Small Animal Review: April 2021

In this review paper by Pilla and Suchodolski (2019), the authors summarise the current understanding of the intestinal microbiome in the dog, describing its role in regulating metabolism, protecting against pathogens and educating the immune system, thereby affecting most physiological functions of the dog. In the healthy dog, molecular methods have allowed the identification of non-culturable bacteria in the gastrointestinal (GI) tract. Estimates of the total microbial load now range between 10¹² and 10¹⁴ colony forming units. The gut microbiome in the dog has been found to be relatively stable over a 2-week period, though longer-term variability has not been studied. Along the GI tract, bacterial sequences typically belong to one of five phyla: Firmicutes, Fusobacteria, Bacteroidetes, Proteobacteria, and Actinobacteria.

This paper reports how age, diet and environmental factors may play a significant role in maintaining a healthy microbiome. However, the alterations these factors cause are thought to be much less than the alterations found in diseased animals. GI dysfunctions are commonly associated with a disrupted microbiome. Intestinal inflammation, whether acute or chronic, is associated with significant differences in the composition of the intestinal microbiota. Obesity, metabolic diseases, cancer and neurological disorders are also associated with dysbiosis, although cause and effect are unknown.