The Question of Bacteria

Raw foodists believe eating only raw food, including raw meat, is normal. When it comes to feeding pets, what could be more natural for carnivores than a raw meaty diet?

The pet food industry has only been around for less than one hundred years, whereas carnivores have been thriving and reproducing on raw foods for many, many thousands of years. All foods have some degree of risk. Raw meat can be contaminated with bacteria; however, kibble can also contain disease-causing molds and other pathogens. Aflatoxin contamination of dog kibble has resulted in hundreds of sick pets and even death. As well, 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.

Dogs and cats evolved to eat bacteria in their food and from other sources in the environment. They eat soil, contaminated meat, and buried carcasses and bones. Dogs being naturally coprophagic enjoy eating the feces of many different animals and much to their owner’s disgust, sometimes their own. Consider that many dogs use the kitty litter box as a snack without adverse effects. Domestic dogs and cats scavenge and sniff around in all sorts of 'unhygienic' places. Not only that, they continue the ancient ritual of licking mouths, and genitals; both their own and those of others of their species. Each one of these anatomical areas is a source of bacteria. So, no matter what the diet, by licking its "private parts", your dog or cat is consuming bacteria.

Protective Activities of the Digestive System

There are a number of factors that prevent pathogenic bacteria from taking a foothold in the dog or cat’s body. The first defense is saliva which kills bacteria entering with the food. Saliva is often referred to as a gatekeeper because of its protective role against harmful pathogens.

The stomach is highly acid (pH 1-2) and contains strong hydrochloric acid (HCL). HCL creates the right pH for enzymes to work efficiently and it kills bacteria that have escaped the protective enzymes in the saliva. Bacteria that survive the high acid content of the stomach then pass into the small intestine. Compared to the stomach, the small intestine is a relatively hospitable environment. The first section of the small intestine is called the duodenum. The pancreas and liver deposit their digestive enzymes, bicarbonate and bile salts, respectively, in this part of the small intestine.

The digestive enzymes from the pancreas digest the cells walls of harmful bacteria. The bile salts from the liver are primarily used for fat digestion and transportation and also potent antimicrobial agents. In addition, lysozyme is secreted by cells that line the digestive tract. Lysozyme is a potent enzyme that attacks bacterial cell walls and is believed to be another primary control preventing bacterial overgrowth in the upper gastrointestinal tract.

Bacteria that are able to survive need to be able to stick to the lining of the intestinal wall. To hold on they must contain adhering proteins, have their own means of locomotion, and be able to multiply rapidly enough to overcome the forward peristaltic movements of the small intestine. Bacteria that fail to meet the criteria for attachment, motility, and propagation will pass on into the fecal matter and into the large intestine. The large intestine collects and processes undigested material that passes through the small intestine. The bacterial population of the large intestines is much greater than that found in the small intestine, with a higher number of gram-negative bacteria. These bacteria are very important to normal large intestinal physiology.

Normal Flora

The term "normal flora" implies that bacteria exist within the animal body symbiotically and generally cause no harm. Each dog or cat’s diet, environment, body chemistry, and immune system influence their particular floral balance.

The intestinal flora is relatively stable and maintains fairly constant numbers and types of bacteria in each area of the intestinal tract. This stability of normal flora discourages infection by outside pathogens and prevents overgrowth of potentially pathogenic members. New organisms that enter the system in contaminated food or water generally are suppressed by the established flora. This suppression is related to production by members of the resident flora of antimicrobial substances which inhibit the growth of foreign microorganisms. Antibiotics that kill off part of the intestinal flora can upset its balance and may open the door to infection or pathologic overgrowth. For instance, normal dogs and cats are quite resistant to Salmonella, and a large oral dose is required to initiate infection. If the intestinal flora is suppressed by antibiotics, however, the individual becomes much more susceptible and can be infected by a relatively small dose.

Do raw diets carry bacteria?
Yes, studies have concluded that raw pet foods contain bacteria. However, the fact that bacteria are present should not come as a surprise. There is simply no such thing as "bacteria-free" meat. Most of the 10 billion cows, pigs, and birds butchered every year for meat at the supermarket are contaminated with one bacteria or another. Therefore, it is probable that the meat you bring into your home to feed yourself or your family is potentially as contaminated with bacteria as raw meats fed to pets! For example, Salmonella spp. has been identified from 7.5% of ground beef, 44.6% of ground chicken, and 49.9% of ground turkey samples.

“Meat from healthy animals becomes contaminated at slaughter. Meat surfaces become infected with microorganisms associated with food poisoning during handling, packaging, processing, storage, and transportation. 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 products should be considered contaminated.” Rebecca L. Remillard, Ph.D., DVM

What about the people handling feces from animals fed raw diets?
Naysayers say: “For humans, the risk of exposure to pathogens via direct or indirect contact with animal feces, or via contact with raw diets, must be considered, particularly with Salmonella spp., as fecal shedding of Salmonella spp. present in diets has been identified in dogs.”

Since its unlikely you will be sharing your pet’s raw diet at mealtime, any transmission of bacteria would likely occur through the fecal-oral route. For instance, bacteria might get on your hands while picking up your dog or cat’s feces or when coming into contact with your pet’s anal area when lifting it up. In reality, you’d literally have to eat the animal’s feces to get enough salmonella from it to make you sick. The solution? Abstain from eating dog or cat feces (that should be easy!), ensure appropriate hygiene such as hand washing after handling pets, cleaning the cat’s litter box or picking up dog feces. Immediately picking up and disposing of feces eliminated by your pet in public areas reduces risks associated with environmental contamination. It’s interesting to note that while feeding raw meat is somewhat controversial, pig ears, pizzles and rawhide - which carry similar if not higher risks for contamination - is widely accepted as reasonably safe. One survey found salmonella contamination of 41% of the dog treats examined.

Can people become infected with food-borne pathogens when handling contaminated meat products?
Naysayers say: “Bacterial contamination of surfaces that have been in contact with raw diets has not been evaluated, but must be considered. Bacterial contamination of pet food bowls may be a potential source of infection for humans.”

Why is it that veterinarians think pet owners are dummies when it comes to handling raw foods for pets? Unless you are a strict vegetarian, you handle and prepare raw meat in your kitchen so what is the difference between the raw meat consumed by yourself or your pet? Nothing!

Good hygiene in the kitchen is mandatory whether you are preparing food for yourself, your family or your pet. Keep shelves, counter tops, refrigerators, freezers, utensils, sponges, and towels clean to prevent bacterial contamination of food at home. It is especially important to wash all utensils and your hands with soap and hot water after handling one food and before handling another. This helps prevent cross-contamination in which, for example, bacteria in raw meat could be transferred to other foods, such as vegetables. Use a different board for cutting different foods such as produce and meat. Wash cutting boards with hot, soapy water after each use; then rinse and air dry or pat dry with fresh paper towels. Non-porous acrylic, plastic or glass boards and solid wood boards can be washed in an automatic dishwasher. (Laminated boards may crack and split.) Sanitize both wooden and plastic cutting boards with a solution of one teaspoon liquid chlorine bleach per quart of water. Flood the surface with the bleach solution and allow it to stand for several minutes, then rinse and air dry or pat dry with fresh paper towels.

Bacteria Are Everywhere

People that are paranoid about bacteria in raw pet diets need not be! Bacteria live all around us and within us. The air is filled with bacteria. Bacteria live in the deepest parts of the ocean and deep within Earth. They are in the soil, in our food, and on plants and animals. Even our bodies are home to many different kinds of bacteria. Our lives are closely intertwined with bacteria, and the health of our planet depends very much on their activities.

You can avoid bacteria by not feeding pets raw foods, but then don't use a public restroom. When you turn off the water tap or pull open the door to leave a restroom, you'll contaminate clean hands. Women’s public restrooms contain twice as much fecal bacteria as men’s, probably because women are often accompanied by small children and babies in need of a change. All this applies to your own bathroom. Each time that it's flushed, your toilet propels invisible bacterial and viral aerosols into the air that can float for up to 2 hours contaminating everything from hand towels to toothbrushes.

Have you opened a door in a public place today? Ridden an escalator? Worked out at the gym, bought a soda from a vending machine or shopped for groceries? Studies show that shopping cart handles are among the leading sources of germs and bacteria in public. Microbiologists at the University of Arizona Environmental Research Laboratory found 21% of shopping carts tested to contain bodily fluids. The handles can harbor staphylococcus aureus, Streptococcus pneumoniae, E coli and other bacteria from meat and poultry.

The University of Arizona published some research a few years ago. They found that almost a third of the railings in public transportation-on buses or subways-were infected with the same bacteria that is found in feces and that 25% of the seats in movie theatres were infected with E.coli bacteria, which is bacteria from feces. Another study by U.S. Air Force doctors in Ohio found that money harbors bacteria which can make both immuno-suppressed and healthy people very sick.

What is the worst offender in the kitchen? The kitchen sponge or dishcloth! Both are the perfect nurturing environment for bacteria. The next worst offender is the kitchen sink. Feel the need to get away from this story and take a little coffee break? You might want to hold off on that plan: Twenty percent of the coffee cups tested in one study were oozing with bacteria, thanks to the sponges that clean them.

It is generally well known that toilets and kitchens are high-risk areas for germ growth, but laundry is rarely mentioned as a potential source of contamination. Research has shown that germs can spread from one fabric to another and from the washing machine drum to the next load. For years it has been accepted that very hot water is necessary to kill bacteria in the washing, but the preservation of modern textiles has led to the use of ever lower temperatures and, in our efforts to consume less energy, our environmental concerns have also led to a reduction in washing powder. The way that we do our washing today is not always sufficient to destroy bacteria in clothes. Bacteria from food, the body or other sources can survive a wash cycle and spread via our hands to other surfaces. Among them are staphylococcus aureus and klebsiella pneumoniae and E coli.

Antibacterial soaps would be good if they worked, but they don’t seem to do anything. Disinfectants, on the other hand, kill both viruses and bacteria. Chlorine bleach, alcohol, and hydrogen peroxide are all good disinfectants.

Here are some interesting tidbits about hand washing and spreading germs: 95 percent of people say they wash their hands after using a public bathroom, but only 67 percent actually wash their hands. Only 33 percent of those who do wash their hands use soap. And only 16 percent really wash their hands long enough. Every three minutes, a child brings his hand to his nose or mouth. Every 60 seconds, a working adult touches as many as 30 objects. (If you’re traveling, by the way, you might want to disinfect that remote control for the TV. That’s where the big bacteria boys hang out in a hotel room. Some viruses can survive on surfaces for up to 72 hours.)

Speaking of working adults, the phone comes out as the grimiest object of bacteria in the office, followed by the desktop, keyboard, mouse, fax machine, and photocopier. Where are the least germs in the office? By now, you should have guessed: the toilet seat. But, there are a hundred times more bacteria on a cutting board than a toilet seat, so lick a toilet seat rather than a cutting board.

Many insects such as flies, wasps, and cockroaches carry food poisoning bacteria on their legs and bodies and contaminate food and work surfaces when they walk on them. Rodents (rats and mice) excrete bacteria in their feces which can also result in contaminated food and surfaces in supermarket warehouses - the very food items you bring into your home.

Food Contamination
People usually associate raw meat with bacterial contamination. However, meat isn't the only source of bacteria. Did you know you should observe the same handling and preparation methods for vegetables and fruits as used with raw meat? I'll bet not. Raw fruits and vegetables can become contaminated along the farm-to-table continuum. Produce used for salads - lettuce and spinach, for example - grow low to the ground, where they are likely to come in contact with contaminated fertilizers. Sometimes they’re irrigated with contaminated waters or picked by workers with poor hygiene practices. The complex, multi-layered surfaces of salad produce are more difficult to clean after picking than produce with a smooth surface, such as apples or potatoes. Because fresh fruits and vegetables are usually eaten raw, they can pose a health risk if they’re not properly handled. Therefore, all produce needs to be thoroughly washed and safely prepared and handled before it is eaten. Even then, the bacterial population on fruits and vegetables is reduced but not eliminated. Pathogens associated with vegetables and fruits includes Cryptosporidium, parasite (juice/cider and produce), Cyclospora, parasite (produce), Escherichia coli O157:H7 (juice/cider and produce), Norwalk Virus (produce), Salmonella (juice and produce), Shigella (produce).

The growth of many kinds of bacteria can be reduced or stopped by refrigeration and freezing-two important practices in the preservation of food, including milk. However, refrigeration alone will not kill bacteria. This is best illustrated by the fact that at normal refrigerated temperatures, milk will still, in time, turn sour. The maximum allowable number of bacteria (SPC) in milk to be marketed for human consumption is in the range of 100,000 bacteria per milliliter (about 10 drops) of milk. Some dairy producers are satisfied with any bacteria count so long as they can market their milk.

Okay, so no milk. Are you thinking juice may be a better and safer alternative? Ninety-eight percent of the juice sold in supermarkets is pasteurized when fruits and vegetables are fresh-squeezed, harmful bacteria from the outside of the produce can become a part of the finished product. If it’s ingested, children, the elderly, and people with weakened immune systems risk serious illness. E. coli O157:H7 is very resistant to acid, so it can survive in an acidic medium like orange or apple juice for a long time.

Since the U.S. Food and Drug Administration (FDA) issued its first warning about the safety of raw sprouts, there has been a growing controversy about this issue. On the one hand, sprouts have some well-documented health benefits. On the other hand, however, ingestion of sprouts contaminated with the bacterium E. coli O157:H7 caused the death of 17 persons in Japan in 1996 and was also responsible for illness in over 6,000 persons. This outbreak factored into the U.S. FDA decision in 1999 to issue a warning about the dangers of eating raw or lightly cooked sprouts and recommending cooking of all sprouts to lower risk of infection. The FDA specifically mentioned alfalfa, clover, and radish sprouts in this initial warning. In 2002, it included mung bean and alfalfa sprouts in a renewed warning about consumption of these foods.

Who Should Avoid Eating Dry Sausages? Because dry sausages are not cooked, the elderly, very young children, pregnant women and those with weakened immune systems might want to avoid eating them. The bacterium E. coli O157:H7 has been found to survive the process of dry fermenting.

Factory farmed eggs can carry salmonella. Most tainted eggs are contaminated within the hens' ovaries before their shells form. Washing the eggs before cracking them open is no guarantee that they'll be free of bacteria. Therefore, it's best to avoid anything containing raw or undercooked eggs, including raw cookie dough, cake batter, eggnog, hollandaise sauce and Caesar salad or other dressings made with raw eggs. It is estimated that one out of every 50 consumers is exposed to a contaminated egg yolk each year.

Bacteria Responsible for Human Food-borne Illness

To help keep things in perspective consider that there are many, many sources of bacterial contamination and although some bacteria cause more serious illness than others, only a few are responsible for the majority of cases. The following are the nine most prominent bacteria that affect humans:

Campylobacter jejuni
Found: intestinal tracts of animals and birds, raw milk, untreated water, and sewage sludge.
Transmission: contaminated water, raw milk, and raw or under-cooked meat, poultry, or shellfish.
Symptoms: fever, headache, and muscle pain followed by diarrhea (sometimes bloody), abdominal pain and nausea that appear 2 to 5 days after eating; may last 7 to 10 days.

Clostridium botulinum
Found: widely distributed in nature: in soil and water, on plants, and in intestinal tracts of animals and fish. Grows only in little or no oxygen.
Transmission: bacteria produce a toxin that causes illness. Improperly canned foods, garlic in oil, and vacuum-packaged and tightly wrapped food.
Symptoms: toxin affects the nervous system. Symptoms usually appear within 18 to 36 hours, but can sometimes appear within as few as 4 hours or as many as 8 days after eating; double vision, droopy eyelids, trouble speaking and swallowing, and difficulty breathing. Fatal in 3 to 10 days if not treated.

Clostridium perfringens
Found: soil, dust, sewage, and intestinal tracts of animals and humans. Grows only in little or no oxygen.
Transmission: called “the cafeteria germ” because many outbreaks result from food left for long periods in steam tables or at room temperature. Bacteria destroyed by cooking, but some toxin-producing spores may survive.
Symptoms: diarrhea and gas pains may appear 8 to 24 hours after eating; usually last about 1 day, but less severe symptoms may persist for 1 to 2 weeks.

Escherichia coli O157:H7
Found: intestinal tracts of some mammals, raw milk, unchlorinated water; one of the several strains of E. coli that can cause human illness.
Transmission: contaminated water, raw milk, raw or rare ground beef, unpasteurized apple juice or cider, uncooked fruits, and vegetables; person-to-person.
Symptoms: diarrhea or bloody diarrhea, abdominal cramps, nausea, and malaise; can begin 2 to 5 days after food is eaten, lasting about 8 days. Some, especially the very young, have developed Hemolytic Uremic Syndrome (HUS) that causes acute kidney failure. A similar illness, thrombotic thrombocytopenic purpura (TTP), may occur in older adults.

Salmonella (over 1600 types)
Found: intestinal tract and feces of animals; Salmonella enteritidis in raw eggs.
Transmission: raw or undercooked eggs, poultry, and meat; raw milk and dairy products; seafood.
Symptoms: stomach pain, diarrhea, nausea, chills, fever, and headache usually appear 6 to 48 hours after eating; may last 1 to 2 days.

Streptococcus A
Found: noses, throats, pus, sputum, blood, and stools of humans.
Transmission: people-to-food from poor hygiene, ill food handlers, or improper food handling; outbreaks from raw milk, ice cream, eggs, lobster, salads, custard, and pudding allowed to stand at room temperature for several hours between preparation and eating.
Symptoms: sore throat, painful swallowing, tonsillitis, high fever, headache, nausea, vomiting, malaise; occurs 1 to 3 days after eating, lasting a few days to about a week.

Listeria monocytogenes
Found: intestinal tracts of humans and animals, milk, soil, leaf vegetables, and processed foods; can grow slowly at refrigerator temperatures.
Transmission: soft cheese, raw milk, improperly processed ice cream, raw leafy vegetables, meat, and poultry. Illness caused by bacteria that do not produce toxin.
Symptoms: fever, chills, headache, backache, sometimes abdominal pain and diarrhea; 12 hours to 3 weeks after ingestion; may later develop more serious illness (meningitis or spontaneous abortion in pregnant women); sometimes just fatigue.

Shigella (over 30 types)
Found: human intestinal tract; rarely found in other animals.
Transmission: person-to-person by fecal-oral route; fecal contamination of food and water. Most outbreaks result from food, especially salads, prepared and handled by workers using poor personal hygiene.
Symptoms: disease referred to as “shigellosis” or bacillary dysentery. Diarrhea containing blood and mucus, fever, abdominal cramps, chills, vomiting; 12 to 50 hours from ingestion of bacteria; can last a few days to 2 weeks. Sometimes, no symptoms are seen.

Staphylococcus aureus
Found: on humans (skin, infected cuts, pimples, noses, and throats).
Transmission: people-to-food through improper handling. Multiply rapidly at room temperature to produce a toxin that causes illness.
Symptoms: severe nausea, abdominal cramps, vomiting, and diarrhea occur 1 to 6 hours after eating; recovery within 2 to 3 days—longer if severe dehydration occurs.

Are Raw Fed Pets a Threat?

After learning about all the places bacteria lurk in the environment and the foods that carry potential risks, it is sad that pets often become the brunt of germ phobia. Faithful felines and devoted dogs provide innumerable emotional benefits to their owners and the elderly or handicapped in nursing and care homes. Unfortunately, therapy pets are often rejected if fed a raw food diet. In short, therapy organizations fear that pathogens in raw food diets will be transmitted from the dog or cat (through saliva and contact with the pet's fur) to humans with weakened immune systems, resulting in life-threatening illness.

However, salmonella outbreaks in hospitals, institutions for children and nursing homes are not uncommon and usually arise from food contaminated at its source, or less often, during handling by an ill person or a carrier. The common occurrence and dire consequences of infectious disease outbreaks in nursing homes often go unrecognized. Regardless of whether a therapy pet is fed a raw diet or not, nursing and care homes are an ideal environment for acquisition and spread of infection: susceptible residents who share sources of air, food, water, and health care in a crowded institutional setting. Moreover, visitors, staff, and residents constantly come and go, bringing in pathogens from both the hospital and the community.

Studies of pet dogs show that food-borne pathogens are present in a surprisingly large proportion of dogs tested. Hackett and Lappin (2003) found infectious agents in the faeces of 26% of healthy Colorado dogs Fukata et al (2002) found salmonella antibodies in 15% of apparently healthy dogs. (Not limited to dogs eating raw diets.)

The chance of Felix or Fido passing on a nasty bug may increase if a person's immune system does not function optimally but some experts believe the benefits of animal companionship far outweigh any hazards. In the face of bacteria hysteria, it's worth remembering that bacteria are everywhere, and we've been happily co-existing with them for millennia.

Kibble Risks

It is interesting that veterinarians are concerned about the safety of raw food diets, yet ethics get shoved under the carpet when it comes to health problems associated with kibble and canned pet foods and treats. Improperly handled raw pet food is no more dangerous than improperly handled kibble or canned pet foods.
Dry dog and cat food can look surprisingly tasty to a toddler. Since they can be choking hazards, it's essential to keep pet food locked away. But this fact is never mentioned on a bag of dry pet food! Responsible instructions might include the following message to consumers:

  • place feeding bowls and dispensers out of the reach of babies and small children
  • remain in the area while you pet finishes a meal
  • dispose of any uneaten food promptly
  • free-choice feeding presents a choking hazard to babies and small children.
  • Kids aren’t the only ones at risk.

Dogs that gulp their food can choke on dry kibble. Dry food can be soaked, but then it cannot be left out. One pet food manufacturer recommends moistening dry puppy food with water to release more aroma, improve palatability and make it easier for puppies to chew. However, bacteria in moistened dry pet food multiply rapidly. How many pet owners plop canned food into a pet dish and leave it there for the day? How many people have toddlers that could potentially come across this food or the dirty bowl?

Today it seems that everywhere we turn, there is another product to eradicate bacteria, but that may not necessarily be a good thing. If there is no exposure to bacteria, immune systems won't build the antibodies they need to stay healthy. Humans and dogs have both good and bad bacteria in their bodies. When we are healthy, there is a balanced level of each. For instance, at any given time, we have traces of E.coli or Salmonella strains running through our systems, along with good bacteria. The body has an amazing health-regulating ability that combats a diverse amount of environmental factors. As bad bacteria are introduced, the immune system fights back with its own army of bacteria.

In carnivores, the colon is short and simple because meat can go off quickly and produce toxins. The longer such food stays inside the body, the more toxins are produced. Therefore, the meat eater's intestine is designed to take out this waste as quickly as possible so the risk is negligible under normal conditions.

If you are considering a raw diet for your dog but you are worried about bacteria for yourself or your family, ensure that foods are purchased from reliable sources and that they are handled correctly from the time you purchase them to the time they are fed. Make certain raw pet food products are kept frozen until thawing prior to feeding. Proper handling at home is an important key. Good hygiene, especially washing your hands often and for at least one minute, is the most effective way to control the spread of bacteria. Keep countertops and cutting boards sanitized and wash your dog's bowl after feeding. Pick up your dog's feces immediately following defecation and dispose of them appropriately.

A Word about Antibacterial Agents

We must understand that bacteria are necessary to life and by using antibacterial agents we are helping to create super-bacteria that will be immune to the strongest antibiotics. Antibacterial agents are now added to dishwashing and laundry detergents, and hand soaps. Products containing antibacterial agents are currently a big marketing ploy used by companies trying to find a new reason for you to buy their products. Research has discovered that E.coli can develop resistance to Triclosan, one of the common antibacterial ingredients in antibacterial soaps. Triclosan works by acting on a single gene to kill the bacteria. Creams and ointments are also loaded with antibacterial agents so even these should be used cautiously as bacteria may develop resistance.


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The information on this website is not intended to replace Veterinary medical advice.