The biggest threat to global health could potentially come in the form of man’s best friend. This is what new research suggests after multidrug-resistant bacteria were found in dog food – which triggered fears of a possible international health crisis.
A new paper, presented at the European Congress of Clinical Microbiology and Infectious Diseases (ECCMID), warns that “the tendency for dogs to be fed raw foods may be to nourish the spread of antibiotic-resistant bacteria.”
Researchers from UCIBIO, the Faculty of Pharmacy at the University of Porto in Portugal, examined various dog food samples from supermarkets and pet stores.
The study revealed that Enterococci, a bacterial genus commonly found in the intestines of humans, were present in more than half of the samples analyzed.
The concern comes from the fact that this type of bacteria is often inherently resistant to antibiotics, which means that some species of enterococci can lead to dangerous outbreaks. For example, in the last two decades in the United States there have been clusters of infections related to VRE (Vancomycin-resistant enterococci) – often originally contracted from a hospital.
An estimated 700,000 people worldwide die each year from drug-resistant infections. The UN says this figure could rise to 10 million by 2050 without sufficient action. Antibiotic resistance is classified by World Health Organization (WHO) as one of the biggest threats to global public health.
“This study shows that dog food from international brands is a means of clinically relevant enterococci that carry resistance to last resort antibiotics and relevant virulence genes, thus placing pet food as an important source of the spread of antibiotic resistance,” says the paper’s author. dr. Ana Freitas, dr. Carla Novais, dr. Luísa Peixe and colleagues from UCIBIO.
Dr Freitas and her team looked at 55 samples of dog food (22 wet, 14 raw frozen, 8 dry, 7 treats and 4 semi-wet) from 25 brands available in Portugal and the rest of Europe. The raw frozen foods included beef, goose, duck, salmon, turkey, chicken, lamb and vegetables.
More than half (54 percent) tested positive for Enterococci, with 40 percent of this type of bacteria found to be resistant to several types of antibiotics. Nearly a quarter were found to be resistant to linezolid, a drug considered a ‘last resort antibiotic’ – used only where other drugs have not treated an infection. Resistance to this specific antibiotic is particularly alarming.
The rise of raw dog food
Raw dog food, often sold in frozen chunks, has grown rapidly in popularity over the past five years. Data from Google shows a sharp increase in public searches for the product in 2020, especially in the UK.
Owners believe that feeding dogs raw meat is healthier for their pets, claiming to see improved dental hygiene, increases in energy levels as well as healthier coats and skin. However, some veterinarians warn that there are health risks for the wider household and dogs with compromised immune systems.
The UCIBIO study showed that multidrug-resistant Enterococci were present in all analyzed raw-frozen samples – including bacteria-resistant to linezolid. Only three of the non-crude samples contained multidrug-resistant species of Enterococci.
The authors of the paper warn it with an estimated 90 million dogs in Europeand nearly 500 million worldwide, dog food can be a dangerously overlooked source of antibiotic resistance globally.
“The close contact between humans and dogs and the commercialization of the brands studied in different countries pose an international public health risk,” adds Dr. Freitas.
“European authorities need to raise awareness of the potential health risks when reviewing the feeding of raw pet foods and the preparation of dog food, including the choice of ingredients and hygiene practices.
“Dog owners should always wash their hands with soap and water immediately after handling pet food and after defecating.”
Antibiotic resistance in the broader meat industry
While the recent UCIBIO study focuses on mass-produced dog food, drug-resistant bacteria are also a growing problem in meat for human consumption.
For decades, antibiotics were used for non-therapeutic purposes in livestock production. To meet consumer demands, antimicrobials were used to promote the growth of some animals – as well as to increase milk production in cows. In 2001, it was estimated that about 90 percent of antimicrobial use in the United States was for non-medicinal reasons in animal husbandry.
This has long been a problem around the world, not just in the United States. However, Sweden, Denmark and a handful of other countries began to address that practice in animal husbandry 40 years ago. The EU banned the use of antibiotics for growth purposes in 2006, and the US did the same in 2017.
However, research suggests that two-thirds of antibiotic consumption worldwide is in livestock. Although regulation has helped reduce practice (antibiotic use in livestock has fallen by 50 per cent in the last five years in the UK) – it is still far from fully addressed.
In Oceania and Asia, the rate of sale of farm antibiotics per. unit pets is four times higher than in Europe.
Basic Antibiotic-resistant bacteria are a concern in all meat production – whether it ends up being food for humans or pets.