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Raw Dog Food Might Be Driving the Spread of Dangerous Superbugs

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Image: John Minchillo (AP)

Raw dog food contains alarming amounts of antibiotic-resistant bacteria, making it an under-appreciated “international public health risk,” according to new research.

Scientists, including those with the Centers for Disease Control and Prevention, have advised against the burgeoning trend of feeding raw food to pets, citing the risk of spreading germs like E.coli, Salmonella, and Listeria. New research presented at the European Congress of Clinical Microbiology & Infectious Diseases (ECCMID) highlights another danger posed by raw pet food: exposure to multidrug-resistant bacteria.

The team found upsetting levels of antibiotic-resistant bacteria in dozens of dog food products sourced from grocery stores and pet shops in Portugal. Some of these superbugs were found to be the same as those documented in European hospital patients, potentially exposing dog food as an “international public health risk,” as Ana Freitas, a co-author of the study and a researcher at the University of Porto in Portugal, said in a press release.

Drug-resistant bacteria are a significant health risk because they make minor scrapes and infections far more dangerous and sometimes even life threatening. Figures provided by the World Health Organization show that, globally, around 700,000 people die each year from these superbugs, and it’s a problem that’s only going to get worse. The WHO estimates that, by 2050, 10 million people will die each year from multidrug-resistant germs. Hence the importance of identifying the source of these pathogens and finding ways to prevent their ongoing spread.

“Raw meat-based diets are increasingly popular for feeding dogs, but the extent of antimicrobial-resistant bacteria in raw dog food is rarely addressed globally,” wrote the scientists in a research letter published by the CDC.

To address this gap in knowledge, the team analyzed 55 samples of dog food sourced from shops in Portugal. These samples included 25 international and national brands and were categorized as wet, dry, semi-wet, treats, and raw-frozen, the latter of which included foods like duck, salmon, poultry, lamb, goose, beef, and veggies.

Of these samples, 54% contained traces of Enterococci. This bacterium is present in human intestines and vaginal tract, and also in soil and water, but it can “spread from one person to another through contact with contaminated surfaces or equipment or through person to person spread, often via contaminated hands,” according to the CDC.

Enterococci is becoming increasingly tolerant to antibiotics, including vancomycin, teicoplanin, and linezolid. In 2017, vancomycin-resistant Enterococci was responsible for about 54,500 infections and 5,400 deaths in U.S. healthcare settings.

All raw dog food sampled in the study contained multidrug-resistant Enterococci, whereas only three non-raw samples contained the bacterium. Over 40% of the Enterococci were found to be resistant to common antibiotics, such as erythromycin and tetracycline, as well as last-resort antibiotics such as vancomycin, teicoplanin, and linezolid.

The “diversity and rate” of Enterococci was “unexpectedly high,” the scientists wrote in the research letter. Genetic sequencing confirmed some of the germs as being of the same kind found in hospital patients in Germany, the UK, and the Netherlands, and also in livestock and wastewater in the UK. A related study from the same team, the details of which were also presented at the online meeting, suggests genes associated with multidrug-resistant bacteria are being passed to humans through dog food.

Another team from Portugal presented evidence at the same meeting showing that the mcr-1 gene—which helps bacteria resist antibiotics—is being passed between humans and their pets. This research paper, which still needs to be submitted to a science journal, presents a “nightmare scenario” in which mcr-1 is “combining with already drug-resistant bacteria to create a truly untreatable infection,” according to a press release.

Freitas and her colleagues warn that raw dog food could be an emerging vehicle of transmission of antibiotic resistance, and that’s because this type of food consists of many raw ingredients taken from different sources, including livestock animals involved in intensive farming, they write. “European authorities must raise awareness about the potential health risks when feeding raw diets to pets and the manufacture of dog food, including ingredient selection and hygiene practices, must be reviewed,” said Freitas in the release.

As for dog owners, they should wash their hands with soap and water immediately after handling pet food and after picking up dog poop, she added.

Good advice. And better still, stop feeding your pets raw meat.