getting Salmonella from pet food (or your pet)?
More information about both Salmonella and issues pertaining to raw diets (including how to reduce the risk) can be found on the Worms & Germs Resources – Pets page.