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Both raw-feeding and processed diets come with a risk of spreading food-borne illness, such as Salmonella and Campylobacter. It is commonly thought amongst veterinarians that raw-feeding poses a significantly greater risk, and on the basis of this, they warn against raw-feeding. The AVMA has drawn erroneous and premature conclusions from the scientific literature that they have examined (as explained below, and here). There is currently insufficient evidence to elucidate which is the greater risk - raw, or processed. This evidence can not become available until there is a widely accepted definition of raw diets - allowing for standardised comparisons. While we wait for the evidence, there are two things to consider:
In the absence of a strong body of scientific evidence, you - the consumer - will need to decide for yourself what course of action makes sense for you and your pets.
Earlier this year the American Veterinary Medical Association (AVMA) released a statement regarding raw-feeding1. They referenced several studies which suggested that raw protein sources may be contaminated with pathogenic organisms, and that pets may develop clinical illness from these organisms.
They also stated that cats and dogs with either clinical illness, or subclinical infection are a health risk to other animals and humans. They concluded with a recommendation to (in the interests of public health) avoid feeding raw food (inadequately treated animal-source protein) to cats and dogs.
In the first study referenced by the AVMA2, ten dogs in a non-randomised, non-blinded study were fed a processed, dry, commercial diet; and ten were fed a Bones and Raw Food (BARF) diet. The commercial diet was not named. There was no information regarding the source, and storage conditions of the chicken used for the BARF diet. This information would be of value when interpreting the results.
Food samples and stools were cultured for Salmonella serovars. None of the commercial diet group tested positive for Salmonella in either their food samples or their stools. Eight of the ten BARF food samples, and three of the ten stool samples tested positive for Salmonella. Only one of the stool samples tested positive for the same serovar of Salmonella as was detected in the food sample. One dog that tested positive in its stool had no Salmonella found in its diet. Therefore, only one of the ten dogs was shown to be shedding the pathogen that was detected in its diet. None of the dogs in either group displayed clinical signs.
The study was, in the words of the authors, “limited”. They point out that, due to a small sample size, the results were not statistically significant. In order for this study to support the AVMA’s stance, they must also provide evidence that there is a causal relationship between the shedding of pathogens in stool, and ill-health in humans. Due to the regularity with which commercial pet foods are recalled due to pathogenic contamination, they must also show that this causal relationship is smaller, or non-existent, in commercial pet foods.
The second referenced paper3 examined the human health implications of Salmonella contamination, and discussed the theoretical risk of disease.
The authors of the paper stated that, despite the increasing popularity of raw diets, and despite the presence of Salmonella on some raw diets (particularly those of chicken-origin) “no confirmed cases of human salmonellosis have been associated with these diets.”3 The AVMA report did not mention this.
Although there have been reports of raw-fed dogs developing clinical Salmonellosis, there have been none associated with commercial raw diets.
The authors highlighted the fact that there is no common agreement about what constitutes a raw diet. This makes the interpretation of controlled studies, where ‘raw diets’ are compared with commercial diets, very difficult. The authors incorrectly stated that “raw food diets are made from animal by-products, they are not considered to be fit for human consumption, and, as such, they are not subject to the same regulations as is food intended for humans.”3 This further highlights the confusion surrounding a definition of a raw food diet. An appropriate raw food diet makes use of the whole carcass, not just the parts that humans do not use, and is routinely sourced from the human food chain.
The paper references a “limited number of reports”3 of human infection associated with ill, or carrier animals.
As stated in the paper, processed pet treats of animal origin are commonly found to be contaminated with Salmonella, and have been associated with numerous outbreaks.
The authors suggested that pet owners be educated about the potential health risks that may be associated with raw feeding, and animal-origin pet treats. It would seem prudent, then, to also educate the public about the established and widespread contamination issues surrounding commercial pet foods. They also suggested that animals used within retirement homes and hospitals should not be raw-fed because of the possibility that the diet was contaminated. Again, the contamination of commercial diets should be considered too.
The third paper referenced4 is put forward as an example of raw-food-associated Salmonellosis in cats. Septicaemic salmonellosis was diagnosed post-mortem in two cats. Raw meat eaten by both cats was thought (but not confirmed) to be contaminated with Salmonella serotype Newport. This serotype was isolated from the intestines and lungs of one of the cats. One cat was presented dead, and salmonellosis was diagnosed at post mortem and presumed to be the cause of death. The other was a kitten who was euthanased shortly after a distemper vaccine. The kitten was found to be suffering from "severe, acute, suppurative pneumonia with severe, multifocal, coalescing alveolar and bronchiolar infiltrates."4
The purpose of the fourth paper5 was to summarise the microbiological infections that dogs may acquire through the consumption of raw meat. The authors fingered raw-feeding as a potential public health risk, but they also acknowledged that meat intended for human consumption is routinely contaminated with microbes.
The authors stated that: “Outbreaks of Salmonella-related gastroenteritis in dogs consuming diets containing raw meat are documented.”4 The study which they referenced5 to support this statement compared Salmonella serovars in the diet and feces of a group of racing Greyhounds. The dogs were fed 50-75% of their diet as “Raw meat from rendering plants, which comes primarily from dead, dying, debilitated, and diseased animal”.5 The packages of raw meat were thawed for 24 hours at room temperature and then mixed with supplements prior to feeding. This study is irrelevant to raw feeders who employ common sense, and good hygiene practices (the same as they do when they deal with meat intended for their own consumption). These feeders do not use by-products that are unfit for human consumption, and they do not defrost for 24 hours at room temperature. The study serves as a warning for those wishing to take short cuts with raw feeding.
In keeping with the stance taken by the AVMA, the authors remind us that: “There is also a risk of humans becoming infected with Salmonella spp after handling contaminated meat products intended for dogs.” 5 There is an implication by omission that kibble is a safe option. The many product recalls of Salmonella-tainted kibble prove this is not so.
The authors referenced a study from the New Zealand Medical Journal7 which found that dog ownership was a major risk factor for human Campylobacter infections in Christchurch. No information was supplied regarding the level of raw feeding in these dogs. It would be reasonable to assume that at least the majority of them were kibble-fed. Therefore, this study does not support a claim that raw-feeding, as opposed to kibble-feeding, constitutes a public health risk. To leap to the conclusion that these dogs have been infected by a raw diet would be erroneous, especially given that: “The routes by which dogs can become infected with Campylobacter spp are not precisely known.” 7
In the section on E. coli it was noted that the organism could be found particularly in fresh ground hamburger meats, and that when you feed Greyhounds meat that is contaminated with E. coli, they become ill5. There was no discussion of the prevalence of Escherichia coli in a raw diet appropriate for dogs.
In the section on Yersinia enterocolitica5 the authors noted that: “Household transmission of this pathogen from dogs to people has been documented” and supplied as their reference a case study8 of a group of 21 people in two neighbouring houses who contracted (in two cases, fatally) Yersinia enterocolitica enteritis. There were dogs kept in these households, and there had been some recent diarrhoea in a litter of puppies, however all dogs were destroyed without cultural examination. The houses did not have running water, and relied instead upon wells, and a stagnant pond (which was assumed to be contaminated). While it is possible that the dogs were a source of infection, there was no evidence for this in the original paper, and other obvious potential sources of infection. To conclude that this case study proves household transmission from dogs to people suggest, at the very least, an astonishing inability of the AVMA to interpret literature. No relevance to raw feeding was identified.
In addition to public health risks, risks to the health of dogs were mentioned. “Dogs are susceptible to the neurologic effects of C botulinum toxin, and some packaged foods, such as bacon, are capable of supporting growth of C botulinum and toxin production.”5 Bacon would not be used as part of a well-planned raw diet for dogs.
The final study referenced9 found a variety of coliforms in a group of commercial raw diets. The authors suggested that this created a risk to public health, but as was the case for the other references, they failed to find any evidence for this.
“There is currently inadequate information regarding the safety of raw diets in terms of both animal and human disease. However, considering the variety of infectious and potentially zoonotic pathogens identified here and in other studies, the potential risks must be taken seriously.” 8
Raw pet food is a potential source of pathogenic organisms. So too is processed pet food, along with a great number of products produced for human consumption.
Increasing numbers of dog and cat owners are seeking non-processed and species-appropriate alternatives to kibble and canned foods. They are currently at the mercy of google-searches and internet forums to help them decide how to provide a complete and balanced diet; and how to source and handle food safely. They should be able to look to Veterinarians for sound advice on how best to make these decisions. New Zealand has an opportunity to create a position statement that supports, rather than marginalises, this growing group of pet owners; and that is based on an honest, thorough and erudite evaluation of the scientific literature.
1. Raw or Undercooked Animal-Source Protein in Cat and Dog Diets. https://www.avma.org/KB/Polici... DJ, Schlesinger DP. Preliminary assessment of the risk of Salmonella infection in dogs fed raw chicken diets. Canadian Veterinary Journal 2002;43:441–442.
3. Finley R, ReidSmith R, Weese JS, et al. Human health implications of Salmonella-contaminated natural pet treats and raw pet food. Clinical Infectious Disease. 2006;42:686-691.
4. Stiver SL, Frazier KS, Mauel MJ, et al. Septicemic salmonellosis in two cats fed a raw-meat diet. Journal of the American Animal Hospital Association 2003;39:538–542.
5. LeJune JT, Hancock DD. Public health concerns associated with feeding raw meat diets to dogs. Journal of the American Veterinary Medical Association 2001;219:1222–1225.
6. Muenzenberger, M., Staats, J., Stone, G.G., Chengappa, M.M., Oberst, R.D, Gabbert, N.H., McVey, S., & Hennessy, K.J. Application of Polymerase Chain Reaction for the Correlation of Salmonella Serovars Recovered from Greyhound Feces with Their Diet. Journal of Veterinary Diagnostic Investigations 1993 5: 378
7. Brieseman, M.A. A further study of the epidemiology of Campylobacter jejuni infections. New Zealand Medical Journal. 103(889):207-9, 1990 May 9
8. L. T. Gutman, M.D., E. A. Ottesen, M.D., T. J. Quan, Ph.D., P. S. Noce, M.D., and S. L. Katz, M.D. An Inter-Familial Outbreak of Yersinia enterocolitica Enteritis. New England Journal of Medicine 1973; 288:1372-1377
9. Weese, S.J., Rousseau, J., & Arroyo, L. Bacteriological evaluation of commercial canine and feline raw diets. Canadian Veterinary Journal 2005;46:513–516
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