This is the final installment of answers to the questions and comments posted by readers of my feature series "It's A Dog's Breakfast."Developing immunity to Salmonella infections
One reader asked whether repeated exposure to Salmonella in food would increase the resistance of a person or a dog to infection. In theory, the answer should be “Yes”. In practice, this might not occur – or might be only partially effective, at best.
There are at least 2,000 strains of Salmonella, many of which are immunologically distinct from each other. Resistance to one strain might confer at least partial resistance to other closely-related strains, but not to strains that are less closely related. This is an ongoing problem for researchers who are trying to develop Salmonella vaccines for cattle and poultry.
The following articles illustrate the complexity of the immune system and its response to Salmonella.
- Clare, S., et al. 2003. Intracellular adhesion molecule 1 plays a key role in acquired immunity to salmonellosis. Infection and Immunity, Vol. 71, No. 10, pp. 5881-5891.
- Mastroeni, P., and N. Ménager. 2003. Development of acquired immunity to Salmonella. Journal of Medical Microbiology, Vol. 52, pp. 453-459.
- Mittrucker, H.W., and S.H. Kaufmann. Immune response to infection with Salmonella typhimurium in mice. Journal of Leukocyte Biology, Vol. 67, No. 4, pp. 457-463
The importance of good food-handling and sanitation practices
This is fundamental to all food preparation - human and animal. In my opinion, attention to proper food handling practices can mitigate, but not eliminate, the risk of feeding a raw diet.
Accessing “Food Safety: Old Habits, New Perspectives”
Google Books offers free access to portions of my book. To take advantage of this access, go to Google Books Advanced Search, type the title of the book in the Title Search box and hit the “return” key on your computer keyboard. You can then either browse some pages of the book or search for specific topics.
My book is also available in at least 180 academic and government libraries world-wide. To find the library nearest you, go to WorldCat, enter your city or zip code and hit the “return” key.
My credentials
Several readers asked for more details about my professional background and credentials. I am a graduate of McGill University (Honours BSc. in Microbiology and Immunology) and the University of Toronto (MSc. in Mycology). I am a Past President of the Canadian College of Microbiologists. Here are a few of the things I have done in my 35+ years as a microbiologist:
- written two books on food microbiology;
- written more than 20 research articles, all of which were published in various peer-reviewed journals;
- addressed an annual meeting of the Japanese Society of Food Microbiology at the invitation of the Japanese government;
- developed and edited a special Salmonella section for the Journal of AOAC International at the invitation of the Journal’s Managing Editor;
- served on the Editorial Board of Food Protection Trends, a publication of the International Association for Food Protection; and
- wrote sub-chapters for The Wiley Encyclopedia of Food Science and Technology, the Encyclopedia of Food Microbiology, and the Compendium of Methods for the Microbiological Examination of Foods.
In Summary
In this series of articles, I have addressed several unsubstantiated claims that appear on web sites and in discussion forums about the safety and benefits of feeding raw food. The purported nutritional benefits of feeding a raw diet are still unproven. Quite simply, no scientifically rigorous nutritional studies have been published to support – or contradict – the claims.
In discussing the safety issues, I have provided links to peer-reviewed scientific research reports and other authoritative sources to support the following statements:
- dogs can carry Salmonella asymptomatically and can pass the microbe in their feces;
- dogs that are fed a diet that is contaminated with Salmonella have a higher probability of carrying Salmonella than dogs that are fed a Salmonella-free diet;
- raw diets have a higher likelihood of being Salmonella-contaminated than home-cooked diets or than processed diets, such as kibble;
- dog saliva cannot reliably inactivate Salmonella or prevent the Salmonella from reaching the dog’s intestinal tract; and
- people can become infected with Salmonella – and other pathogens – through contact with an infected animal.
The Bottom Line
Feed your dog a raw diet if you feel you must. But do so with full knowledge and appreciation of the possible consequences.
Posts
I came across your excellent series of postings while trying to decide whether to feed my new Irish Wolfhound puppy a raw diet, as strongly recommended by the breeder.
ReplyDeleteLet's assume that I have concluded, despite understanding the food safety issues from the canine perspective, that the benefits to the dog of feeding raw outweigh the potential risks to the dog. I may not have in fact concluded that yet, but let's not muddy the waters with that issue for the moment.
Let'a also assume that I will be conscientous about managing the dog's feces and ensuring that there is no canine to human infection by that source. And to dispose of another issue, let's also assume that our food handling is of sufficient quality to minimize the risk of human infection while preparing and serving the dog's meals.
My real question, then, concerns the risk of canine to human infection from casual non-fecal contact. For example, if I feed the dog raw chicken backs that turn out to carry salmonella or e. coli, he uses his paws to hold them while he eats them, and his beard also comes into full contact with the raw chicken, what is the potential of infecting humans from later contact with the paws, the beard or the dog's tongue? If there is some risk, is there any realistic way of managing it? I'd like to try a raw diet, but not at the expense of infecting a family member with salmonella or e.coli.
Thanks.
Glenavy, you raise a very important question. Some raw feeders mitigate the risk by wiping their dogs paws, beards and faces with vinegar. An antiseptic baby wipe would be another possibility. Note that I said "mitigate" not solve. These are not 100% effective solutions, but they will reduce the risk of contamination.
ReplyDeleteKeep in mind, though, that there's no reliable way to disinfect your dog's mouth (including tongue). If your puppy has residual Salmonella on his/her tongue and licks a child, the bacteria could be transferred. Likewise, dogs lick their various body parts, which can also transfer the bacteria.
To minimize the risk of human infection, you and your family will have to be scrupulous in attending to hand- and face-washing after handling/being licked by your pet.
Having said all of this, many people handle the raw feeding successfully. Each family's situation is different.
Good luck, and I hope you will continue to find my blog useful.
Phyllis