However, a little research on google determined that the study in question (link is PDF format) was not published in a peer-reviewed journal. In fact, the study was submitted to the California State Science Fair by E. Jayne Gustafson. Ms. Gustafson’s methodology looks good, but I cannot vouch for the rigorousness of her technique or statistical analysis.
It probably is not true. I read an article in a veterinary journal several years ago that detailed a study in which bacteria were cultured from the mouths of cats, dogs and humans. The article reported that the mouths of dogs yielded the greatest number of bacterial colonies. Cats were second, and humans third.
Dr. Eric Barchas is a professional traveler who spends his spare time working as a full-time veterinarian; contributing to Dogster and Catster; walking, cooking, camping, and exploring the outdoors; skiing (when conditions permit); and reading Booker-shortlisted novels. In between trips Dr. Barchas lives and works in the San Francisco Bay Area with his wife, Denise, and his canine pal, Buster. His main veterinary interests are emergency and critical care, wellness, pain management and promotion of the human-animal bond. Dr. Barchas has to Dogster and Catster since May 2005.
All animals have bacteria in their mouths. A cat’s mouth probably has no more bacteria than the mouth of any creature that does not brush its teeth. However, cats have unique teeth. Their (inappropriately named) canine teeth, or fangs, are extremely long and sharp. When cats bite people or other cats (they tend to use their claws, rather than their teeth, in altercations with dogs), their canine teeth puncture deep into tissues and introduce bacteria. Because the teeth have small diameters, the seemingly minor wounds heal rapidly.
Takes a Licking
If anyone knows what’s in a dog or cat’s mouth, it’s Floyd Dewhirst, a bacterial geneticist at the Forsyth Institute and professor of oral medicine at Harvard. Dewhirst pioneered the study of the oral microbiome—all the bacteria that live in the mouth—in humans, dogs, and cats.
About 400 to 500 bacterial species are common and abundant in the human mouth, he says. So far, Dewhirst and his colleagues have identified around 400 kinds of oral bacteria in dogs and almost 200 in cats, and Dewhirst expects more will be found with further study.
One of the main reasons we can get infections from our pets, he says, is that our bacterial ecosystems are so different from each other.
“If you look at humans and dogs, we only saw about 15 percent that are the same species,” he says. So, many of a dog’s mouth bacteria are less likely to be kept in check by our immune systems and native bacteria. The oral microbiomes of cats and dogs, on the other hand, overlap by about 50 percent. (Also find out what ancient DNA is showing us about cat domestication.)
“Part of that may be what the bacteria evolved to eat,” Dewhirst says. Human mouths are dominated by streptococcal bacteria, which are good at eating sugars. “Since cats and dogs normally don’t eat too many doughnuts, there’s almost no strep,” he says.
A single lick can deposit untold millions of these unfamiliar bacteria, Dewhirst says, and they’ve been detected on human skin hours later. When studying the skin microbiome of humans, scientists were surprised to find several people with patches of skin covered in dog bacteria.
“So, if you’re licked by a dog, and someone were to take a Q-tip five hours later and rub that spot, they could recover over 50 different species of dog-mouth bacteria,” he says.
More so that dogs, cats can be highly aggressive when the mood strikes them. Theyre hard-wired to use teeth and claws to hunt and defend themselves. While your cat may turn up its nose at the fanciest commercial cat food it nonetheless may take great delight in stalking, pouncing on and devouring small animals that enter its domain. If there are no small animals about, your cat may decide to stalk you or other family members instead.
Most importantly, infants should never be left alone with a cat. Any cat, no matter how seemingly docile and domesticated, can respond aggressively when certain instincts are triggered. Infants can be severely harmed in just a few seconds. A photo of a baby sleeping with a cat may be cute but a follow-up photo of the stiches wont be as attractive.
The wrist or any joint in the hand is usually the worst place to receive a bite. In the study it had a higher risk of hospitalization than wounds over soft tissue. A hand, unfortunately, tends to be where a cat will strike, as the victim tries to pet the animal or offer food.
“The dogs’ teeth are blunter, so they don’t tend to penetrate as deeply and they tend to leave a larger wound after they bite,” said senior author Brian Carlsen, M.D., a Mayo Clinic plastic surgeon and orthopedic hand surgeon. “The cats’ teeth are sharp and they can penetrate very deeply, they can seed bacteria in the joint and tendon sheaths.”
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Who Has A Cleaner Mouth, Dog or Human?
You’ve probably heard the expression “a dog’s mouth is cleaner than a human’s mouth” at least once in your life. Most of us have just accepted this as fact, when we think about it at all, but have you ever wondered if it is actually true?
Comparing a dog’s mouth to a human’s mouth is “like comparing apples and oranges,” according to Colin Harvey, a professor at the University of Pennsylvania’s School of Veterinary Medicine and the executive secretary at the American Veterinary Dental College.
This is because both dog and human mouths are full of microbes. While there is some overlap in the types of bacteria between species, there are also a host of different dental bacteria in your dog’s mouth that you won’t find in yours.
Take the bacterial family known for causing periodontal disease in humans and dogs, Porphyromonas. Researchers discovered that dogs have a type of Porphyromonas called P. gulae, whereas human mouths contain its relative, P. gingivalis. Both bacteria are what most of us would consider “dirty,” and can cause problems for dog and human teeth.
In fact, dogs have more than 600 different types of bacteria in their mouths, which is a similar number to the 615 and counting types of bacteria Harvard researchers have found in human mouths. These bacteria can also be joined by other bacteria that we (humans and dogs) pick up from our environments, adding to the mix.
Perhaps part of the reason the idea that “a dog’s mouth is cleaner than a human’s mouth” came to be so widely believed is that we don’t typically swap diseases with our dogs when we swap saliva. You are not going to get the flu from a dog kiss, but you might get it from kissing a human loved one.
Most of the bacteria in your dog’s mouth are not zoonotic, which means you probably won’t get a disease from a big old doggy kiss. There are exceptions to this. Dogs that are fed a raw diet are at an increased risk of contracting salmonella, which can be spread to humans, and you really don’t want to share kisses with a dog that regularly raids the litter box.
In other words, kissing your dog is less risky than kissing another human, but that does not mean that your dog’s mouth is necessarily cleaner than a human’s — he just has a mostly incompatible set of germs.
While we’re on the subject of dog mouths, there is another folk belief that you’ve probably heard before about dog mouths: dog saliva helps heal wounds.
This gets a little more complicated. Most mammals, humans included, lick their wounds. Historically, ancient cultures even believed that dog saliva had curative powers, and the Greeks and Egyptians both used dog saliva in healing practices and featured dogs in their religious healing rites.
They may have been on to something. The act of licking, alone, offers some benefits to wound healing. The tongue removes dirt and debris from the wound site, which lowers the risk of contamination and infection. Of course, too much licking can lead to self-trauma, as in the case of hot spots, and can actually make things much worse.
As it turns out, there are certain proteins in saliva called histatins that can ward off infection, and further research has revealed that there are other beneficial chemical compounds in saliva that can help protect cuts from bacterial infections. As if that wasn’t enough, there is even more evidence that suggests licked wounds heal twice as fast as unlicked wounds.
Dog saliva is not alone in these properties. Human and other mammal saliva show similar wound-healing activity, which might help explain why we instinctively hold a cut to our mouths and kiss “boo-boos.”
Does this mean that you should have your dog lick your wounds, or that you should lick your own wounds?
Maybe not. Not all of the research about saliva was good. Curative properties aside, saliva has its risks. Take the bacterium Pastuerella, for example. This bacterium is harmless in the mouth, but can lead to serious infections if introduced into an open wound, resulting in sickness, amputation, and even death. And there are plenty of other germs we can pick up from our environments in our mouths that we do not want a wound exposed to. Also, excessive licking of a wound can lead to infection and self-mutilation.
In short, while there is some truth to this folk remedy, you are probably better off treating your wounds and your dog’s wounds with more conventional care to avoid any unnecessary risks. If you have more questions about whether or not you should let your dog lick your wounds, contact your doctor or your veterinarian for professional medical advice.
Both dogs and humans are equally susceptible to dental disease and benefit from good oral hygiene practices to keep their mouths clean and healthy. Regular brushing and dental cleanings help humans and dogs keep harmful bacteria, like the kind that cause periodontal disease, in check and are an important part of a daily routine.
You can begin brushing your dog’s teeth when he is a puppy. This will make it easier down the road when your dog is older and full of firm ideas about what he does and doesn’t like. Training your dog to enjoy tooth brushing is just as important as getting him used to the process. Talk to your veterinarian about ways to make tooth brushing enjoyable, and be sure to use toothpaste designed for dogs and never human toothpastes, which can contain harmful substances such as xylitol.
Your dog’s mouth might not be cleaner than yours, but keeping your dog’s mouth healthy will make you feel better about those sloppy, wet dog kisses.
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