The Human Microbiome and Man's Best Friend

In the US, approximately 37 to 47 percent of all households have a dog. If you’re one of those dog owners, you might be interested to hear that the dog microbiome can provide additional health benefits beyond what we know from previous research, including enhanced mood and reduced anxiety, stress, and heart disease risk.

Fascinating research has also indicated that man’s best friend may affect the human microbiome in beneficial ways. Some researchers have even offered that a dog may actually act like a probiotic, providing a healthy dose of bacteria to its humans.

How are bacteria transferred from dogs to humans?

Well, one method includes bacteria transferred from a dog’s paws, tongue, and fur to human skin.

One intriguing study regarding the dog microbiome revealed that adults often share many of the same bacteria as their dogs.

This same study also indicated some unexpected results: having a dog may have affect how often bacteria are shared between people residing together.

Couples living together and with at least one dog shared more bacteria than couples without dogs. Why? Researchers found there were additional microbial transfer potentials from one person to the next when a dog lived in the house. For example, one person pets the dog and deposits their bacteria on the fur for the next person that pets the dog.

Even more interesting? Dog owners in general share more microbial species in common with other dog owners compared to dog-less people.

How does the dog microbiome benefit me?

Hygiene hypothesis is a theory centered around the idea that city life and all of modern society’s efforts to avoid pathogens — antibiotics, hand sanitizer, air filters, etc. — have contributed to the increase in allergies and asthma, particularly in children living in urban communities in developed countries.

Scientists believe that living with a dog throughout infancy and childhood may actually reduce the risk of allergies and asthma. Exposure to house-dust related to dogs and other commensal bacteria found in the dog microbiome may be important in helping shape a baby's establishing immune systems.

Another current study, the Human-Animal Interaction Research Initiative (HAIRI), is researching whether a dog directly affects senior health through their bacteria.

Dogs adopted from the local Humane Society were subsequently given to participants over the age of 50 who have either not owned a dog in recent years or previously never owned a dog at all.

The researchers will then monitor both physical and mental health of rescue dog and owner through activity monitors, fecal, mouth, and forehead bacteria samples, blood work, and a series of questionnaires regarding lifestyle, health, and food intake.

Researchers hypothesize that the rescue dogs' beneficial bacteria can be passed on to the owners, similar to probiotics.

The Dog Microbiome Compared to the Human Microbiome: What we Know

- One of the major groups of bacteria that dog owners and their pets share is Betaproteobacteria, which appear on human skin and dog tongues.

- Another major group that can often be found on/in humans and dogs, Actinobacteria, live in soil and often find themselves in the nooks of dogs' paws.

- A dog's gut microbiome is quite simple compared to the human microbiome.

- However, dogs do have complex oral microbiomes, which are quite different from the human oral microbiome. For example, one study found over 350 different types of bacteria in the oral microbiome of 50 dogs. 80% of these species were previously unsequenced.

- Only a small fraction of bacterial species, to be exact 16.4%, found in a dog's intestines were also observed in humans.

So, since they may provide probiotics, you should probably give your dog a few extra cuddles daily. They’ll love it—and so will your health!

References

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Fikes, B. Dog germs may be good for you. The San Diego Union-Tribune. 2015. http://www.sandiegouniontribune.com/news/2015/mar/17/dog-germs-probiotics/

Fujimura, K.W., Demoor, T., Rauch, M. et al. House dust exposure mediates gut microbiome Lactobacillus enrichment and airway immune defense against allergens and virus infection. Proceedings of the National Academy of Sciences of the United States of America. 2013. 111(2). 805-10. doi: 10.1073/pnas.1310750111

Havstad, S., Ganesa Wegienka, Edward M Zoratti, et al.  Effect of Prenatal Indoor Pet Exposure on the Trajectory of Total IgE Levels in Early Childhood. The Journal of Allergy and Clinical Immunology. 2011:  128(4). Elsevier Ltd: 880–885.e4. doi: 10.1016/j.jaci.2011.06.039.

Leach, J. Swapping microbes with your dog. Human Food Project. 2013. http://humanfoodproject.com/swapping-microbes-with-your-dog/

Pet Statistics. ASPCA. 2016. http://www.aspca.org/animal-homelessness/shelter-intake-and-surrender/pet-statistics

Se Jin, S., Lauber, C., Costello, E.K. et al. Cohabitating family members share microbiota with one another and with their dogs. eLife 2013; 2: e0045. doi: http://dx.doi.org/10.7554/eLife.00458

Tse, I. 7 Surprising Health Benefits of Dog Ownership. LiveScience. 2012. http://www.livescience.com/35463-seven-surprising-health-benefits-dog-ownership-110209.html

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