If you’ve ever had a dog, you know all about the tail-wagging, tongue-licking greetings you get in exchange for providing your pooch with food, shelter and ear scratchings.

But in addition to the heart-warming unconditional love, there’s something else that the two of you are sharing—something far less appealing.


Specifically, dental bacteria…the type that can cause cavities and gum disease.

And not only can you catch these germs from your pet, a recent study suggests, but your furry friend can catch them from you, too.

Is this a big deal? Yes. In people, cavities and gum problems can cause tooth loss—and periodontal disease also raises your risk for heart disease, stroke, diabetes, cancer and pneumonia.

And though dogs rarely get cavities, canine gum disease is quite common, affecting 50% to 70% of dogs. In addition to really bad doggie breath and tooth loss, it can lead to bone infections, blood infections and perhaps even organ damage.


For the new study, researchers swabbed the mouths of 66 dogs and 81 human members of their families to look for 10 species of bacteria commonly associated with periodontitis (inflammation and infection of the gums, ligaments and bone that support the teeth) in people, plus one bacterium that is commonly found in dogs but generally not found in humans.

The researchers also categorized the person/pet pairings based on their level of interaction. For instance, low levels of contact occurred when dogs were kept outdoors and seldom saw their owners, or when the person and the pet lived in separate homes…and the highest levels occurred when dogs were kept indoors and had frequent contact with their owners.

Findings: Nine of the 10 species of bacteria commonly associated with human gum disease were also detected among the dogs in the study—and surprisingly, some of these species were even more prevalent in the canines than in the humans. Dogs with high levels of human contact had more species of bacteria than dogs with lower levels of human contact…while dogs that had little or no contact with their human owners did not share any of the same bacteria with their owners.

To see whether the germ swap went both ways, the researchers also looked for evidence of one particular species of bacteria, P. gulae, which is common in dogs but uncommon in humans. Among the study dogs, about 70% had P. gulae, which wasn’t startling. But it was a surprise to learn that 16% of the dog owners also had this bacterium—and all of those owners’ dogs were among the infected. The majority of the people with P. gulae were from the highest-contact category…but the fact that some were in the lower-contact categories suggested that this germ is quite easily transmitted from dogs to humans.

Gum smarts: Now, this study didn’t specifically examine whether people who live with pets actually develop more dental problems than do those in pet-free homes—more study is needed to determine that. (Nor did this study investigate whether kissing a human with gum disease would put you at risk—though that’s an intriguing question which we’ll explore another day.) Still, given the likelihood of pet/person germ swapping, it just makes sense for pet owners to take extra precautions. As a dog lover, I’m not suggesting that we all stop sharing smooches with our pooches. But maybe we can find an alternative that feels equally great—like letting our dogs lick ours ear rather than our cheeks or anywhere else near our mouths. And without question, we can make a point of brushing our teeth well, flossing daily and seeing a dentist at least twice a year…as well as scheduling regular trips to the vet for periodontal checkups for our pets.

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