The Microbiome and diarrhea
We are only just beginning to understand the intricate system of bacteria that live inside the intestinal tracts of humans and animals. Every individual has a unique population of bacteria that is influenced by genetics, diet, the environment, past illnesses and medications.
The numbers and types of bacteria in the microbiome fluctuate with diarrhea but we can’t always tell if that is a cause of diarrhea or an effect of diarrhea. Laboratory testing can identify and measure how many of which types of bacteria are in there but there is a great deal of variation from pet to pet. Telling abnormal from normal is difficult. The gastroenterology laboratory at Texas A & M’s veterinary school has a test for dysbiosis (disturbance of the microbiome) that can be helpful in some cases. It takes 10-14 days to get results back, so it’s not very helpful in-the-moment, but it’s a useful test for chronic diarrhea in dogs. Antibiotic treatment can make diarrhea better in some pets but worse in others.
Sometimes we can identify the overgrowth of a specific type of disease-causing bacteria, such as Clostridium, but we don’t always know if that’s what is causing the diarrhea or whether the diarrhea came first and led to conditions under which the Clostridium could reproduce better. Antibiotics, like diet trials, are usually part of any diarrhea treatment initially, and we find the best one for the pet by trial and error. Some pets need to continue antibiotics long term in order to keep diarrhea-causing bacteria under control. These are usually very narrow-spectrum antibiotics. Our goal is to kill just enough bacteria to keep the system in balance, without killing off too many “good” bacteria.
Diarrhea can be food-responsive, or improve with a change of diet – but we can’t predict which type of diet change will help an individual pet. Low-fat and low fiber diets, such as I/D, are helpful for certain causes of diarrhea but other times a diet with soluble fiber, which is a pre-biotic and supports the growth of beneficial bacteria, works better. If food allergy is a factor then the pet needs a hypoallergenic diet. We don’t have any tests that will indicate what will likely work best, so we figure it out with trial and error. 45-60% of pets with diarrhea will improve on a new diet but the question is always “Which one?”
The intestines are long tubes with distinct layers of cells that perform different functions. The outside layer is structural, the middle layer holds immune system cells and the inner layer is lined with cells that absorb nutrients from the liquified food passing through. The mucous layer that lines the intestinal walls separates bacteria from the deeper layers of the intestinal lining.
If the lining cells are damaged and cannot produce enough mucous, bacteria are able to attach to the intestinal lining cells and then invade beyond the lining. When this happens, a patient needs antibiotics. If the mucous layer is intact, we probably don’t need to use antibiotics and would do better to give a probiotic instead. To know this requires a colonoscopy with biopsy, however. If we could easily see this or test for it somehow we would be much better able to tailor our treatment to be exactly what the patient needs. As it is now, we are guessing whether to use an antibiotic, a probiotic or both.
Our guesses have consequences. When we treat a pet with antibiotics, whether for diarrhea or for any other infection, it can take weeks or months for the microbiome to recover. Sometimes things never go completely back to normal. In human infants, antibiotic treatment leads to higher risk for obesity, and in adults they can be a trigger for Crohn’s disease. We don’t really know whether we could inadvertently be triggering diseases with antibiotics in pets. It may be happening all the time and we just don’t understand the link yet. We don’t use antibiotics if we don’t need to – but some pets require them.
Hang in there if your pet has diarrhea. It can take some experimentation and testing to figure out what works best for an individual patient. We will do our best to get the problem under control as quickly as we can!
Watch our Youtube video on this topic at https://qrco.de/bcdtIA
Recent studies in humans and laboratory animals have shown that the microbial community inside the gut plays a central role in brain function and development. For example, “germ-free” mice, who are born by c-section and are raised in sterile environments, with no exposure to bacteria and no microbiome, do not have normal
brain development. The ‘gut-brain axis’ represents a multi-directional signaling system that encompasses neurological, immunological, and hormonal pathways. Without these signals, the brain functions differently.
In particular, communication between the brain and the gut is tightly linked with the hypothalamic-pituitary-adrenal axis (HPA), a system that regulates stress hormone release and influences brain development and function. Experimental examination of the microbiome through manipulation of diet, infection, stress, and exercise, suggests direct effects on learning and memory.
Calming Care™ is a probiotic supplement, made by Purina, that has been clinically proven to reduce anxiety in about 2/3 of dogs who consume it. I am starting to think that we should be using probiotics for all dogs with behavioral abnormalities.
We don’t understand right now how a human’s or an animal’s individual, unique microbiome affects the brain and vice versa. We know that the gut-brain axis is important. We also know that we humans do better eating a diet with more fiber and less sugar and other refined carbohydrates, in part because soluble fiber supports the growth of gut bacteria. The same is proving true for pets as well.
For now, until we have a more exact understanding of what, when and how influencing the microbiome can improve health, eating a healthy diet and supplementing with probiotics is our blanket recommendation for everyone.
This is not as simple as it might seem, however. For one thing, you have no way of knowing from a pet food label how much soluble versus insoluble fiber is in the food. Insoluble fiber provides bulk to the stool but does not support healthy microbes as soluble fiber does. All you will see on a label is maximums and minimums of protein, fat and carbohydrate. Both types of fiber are part of the total carbohydrate amount. There are only a few pet food manufacturers that know and provide specific information on fiber content. Chances are good that whatever you are feeding your pets does not have an ideal amount of fiber.
There are two prescription diets we use for microbiome support – Hill’s GI Biome and Royal Canin GI Fiber Response. If your dog or cat has chronic diarrhea, we may recommend one of these.
As far as supplementing good bacteria, another problem is that most probiotics on the market do not contain what is stated on the label. When tested in independent laboratories, only two of about 30 different over-the-counter brands of probiotic supplements had live bacteria in the amounts stated on the label, and zero of 19 brands of dry pet food contained any live bacteria. The two brands of probiotic supplements that passed the testing were FortiFlora, made by Purina, and Proviable.
Purina’s research laboratory has been working on the development of probiotics for years, focused originally on the treatment of diarrhea, which is what FortiFlora is used for. In order to provide enough “colony-forming units” of bacteria to have effects beyond the intestine itself, higher numbers of bacteria are needed than are provided in FortiFlora. For this, we have just a couple of good choices.
Proviable has increased the potency of its products recently, to keep up with newer research findings. A new probiotic called Visbiome is also a high-potency product. VisBiome is identical to another probiotic we have been using for years, a prescription human product called VSL#3. This last one was our go-to probiotic for cat respiratory infections for years. VisBiome/VSL#3 has been shown to be as effective as a combination of prednisone and metronidazole for treating IBD in dogs.
We have been modifying many of our medical protocols over the last few years to minimize our use of antibiotics. The more antibiotics, the less healthy the microbiome, and once damaged it can take months or years for normal intestinal bacteria to recover. This can have lasting effects on many body systems. We are trying to use less metronidazole for diarrhea, and a probiotic is almost always being used as part of our treatment now. Skin infections are another area where we are using more topical treatments, such as sprays and shampoos, and fewer antibiotics. We are shortening the length of treatment for urinary tract infections as well.
In summary, if your dog or cat has any sort of behavioral or anxiety disorder then Calming Care would be a good product to try, especially as it has none of the side effects sometimes seen from prescription medications. We also recommend pet foods that contain whole grains, beet pulp and/or chickory, which are all good sources of soluble fiber. Lastly, we will be minimizing antibiotic use when we can.