Risk, raw feeding, and pathogens: a review
Assessing the potential risk involved in feeding dogs raw meat is
Some of the issues I'd like to discuss are assessing the potential
risk of to the dogs, assessing the risk to humans who are around
raw-fed dogs, and the general issue of how to evaluate risks.
References are in parentheses, and a list of sources can be found at
the end of this article, with short excerpts and web links to
full-text or author's abstracts in most cases.
RISKS TO DOGS
First, the issue of risk in feeding a raw diet is not simple. ALL
foods have some degree of risk, so the question isn't whether risk
exists. The question is whether the risk is unacceptable.
You may think you want zero risk - but that's not a choice you get in
life, because all foods carry some type of risk.
Raw meat can indeed be contaminated with e. coli 0157, camphylobacter,
or other pathogens.
However, kibble can also contain disease-causing mold and other
pathogens. Studies by Bueno (2001), Gunsen (2002), and Maia (2002)
found aflatoxin, a toxic mold, in pet food samples. Aflatoxin
contamination of dog kibble resulted in approximately 25 dog deaths
in 1998 (Texas) and vomitoxin was found in batches of Nature's Recipe
kibble in 1995 (Food and Drug Administration, 1995). At least seven dogs
have died from unknown contamination of Petcurean pet food, recalled by the
manufacturer in October 2003 (Syufy, 2003).
Bacteria and mold are not the only risks involved in choosing a food
for your pet. For example, there is some research that says that small
particle size of food is a risk factor in bloat, so with regard to
bloat, feeding large meaty bones would be less risky than feeding any
kibble (Theyse, 1998). Even the packaging of commercial food can carry
some risk, as one study of canned pet foods showed that Bisphenol A,
an industrial chemical and suspected endocrine disruptor leached from
the cans into the food (Kang, 2002).
Dogs are more resistant to most of the common raw meat pathogens than
are humans. (Consider the fact that many dogs use the kitty litter box
as a snack tray without ill effects. Does anyone really want to argue
that cat feces are free of pathogens?) Dogs are resistant - NOT immune
- from the disease potential of these pathogens, and healthy dogs can
harbor them without symptoms. Beutin (1993) found verotoxin producing
e. coli in 4.8% of apparently healthy dogs and Dahlinger (1997)
cultured various types of bacteria, including some forms of e. coli
and salmonella from the lymph nodes of 52% of apparently healthy dogs
brought in for elective spays. Most dogs can eat clean raw meat
without a problem, even if the same raw meat would make humans very sick.
Still, a dog with a compromised immune system or digestive system is
going to be more at risk for illness from any infectious agent than a
dog who is healthy. So I would be reluctant to feed raw meat to an ill
dog, a very young puppy, or a very elderly dog who has not previously
been fed a raw diet.
I recently posted a article to the VETMED list about KSU's studies on
Alabama Rot (a/k/a hemolytic uremic syndrome) in Greyhounds fed raw
meat. (Greyhounds, 1995) Some people immediately posted "atta girl"
posts to me privately. While I have no doubts about the accuracy of
the KSU research, I think most of the readers of VETMED are unaware of
exactly what kind of raw meat is fed to racing greyhounds.
Racing greyhounds are routinely fed raw "4-D meat" as part of their
diet. 4-D meat is unfit for human consumption because the source of it
is animals that died of natural causes (not via normal slaughter
procedures) and includes animals which were diseased, or dying when
they went into the slaughterhouse. This is meat which has either not
been inspected by the USDA or it failed the inspection. This is not
the quality of meat most pet owners buy if they are feeding their pets
raw meat. 4-D meat is very foul stuff, and has the potential to
contain much more in the way of pathogens than the meat that you buy
in the supermarket. I would never feed a dog raw 4-D meat.
I don't know of any published veterinary reports of Alabama Rot in pet
dogs fed raw diets from USDA-inspected meat. It is, unfortunately,
mainly a problem caused specifically by the feeding of unwholesome raw
4-D meat - not raw meat generally.
But raw meat is not alone in having bacterial contamination problems.
There are case reports of pathogens found in commercially produced dog
food and in dog treats such as rawhide, pig ears, jerky, and chew
hooves. (Human, 2000, as well as Clark et al, 2001; White et al. 2003;
Bren 2000; FDA, 2000, Canadian Food Inspection Agency 1999 and
2000). According to the FDA, "all pet chew products of this type may
pose a risk" (FDA, 1999).
So, my personal opinion is that with regard to the dog's health,
feeding USDA graded raw meat to dogs is a reasonable choice for some
owners to make as long as precautions are taken to avoid excess risk
(for example, don't let the meat sit around at room temperature before
giving it to the dog.)
RISK TO HUMANS
Studies of pet dogs have shown e. coli O157 and salmonella in the
feces of pet dogs - but most of these studies were not limited to dogs
fed raw diets. So, kibble fed dogs and dogs fed rawhides, pig ears,
and chew hooves also carry this risk.
However, before getting too fixated on dogs as a source of pathogens
for humans, consider that the most notorious cases of food poisoning
have been caused by poor hygiene from human sources - such as cooks
While undercooked and raw meat is sometimes implicated in food
poisoning cases, there have been an enormous number of cases of
salmonella and e. coli from fruits and vegetables. The seemingly
innocuous bean sprout has been linked to many outbreaks of food
poisoning, as have melons, salads, and apple cider (Health Canada,
2002, and USDA 1995.) In other words, while raw meat is a a risk, so
is almost ANY uncooked food that you eat. There has been one
salmonella outbreak linked to almonds. (Chan et al. 2002)
So, are people at additional risk of getting pathogens from coming in
contact with a dog fed raw meat? There isn't a lot of research that is
directly on topic for this. There are studies of raw-fed dogs (Joffe
and Schlesinger, 2002) but these do not carefully compare the raw fed
dogs to a similar population fed commercial dog food. (See the
commentary on Joffe's study by New n.d.).
I have seen studies of pet dogs that show that food-borne pathogens
were present in a surprisingly large proportion of the dogs tested.
Hackett and Lappin (2003) found infectious agents in the feces of 26%
of healthy Colorado dogs. As far as I can tell, this study was NOT
limited to dogs eating raw diets. Fukata et al (2002) found salmonella
antibodies in 15% of apparently healthy dogs.
I think that you can reduce any potential risk of food poisoning
related to dogs by simply having good hygiene - scrupulously washing
your hands after cleaning up after your dog and washing up thoroughly
before eating. Keeping the dog itself clean probably doesn't hurt,
either. And it would make sense to avoid letting your dog lick you
right after eating a chicken neck. For these reasons, I think that
someone with pets and toddlers might want to avoid raw diets because
small children will not follow the above rules. Kids often will let
the dog lick their face any old time, and they may even try to taste
the dog's meals. (Sato et al. 2000.)
Aside from the concept of 'relative risk' there is the question of
risk versus benefit. If people were completely happy with the health
of dogs from kibble feeding, the entire "raw foods" movement would
have never taken root. There's nothing more convenient than pouring
kibble into a dish. So some people must be seeing a benefit from
I think that most veterinarians' assessment of risk from raw diets is
skewed by the fact that normal, healthy dogs are not generally seen by
vets, and that most nutrition research is done using commercial diets.
If there is a large population of totally healthy dogs eating raw
diets, they may never be noticed by a veterinarian. On the other hand,
vets will usually see the dogs who got the 3-day old chicken bones
from the garbage can, or the one whose owner misguidedly thought it
was a good idea to give their dog the skin and bones from their
Raw diets do carry risk. These can be reduced by feeding the freshest
cleanest meat the owner can buy and following all the rules about
temperature, storage and hygiene (FSIS, 1999).
Kibble diets and dog treats also carry risk - and these can be reduced
by buying fresh and high-quality food, rather than the cheapest stuff
available, and by following proper storage and hygiene rules. But it's
worth noting that some of the priciest brands of kibble were recalled
because of toxic contamination, so a high price does not ensure safety.
I don't think there is one right way to feed dogs. I think that
careful attention to nutrition and hygiene reduce the risk associated
with whatever feeding regimen you choose. It's interesting to note
that feeding raw meat is intensely controversial, while feeding pig
ears and jerky - which carry similar if not higher risks for
contamination - is widely accepted as reasonably safe.
Incidentally, in case anyone is wondering, the main diet for my dogs
is free-fed kibble. I free feed because it helps prevent gluttony, and
I have never had a case of bloat in Greyhounds, which are a somewhat
bloat-prone breed. I also routinely feed my dogs raw chicken parts. I
feed bony chicken parts because I have found this to be the most
effective way of keeping my dogs' teeth clean. I haven't noticed any
other big change in their health, but they love the chicken parts and
their teeth are clean and their breath sweet as a result. Greyhounds
are notorious for foul teeth as they age, but even my oldest dog has
remarkably clean teeth.
With regard to the risk, I can only share my experience, in that I've
not seen any illnesses in the dogs I can attribute to the raw meat nor
to the kibble. I made my choice because I know of more pet greyhounds
that have died from the anesthesia involved in teeth cleaning and
other elective surgeries than have died from eating a raw diet.
I wrote this article to seriously examine the question a VETMED
subscriber asked about the potential for risk when using raw-fed dogs
as therapy dogs. As long as the dogs aren't fed raw meat during
therapy sessions, I don't see a problem. While these dogs may carry
pathogens, so may dogs fed kibble or pig ears, or rawhide. One survey
found salmonella contamination of 41% of the dog treats examined
(White et al, 2003). Accordingly, it would be not be logical or fair
to bar raw fed dogs from a therapy dog program, unless you are also
barring all dogs who are fed pig ears, rawhides, and other similar treats.
Beutin L, Geier D, Steinruck H, Zimmermann S, Scheutz F. (1993).
Prevalence and some properties of verotoxin (Shiga-like
toxin)-producing Escherichia coli in seven different species of
healthy domestic animals.
Journal of Clinical Microbiology, 31(9):2483-8.
"Fecal samples from 720 healthy, domestic animals representing seven
different species (cattle, sheep, goats, pigs, chickens, dogs, and
cats) were investigated for verotoxin (VT [Shiga-like
toxin])-producing Escherichia coli (VTEC). VTEC were isolated from 208
animals (28.9%), most frequently from sheep (66.6% VTEC carriers),
goats (56.1%), and cattle (21.1%). VTEC were isolated less frequently
from pigs (7.5%), cats (13.8%), and dogs (4.8%) and were not found in
chickens (< 0.7%)."
Bren, L (2000, November).
Pet treats can make you ill.
FDA Veterinarian, 15(5).
"Pet treats made from the dried ears, hooves, lungs, and bones of pigs
and cows have been implicated in Salmonella poisoning in humans."
Bueno DJ, Silva JO, Oliver G. (2001).
Mycoflora in commercial pet foods.
Journal of Food Protection, 64(5):741-3.
"This article reports on the identification of mycoflora of 21 dry pet
foods (12 belonging to dogs and 9 to cats) that corresponded to 8
commercial brands [...] Some genera and species isolated and
identified from the foods analyzed are potentially producing toxins,
which are known as mycotoxins. This involves a risk for animal health."
Canadian Food Inspection Agency (1999).
Food Recall Archives.
9/24 - "Presence of Salmonella bacteria in pig ear dog treats" [Farm
9/25 - "Possible presence of salmonella bacteria in EURO-CAN PIG EAR
and other dog treats"
10/12 - "Presence of salmonella bacteria in dog treats" [Rollover,
Co-op, PC, and Safeway]
11/19 - "Presence of Salmonella bacteria in certain UNCLE SAM'S brand
dog treats" [Sargeant's Pet Products]
11/19 - "Presence of Salmonella bacteria in certain rawhide dog
treats" [Avant RawHide]
12/1 - "Possibility of Salmonella bacteria in JAWBONE brand roasted
12/6 - "Presence of Salmonella bacteria in ROLLOVER brand dog treats"
12/7 - "Presence of Salmonella bacteria in dog treats." [Co-op Gold
and President's Choice]
Canadian Food Inspection Agency (2000).
Food Recall Archives.
3/1 - "HEALTH HAZARD ALERT - Dog treats may contain Salmonella."
Chan ES, Aramini J, Ciebin B, Middleton D, Ahmed R, Howes M, Brophy I,
Mentis I, Jamieson F, Rodgers F, Nazarowec-White M, Pichette SC,
Farrar J, Gutierrez M, Weis WJ, Lior L, Ellis A, Isaacs S. (2002).
Natural or raw almonds and an outbreak of a rare phage type of
Salmonella enteritidis infection.
Canadian Communicable Diseases Report, 28(12):97-9.
Clark C, Cunningham J, Ahmed R, Woodward D, Fonseca K, Isaacs S, Ellis
A, Anand C, Ziebell K, Muckle A, Sockett P, Rodgers F (2002).
Characterization of salmonella associated with pig ear dog treats in
Journal of Clinical Microbiology, 39(11):3962-8.
Dahlinger J, Marks SL, Hirsh DC (1997).
Prevalence and identity of translocating bacteria in healthy dogs.
Journal of Veterinary Internal Medicine, 1997 Nov-Dec;11(6):319-22.
European Commission (1998, October 30).
Report of the Scientific Committee on Veterinary Measures relating to
Public Health (SCVPH) on Benefits and Limitations of Antimicrobial
Treatments for Poultry Carcasses.
FDA - Food and Drug Administration (2000).
Nationwide Recall of Medalist Brand Pig Ear Treats Due to Possible
HHS News May 23, 2000.
"Treat Makers, L.L.C., a manufacturer of natural pet treats, is
voluntarily recalling Medalist brand pig ear pet treats, lot numbers
07600EXU3 and 08300EXU1, due to possible contamination with
Salmonella. Pet owners can become ill by touching their mouth or food
without washing their hands after handling the pet treats."
FDA - Food and Drug Administration (1999).
FDA Issues Nationwide Public Health Advisory about Contaminated Pet Chews.
HHS News October 1, 1999.
"The Food and Drug Administration today issued a nationwide public
health warning alerting consumers about a number of recent cases in
Canada of human illnesses apparently related to contact with dog chew
products made from pork or beef-derived materials (e.g., pigs ears,
beef jerky treats, smoked hooves, pigs skins, etc.). [...] Initial
reports of illnesses came from Canada and involved Canadian products,
but subsequent examination of similar products produced in the U.S.
indicate that all pet chew products of this type may pose a risk."
Food and Drug Administration (1995).
Recalls and Field Corrections: Veterinary Products -- Class II
FDA Enforcement Report, Oct. 11, 1995.
"Product: Nature's Recipe Pet Food (dry) in 5, 20, and 40 pound paper
bags (canine) and 4, 8, and 20 paper bags (feline) [...] Products are
adulterated with the micotoxin vomitoxin, which may cause dogs and
cats to become ill (vomiting and/or diarrhea)."
FSIS - Food Safety and Inspection Service, U.S. Dept. of Agriculture
The Poultry Label Says "Fresh"
Fukata T, Naito F, Yoshida N, Yamaguchi T, Mizumura Y, Hirai K (2002).
Incidence of salmonella infection in healthy dogs in Gifu Prefecture,
Journal of Veterinary Medical Science, 64(11):1079-1080.
Greyhounds Provide Model for E. Coli Food Poisoning in Humans (1995).
K-State Press Release, December 1995.
Gunsen U, Yaroglu T (2002).
Aflatoxin in dog and horse feeds in turkey.
Veterinary and Human Toxicology 44(2):113-4.
"Aflatoxin levels were determined by ELISA in 18 dog and 20 horse feed
samples, collected from different firms from June 2000 to June 2001 in
Turkey. The minimum and maximum levels of total aflatoxin in the dog
and horse feeds were <1.75-20 microg/kg and <1.75-14 microg/kg,
respectively; 3/18 dog feed samples (16.7%) and 2/20 horse feed
samples (10%) exceeded the Turkish tolerance limit of 10 microg/kg in
food or feed."
Hackett T, Lappin MR (2003).
Prevalence of enteric pathogens in dogs of north-central Colorado.
Journal of the American Animal Hospital Association, 39(1):52-6.
"Infectious agents potentially associated with gastrointestinal
disease were detected in 34 of 130 (26.1%) fecal samples. Agents with
zoonotic potential were detected in feces from 21 (16.2%) of 130 dogs
and included Giardia spp. (5.4%), Cryptosporidium parvum (3.8%),
Toxocara canis (3.1%), Salmonella spp. (2.3%), Ancylostoma caninum
(0.8%), and Campylobacter jejuni (0.8%). Positive test results
occurred in dogs with or without gastrointestinal signs of disease."
Health Canada (2002).
Risks Associated with Sprouts
"Worldwide between 1995 to 2001, there have been 13 outbreaks of
foodborne illnesses linked to sprouts. In most instances, the
illnesses were caused by either Escherichia coli (E. coli) O157:H7 or
"Anyone who eats raw sprouts is at risk for exposure to E. coli
O157:H7 or Salmonella bacteria. However, the risk of serious health
effects is greater for young children, seniors, and people with weak
Human Health Risk from Exposure to Natural Dog Treats (2000).
Canadian Communicable Disease Report 26(06):41-42.
"In August 1999, the province of Alberta reported an increase in
Salmonella Infantis cases. The initial investigation conducted by the
regional public-health authority of Calgary, Alberta, demonstrated
that eight of 12 S. Infantis cases were dog owners, and that nine of
12 had had exposure to pig ear dog treats."
Joffe DJ, Schlesinger DP (2002).
Preliminary assessment of the risk of Salmonella infection in dogs fed
raw chicken diets.
Canadian Veterinary Journal, 43(6):441-2.
"Salmonella was isolated from 80% of the BARF diet samples (P < 0.001)
and from 30% of the stool samples from dogs fed the diet (P = 0.105).
Dogs fed raw chicken may therefore be a source of environmental
Kang JH, Kondo F (2002).
Determination of bisphenol A in canned pet foods.
Research in Veterinary Science, 73(2):177-82.
"The concentration of BPA ranged from 13 to 136 ng/g in canned cat
food and from 11 to 206 ng/g in dog food."
Maia PP, Pereira Bastos de Siqueira ME (2002).
Occurrence of aflatoxins B1, B2, G1 and G2 in some Brazilian pet foods.
Food Additives and Contaminants, 19(12):1180-3.
"One hundred food samples (45 for dogs, 25 for cats, 30 for birds)
were collected at random from pet shops in Alfenas city, south-east
Brazil. [...] Aflatoxins were detected in 12.0% of the samples."
New, L. (n.d.)
Salmonella and the raw diet.
Mountain Dog Food website [viewed on 16Nov03].
Sato Y, Mori T, Koyama T, Nagase H (2000).
Salmonella virchow infection in an infant transmitted by household dogs.
Journal of Veterinary Medical Science, 62(7):767-9.
Syufy, F (2003).
Go! Natural Pet Foods Recall: Canadian company recalls all products
manufactured in Texas.
About.com October 26, 2003.
Texas Agricultural Experimental Station, Office of the State Chemist (1998).
Dog Food Recall. November 2, 1998.
"Doane Products Company announced today a recall of dry dog food
produced between July 1 and August 31, 1998, at its Temple, Texas
plant. [...] Doane officials said a veterinary diagnostic laboratory
has attributed the deaths of approximately 25 dogs to aflatoxins.
Aflatoxins result from a naturally occurring mold which at high levels
can cause liver damage. The mold may be more likely to occur in corn
that has been subjected to extreme weather conditions."
Theyse LF, van de Brom WE, van Sluijs FJ (1998).
Small size of food particles and age as risk factors for gastric
dilatation volvulus in great danes.
Veterinary Record, 143(2):48-50.
"Dogs fed a diet containing particles of food > 30 mm in size (kibble
and/or dinner and/or home-prepared food with large pieces of meat) had
a lower risk of GDV than dogs fed a diet containing only particles < 30 mm
in size (kibble or dinner and/or canned meat and/or home-prepared food
cut into small pieces or ground in a food processor)."
USDA - U.S. Dept. Of Agriculture, Food Safety and Inspection Service (1995).
An outbreak of e. coli O157:H7 How could it happen?
Food Safety and Inspection Service Flyer, July 1995.
"Illness from the O157:H7 bacteria has been caused by foods including
undercooked ground beef, roast beef, raw milk, improperly processed
cider, contaminated water, mayonnaise, cantaloupes, vegetables grown
in cow manure and salami (a dry sausage). Outbreaks have also started
in cross-contamination at food service outlets--delicatessens, grocery
carryouts and salad bars"
White DG, Datta A, McDermott P, Friedman S, Qaiyumi S, Ayers S,
English L, McDermott S, Wagner DD, Zhao S (2003).
Antimicrobial susceptibility and genetic relatedness of Salmonella
serovars isolated from animal-derived dog treats in the USA.
Journal of Antimicrobial Chemotherapy, 52(5):860-3.
"A total of 158 dog treats derived from pig ears and other animal
parts were randomly collected nationwide and assayed for the presence
of Salmonella. [...] Forty-one percent (65/158) of samples were
positive for Salmonella. [...] CONCLUSIONS: The study indicates that
animal-derived dog treats in the USA could be a potential source of
animal and human infections with Salmonella, including
multidrug-resistant Salmonella strains."
Willis C (2001).
Isolation of Salmonella species from imported dog chews.
Veterinary Record, 149(14):426-7.
Copyright 2003, Stacy Pober. All rights reserved.
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(Revised slightly, 7 Dec 2003).