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May 6, 2020 – The microbiome is a diverse collection of microscopic organisms that share our living space (and our bodies). Once viewed as freeloaders or, worse yet, potential invaders, scientists now know that these organisms play a critical role in maintaining good health. These roles include many jobs our bodies do daily, from helping fend off dangerous pathogens and digesting food, to influencing inflammation in the body and even brain function.

Our dogs have their own microbiome and we are learning more about how their microscopic companions influence health and disease, including:

  • Estimates suggest there are 10 times more organisms in the intestinal tract than total cells in a dog’s body
  • Dogs have several hundred families of bacteria in their intestinal tract, but 99% belong to one of five main groups: Firmicutes, Bacteroides, Fusobacteria, Proteobacteria and Actinobacteria
  • The largest number of gut organisms live in the large intestine
  • The skin and urinary tracts also have robust microbiomes
  • Areas previously thought to be sterile, such as the lower airways and even the blood, may have a small normal microbiome
  • The gut microbiota help digest nutrients the dog’s body couldn’t do without their help

More and more studies suggest that the composition of the gut microbiome can have a profound effect on overall health – and not just in the gastrointestinal tract. Numerous studies in people have demonstrated that many diseases appear to be influenced by microorganisms inhabiting the gut, including autoimmune disease, mental disorders  and cancer, and the list keeps growing. Veterinary scientists are just beginning to look at whether the gut microbiome has similar effects in dogs.

A who’s who of the gut microscopic world

The gut is home to a wide variety of microorganisms. Some of the major players include:

  • Bacteria
  • Viruses
  • Fungi
  • Protozoa
  • Archaea

These denizens of a dog’s intestinal tract tend to live in harmonious balance. However, if one or more types comes to dominate the others, this disruption can trigger health consequences. Dysbiosis is the term that describes this state of imbalance. Dysbiosis often occurs secondary to another problem, but it can self-perpetuate and cause additional problems.

Scientists are just learning how these organisms interact with each other, how they work together to promote the health of the host, and how they restore themselves to balance when disrupted by disease, dietary changes or other external forces.

What does a normal microbiome look like in dogs?

Scientists have long recognized that hundreds of different types of organisms live in the gastrointestinal tract, but because many of the normal inhabitants won’t grow outside of the intestinal tract in petri dishes, the actual composition of the gut was a mystery for decades. Recent advances in technology allowed researchers, for the first time, to take a deep look at these organisms  and what they are learning is surprising.

Researchers were stunned to learn of the complexity of this population, and the number of scientific studies focused on the microbiome exploded. Veterinary scientists jumped on the chance to study the gut microbiome in many different animal species, including in both healthy individuals and in animals suffering from disease.

These descriptive investigations provided much needed inventories of the gut inhabitants and helped shape what constitutes as normal for a specific species, including our dogs, at a particular life stage. This new information is critical to help identify dysbiosis in sick animals; knowing normal from skewed gut microbe balance is the jumping off point for many studies.

Keeping the microbiome happy  - an important component of overall health care?

Dog owners know that caring for their pet includes routine checkups, proper diet, exercise, vaccinations and lots of love. What many pet owners don’t know is that they’ve also become the caretakers of the billions of organisms that live in their dog’s intestinal tract – likely not something they signed up for when they first got their dog!

One thing most veterinary scientists agree on is diet has a major influence on gut bacteria. Fiber supplementation has been well studied as part of the treatment of certain diseases, such as diabetes and colitis. But we’re also learning that fiber is an important nutrient for the bacteria in the gut, too.

Prebiotics are food stuffs that provide nutrients to gut bacteria, and fiber is the prebiotic most familiar to people. The metabolism of fiber generates lots of different substances that keep the microbes and the cells of the intestinal tract in our dogs’ guts happy

Research also shows that high-fiber diets have been associated with greater diversity and number of gut bacteria in people, which in turn are associated with positive health benefits. High-fiber diets also can affect the microbiomes of our pets, although veterinary research lags behind in understanding what is optimal. However, unless a dog has an underlying disease that precludes the use of a high-fiber diets, ask your veterinarian if your dog would benefit from dietary fiber supplementation.

Changes in the gut microbiome – cause or consequence of disease?

It’s probably not a surprise to learn that diseases of the intestinal tract lead to dysbiosis. What is surprising is that other diseases involving systems far away from the gut can be associated with dysbiosis. For many researchers, this has resulted in a chicken/egg question – did the gut microbiome shift, resulting in disease elsewhere, or did a disease in another body system lead to changes in the gut?

The short, and somewhat unsatisfying, answer is that it might be a little of both in some cases.

Evidence shows that many factors can change the microbiome composition, sometimes temporarily and sometimes for long periods of time (or permanently). For example, antibiotics can skew the gut microbiome, which is logical given that these medications are designed to treat bacterial infections. As mentioned earlier, diet also can change the gut microbiome composition.

But other factors that can alter the gut microbiome, such as smoking, sleep, stress, antacids, artificial sweeteners and exercise, are not as intuitive. These factors can alter the microbiome in people and there’s growing evidence they can affect our dogs, too.

Decreasing a dog’s exposure as much as possible to second-hand smoke, certain types of people food, as well as ensuring they get adequate exercise and rest might be important factors in not only keeping dogs healthy but keeping their microscopic friends happy, too!

Fecal microbiota transplantation – not as weird as it sounds

Fecal microbiota transplantation (FMT) is the process of transferring fecal material from one individual to another. Although it sounds a little gross, FMT is becoming increasingly accepted in human medicine. The transfer usually is administered by enema, although capsules filled with purified and dried organisms also are used.

FMT has transformed the treatment of recurrent C. difficile infections in people and is now under investigation as a potential treatment for a lot of diseases in people.

Veterinarians also are using FMT to treat a variety of conditions both in and outside the gut. One example is a recent study where fecal transplantation was used in client-owned puppies with parvovirus infection.  All puppies received standard care, with half of the affected puppies also given fecal microbiota transplantations. Although mortality was equal in the two groups, the surviving puppies receiving FMT had faster resolution of diarrhea and shorter hospitalization than the surviving control puppies. Also, the addition of the FMT significantly decreased treatment costs.

Using FMT for other diseases is a very active area of research in veterinary medicine and might provide another method of changing the gut microbiota to a more favorable configuration as well as providing a new treatment component for many diseases inside and outside the intestinal tract.

Manipulating the gut microbiome for better health – science fiction or reality?

The final frontier for many researchers is the ability to precisely alter the gut microbiome to improve health or as part of the treatment for a specific disease, such as with fecal microbial transplantation.

Other researchers are looking at using oral probiotic cocktails as a way of altering gut microorganisms, and still others are looking at how diet alterations might change the microbiome. An area of active research, altering the microbiome is an exciting new avenue of therapy for many diseases, including cancer and chronic inflammatory diseases.

Morris Animal Foundation is at the forefront of microbiome research. Our portfolio includes microbiome research in a large number of species, from dogs and cats to horses and wildlife. Learn more about our microbiome research and all we’re doing to advance animal health around the world.