Four products (11%) contained the parasite Sarcocystis cruzi and another four contained Sarcocystis tenella.
"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.
"It has been claimed that feeding pets raw meat results in a better overall condition of the animals and could have a supportive role in controlling and preventing certain medical conditions in both dogs and cats such as allergies, skin and gastrointestinal tract problems", said lead researcher Paul Overgaauw, from Utrecht University. Humans may also be exposed to harmful pathogens when cleaning up an infected animal's waste or when an infected animal licks its owner's face or hands.
Raw meat diets for pets have become increasingly popular, but there is no evidence that they are healthier than typical pet foods, the researchers said. "But I can imagine that cross-contamination in the kitchen during preparation of the food, and cleaning of the food bowls-as well as direct contact with infected animals-are the highest risks", he says. In an email, the study authors said that raw-meat pet foods for sale in the United States are "without a doubt similar" to those tested in the study.
RMBDs can form all sorts of products crafted for pets: dried treats for cats and dogs, homemade and manufactured meals. Conventional pet food is also heated during processing, which kills all germs.
"Feeding of freshly prepared, non-frozen raw meat based-diets to companion animals cannot only result in infection and disease in the animals, but also poses a risk to public health and livestock farming through shedding of pathogens into the environment", the researchers conclude.
Commercial raw-meat pet foods sold in the United States and Europe contain "all kinds of meat, organs, and bones, sometimes with vegetables or fruits added", says Overgaauw.
Others argue that it's more natural for a carnivorous species to eat raw meat products.
"It is important to encourage awareness of the possible risks associated with feeding RMBDs to companion animals, and pet owners should be educated about personal hygiene and proper handling of RMBDs", the study said. "They think they are feeding dogs how they would eat in nature, like a wolf".
Past year a charitable scheme which sends dogs into schools to help children read, Burns By Your Side, announced it had banned the use of animals fed on raw meats because of the health risk to children.