Advising Clients Who Feed Raw Diets to Pets
Food safety and nutritional integrity of raw meat or eggs are two important health issues that should concern clients who feed these items to the family pet. This article addresses food safety, because it is the more immediate health threat. The nutritional aspects of raw diets are addressed in a separate handout.
Microbial Contamination
Food is contaminated with microbes. Meat from healthy animals becomes conta-minated at slaughter. Meat surfaces become infected with microorganisms asso-ciated with food poisoning during handling, packaging, processing, storage, and transportation. Approximately one third of the poultry sold for human consumption has tested positive for Salmonella. Disinfected grade A eggs that caused salmonellosis were determined to have been contaminated during ovulation; as a result, they were contaminated with the bacteria before formation of the shell. Although many procedures have been incorporated into food processing procedures for both the meat and poultry industries to reduce the level of contamination, bacteria persist: all meat and egg products should be considered contaminated. Raw-meat diets have been used by such industries as zoos, mink farms, and dog racing facilities; the FDA presumes these users are aware of the risks.
Thus, we are most concerned about pet owners who feed raw diets to their pets. Such diets have been documented to contain pathogenic Yersinia enterocolitica 4/0:3, Salmonella species, and Escherichia coli 0157:H7. Commercial raw products, sold frozen or freeze-dried, carry no claim to be pathogen-free; in fact, recent work strongly suggests that they are contaminated. Twenty-one commercially available raw meat diets (beef, lamb, chicken and turkey) cultured over a 4-month period were all positive for E. coli, and 10 were positive for S. enterica. The FDA now has guidelines for companies selling such products to pet owners.
Because most pathogenic organisms are found on the surface of the meat, searing the surface would significantly reduce the potential bacterial load. An option for pet owners who do not want to feed thoroughly cooked meat is to feed whole (not ground) meat, braise the surface, and feed the meat rare instead.
Zoonotic Potential
Pets fed contaminated raw meat shed viable organisms in feces. Evidence validates this public health risk. Salmonella was isolated from 80% of the BARF (i.e., bones and raw food) diets sampled and from 30% of the stools from dogs consuming those diets. Greyhounds and sled dogs fed raw-meat diets have been documented to shed the same subspecies of Salmonella in their feces as that found in their diets. Serovars of Campylobacter species isolated from the diarrhea of dogs was the same as that isolated from the poultry carcasses consumed by the dogs. Only 36% of healthy dogs and 17% of healthy cats harbor low levels of pathogenic salmonellae, which refutes the notion that most household pets are “naturally” infected with these species.
Individuals who clean the cat’s litter box or pick up their dog’s stool should consider the feces contaminated with viable pathogenic microbes. Extra precautions should be taken when persons or pets in the household have immune-suppressive diseases, such as human immunodeficiency virus infection, feline leukemia, or feline immunodeficiency virus infection; are undergoing chemotherapy; or are using anti-inflammatory medications. Extra caution should also be exerted on households with young children to prevent fecal-oral contamination.
Handling Raw Diets
Feeding infected raw diets increases the risk for infection of both human and animal household members. Humans can become infected with food-borne pathogens when handling contaminated meat and egg products. Household transmission of food-borne pathogenic organisms from dogs to humans has been documented.
Veterinarians are trained in zoonotic diseases and thus have a responsibility to inform owners who feed raw meat or eggs of these potential health dangers. Safe practices during handling of the food, feeding dish, and feces should be emphasized, and the need for good personal hygiene must be reinforced. Veterinarians who recommend feeding raw meat or eggs with giving full disclosure of the risks and precautions may face legal ramifications. Salmonella, E. coli, and Campylobacter infection in humans are notifiable diseases, and physicians are required to report cases to local health departments.
Dispelling the Myths
The morphologic and pathophysiologic characteristics of the gastrointestinal systems of dogs, cats, and humans are remarkably similar. Many who advocate feeding raw diets contend that dogs and cats have a more acid stomach and shorter gastrointestinal tracts than do humans, protecting them from pathogenic bacteria. However, there is no difference among these species in regard to gastric pH and no evidence to suggest the difference in length of the gastrointestinal tract is protective to dogs and cats. The stomachs of all mammals secrete acid which keeps the pH of stomach juice low, regardless of what food we are ingesting that day. (That’s why we take antacids for gastritis.) All three species manifest similar clinical signs after ingesting food contaminated with pathogens. The severity of these signs is related to the dose of microbes or toxin ingested as well as the condition of the host.
“Pets need the enzymes present in raw food.” This is a really popular thing right now (propagated by people who sell enzyme supplements) but it’s not proven by any nutritional research, and in fact the need for supplemental enzymes is readily disproven. Digestive enzymes are produced in the salivary glands and the pancreas. Chewing and mixing food with saliva helps to start the digestive process. The stomach grinds food down into a slurry and the acid in stomach juice is mixed with the food to help break it down.
Most of the enzymes that digest food into molecules small enough to pass through the intestinal lining into the bloodstream are produced in the pancreas and secreted into the duodenum – the first portion of the small intestine. These enzymes do not survive the acidic environment of the stomach – and neither do the enzymes present in food that an animal eats. So first, we make our own digestive enzymes, we don’t need to eat them; and second, when we do eat them they are broken down and inactivated prior to making it to the duodenum where they would theoretically become useful.
“Pets cannot digest carbohydrates.” This is sheer nonsense. It’s easy to test digestibility – researchers can easily measure how much of a substance goes into the body and how much comes back out the other end. Carbohydrates are absorbed readily by the digestive systems of cats and dogs. If you give a diabetic cat corn syrup if it has received too much insulin and has a low blood sugar level the blood sugar will go up within minutes – that’s the cat absorbing and utilizing sugar, which is a carbohydrate. We know the calculated digestibility for each kind of carbohydrate commonly used in pet foods – corn, rice, barley, etc. They are all fairly similar, being 80-90% digestible. What isn’t digested is fiber, which is an important ingredient that helps the survival of good bacteria in the intestinal tract and normalizes the stools. In the wild, cats and dogs that eat other animals eat the digestive tract along with the other internal organs – and thus they eat whatever carbs are present in that animal’s digestive tract. If the mouse the cat eats was eating corn the cat will eat corn too.
Wild animals normally eat the internal organs of their prey, they don’t just carve steaks off like humans. Much of their nutrition comes from the organs we commonly refer to as “by-products.” This brings us to “By-products are bad.” Just because humans are squeamish about eating internal organs doesn’t mean they aren’t good sources of nutrition. The liver, spleen, kidneys, heart, lungs and abdominal fat are all extremely good nutritional sources. The by-products that we in America don’t want to eat are all consumed by humans in other cultures, and provide nutrition to people just as they do for animals. Why should we throw millions of pounds of by-products into landfills each year? That’s totally wasteful and environmentally unsound. There is nothing “natural” about a pet eating nothing but human-grade muscle meat.
Food Poisoning Frequency
Frequency of food poisoning in pets is difficult to determine. Veterinarians presented with a family pet for intermittent episode of vomiting or diarrhea would treat the case symptomatically and are unlikely to send samples for bacterial culture and polymerase chain reaction identification. Hence, most if not all cases of food poisoning in the family pet are not reported because of a low level of suspicion and financial constraints.
Raw-meat advocates do not deny but downplay the potential health risks. No scientific evidence exists that a raw diet is superior to any dry or canned pet food. As a result, this practice is associated with health risks to pet and family with no demonstrable benefit.