What is Dysbiosis?

A balanced gut microbiota heavily contributes to the normal physiological functioning of the host through protection against potential pathogens, encouraging immune system tolerance and normal metabolism.[1] Dysbiosis can simply be defined as qualitative and quantitative changes to the composition of the microbiota when compared to a group of healthy individuals. This state of dysbiosis can be harmful to the host through alterations in bacterial metabolism and the overgrowth of potentially pathogenic microorganisms. It is thought that the growth of these bacteria in the gastrointestinal tract results in the release of possible toxins that play a role in many chronic diseases.[2]

Studies have demonstrated that diet, lifestyle, stress and antibiotics amongst many other factors can contribute to dysbiosis. The main symptoms often associated with dysbiosis are diarrhoea, vomiting, depression, weight loss and lethargy. However, dysbiosis has been linked to more serious long-term diseases, not only confined to the gut, but also those affecting other body systems.

Measurement and Quantification of Gut Dysbiosis

Gut dysbiosis can be measured and quantified through a PCR-based algorithm called the “Dysbiosis Index”. This mathematical model uses the quantification of total bacteria and a panel of several common bacterial groups to calculate the Dysbiosis Index (DI). Negative DI values indicate normobiosis, and positive DI values indicate dysbiosis. The DI allows us to monitor changes to dysbiosis over the course of a disease or in response to treatments. [1]Studies have demonstrated that DI is increased in dogs with chronic enteropathies.[3],[4],[5]

Dogs with acute diarrhoea and chronic enteropathies such as inflammatory bowel disease (IBD) and haemorrhagic gastroenteritis (HGE) are shown to have a strong dysbiosis with a decrease in short-chain fatty acid producing bacteria, increase in Clostridium genus bacteria and significant decrease in microbial diversity compared to healthy dogs.[6],[7] Similarly, it has been demonstrated that cats with diarrhoea and chronic enteropathies have significant dysbiosis. [8],[9] Whether these changes play a causal role in disease development or occur as an effect of gastrointestinal pathology still requires further research.

Dysbiosis and Non-Gastronintestinal Diseases

Interestingly, dysbiosis has been linked to many non-gastrointestinal diseases in humans and also in dogs. In humans, dysbiosis is associated with type 1 and type 2 diabetes,[10],[11] Parkinsons disease,[12],[13] mental health including depression, [14],[15],[16] colorectal cancer,[17] obesity, [18] and many other diseases. In dogs, meningoencephalomyelitis of unknown origin (MUO) is linked with dysbiosis. More specifically, there is strong evidence that a high abundance of Prevotellaceae in the gut is associated with reduced risk for developing immune-mediated brain disease.[19] Prevotellaceae in the gut is associated with reduced risk for developing immune-mediated brain disease19. Additionally, dogs with congestive heart failure are shown to have an increased abundance of Proteobacteria due to an increase in Enterobacteriaceae and Escherichia coli.[20] Thus concluding dogs with congestive heart failure are likely to have dysbiosis, with further studies in humans also suggesting this.

Dysbiosis and the gut microbiome have been explored extensively in the medicine field. There have been many studies connecting gut dysbiosis to gastrointestinal diseases such as chronic enteropathies and acute diarrhoea. Recently, studies exploring the gut-brain axis in humans have linked dysbiosis to neurological conditions such as Parkinson’s disease and mental health conditions, such as depression. While other diseases including congestive heart failure, immune-mediated brain disease and diabetes continue to be linked to dysbiosis in dogs and humans. Going forward, it is essential that we utilise the plethora of research on this topic and appreciate the adjunctive role that probiotics and prebiotics can play in assisting with the prevention and therapeutic management of disease.

Author: Benjamin Sofaer BVSc, Veterinary Territory Manager at Protexin Veterinary. Protexin Veterinary is a brand of ADM Protexin Ltd

In Partnership With Protexin Veterinary

References

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