Dutch scientists are warning pet owners against feeding their cats and dogs raw meat. The meat carries bacteria that can be dangerous to both animals and humans.

Raw meat-based treats for pets is becoming increasingly popular in Europe but scientists in the Netherlands, where 51% of pet owners - an estimated one million people - have adopted the trend, are warning against the diet.

A raw meat-based diet (RMBD), also known as Bones and Raw Food (BARF), contains a number of parasites and bacteria that could be passed on to humans, say researchers from the Institute of Risk Assessment at Utrecht University's Faculty of Veterinary Medicine and the National Institute for Public Health and the Environment.

RMBDs can form all sorts of products crafted for pets: dried treats for cats and dogs, homemade and manufactured meals.

Marketing campaigns assure consumers that they have plenty of positive effects on animals, including facilitating digestion, reducing allergies, improving energy levels or even easing the treatment of diabetes and epilepsy.

But the study, published in Vet Record, exposes these so-called health benefits as "mostly anecdotal" which have not been properly studied. On the other hand, the main health risks present in such a diet have been backed by analysis.

The diets lack several key nutrients and may lead to serious health problems, especially in puppies, the researchers warned. The food also carries a number of bacteria that could infect dogs and spread to their owners.

Listeria, e-coli and toxoplasmosis

The team analysed 35 frozen RMBDs from eight brands bought in ordinary pet stores.

The researchers found that 43% of the products (15 packs from eight brands) contained species of listeria, which causes extremely invasive illnesses.

In 23% of the test packs there were traces of e-coli. Another 20% contained salmonella species. Toxoplasma gondii, the bacteria responsible for toxoplasmosis, was found in 6% of the diets.

Only four packs out of the 35 selected were completely bacteria-free.

Although animals do not always show symptoms of infection, the bacteria can be transmitted to humans and cause different levels of damage.

"Despite the relatively low sample size of frozen products in our study, it is clear that commercial RMBDs may be contaminated with a variety of zoonotic bacterial and parasitic pathogens that may be a possible source of bacterial infections in pet animals and if transmitted pose a risk for human beings," the researchers warned.

"Cats and dogs that eat raw meat diets are also more likely to become infected with antibiotic-resistant bacteria than animals on conventional diets, which could pose a serious risk to both animal health and public health," they add.

The research team urged pet owners to educate themselves before handling RMBDs and feeding them to their pets. They urged manufacturers to print warnings and instructions on raw food product packages.