Understanding Microbiome Variability in Healthy Dogs: Implications for Microbiome Testing

Course overview

Advances in canine microbiome research have transformed our understanding of gastrointestinal health, revealing associations between microbial community structure and a wide range of digestive, metabolic, and immune-mediated conditions. As microbiome testing becomes increasingly integrated into veterinary practice, clinicians are often faced with interpreting changes in bacterial abundances and determining whether those changes represent disease, dysbiosis, or normal biological variation. One of the most important unanswered questions in companion animal microbiome science has been the degree to which the microbiome naturally fluctuates over time in healthy individuals. While cross-sectional studies have identified bacterial taxa associated with health and disease, comparatively little attention has been paid to the temporal stability of these organisms or the extent to which healthy microbiomes vary from month to month. This course reviews recent longitudinal research evaluating the fecal microbiomes of 35 healthy dogs sampled monthly over one to two years using full-length 16S rRNA gene sequencing. Participants will explore how microbial communities change over time despite consistent diets, and the absence of antibiotics or medications. Findings demonstrate that temporal variability is an inherent characteristic of the healthy canine gut microbiome and that fluctuations occur both at the community level and among individual bacterial taxa. The session will examine which bacterial species exhibit relatively stable patterns and which taxa are especially dynamic. Particular attention will be given to bacterial groups that commonly generate concern during microbiome testing, including Streptococcus spp., Escherichia coli, and Clostridium perfringens. Beyond reviewing study findings, the course emphasizes practical clinical application. Participants will learn how temporal variability influences microbiome test interpretation, the limitations of single time-point testing, and how healthy reference intervals should be used when evaluating bacterial abundances. The session will also discuss how transient detection of pathogens, toxin genes, or opportunistic organisms should be interpreted in clinically normal dogs. Overall, veterinarians and veterinary technicians will develop strategies for distinguishing normal microbial variation from clinically meaningful dysbiosis.