The canine gut microbiome as a translational model for human health and aging.

The domestic dog is increasingly recognized as a complementary translational model for microbiome research relevant to human health while also offering direct benefits for veterinary medicine. Dogs share environments and dietary exposures with humans and show substantial taxonomic and gene-content similarity to the human gut microbiome, although the apparent degree of similarity depends strongly on whether read recruitment, gene-catalog overlap, or functional overlap is assessed. Dogs also develop spontaneous chronic enteropathies, obesity-associated metabolic dysfunction, cancers, cognitive dysfunction, and behavioral disorders in which gut microbial changes can be examined under clinically realistic conditions. Their shorter, breed- and body-size-dependent lifespan permits repeated sampling across development, aging, disease progression, and treatment within practical timeframes. Breed structure, full-sibling cohorts, controlled dietary interventions, and access to clinically indicated samples from multiple anatomical compartments can strengthen selected study designs, although they do not provide the tighter genetic, environmental, and microbial control achievable in rodents. Here, we evaluate the research questions for which canine cohorts are especially informative, synthesize evidence linking canine and human disease-associated microbiomes, and critically assess aging, causal inference, and One Health applications. Major limitations include the need for breed and body-size stratification, heterogeneous diet and husbandry, incomplete treatment histories, the lack of routinely available gnotobiotic canine systems, and gaps in canine-specific reference resources. The canine system is therefore most informative when study designs exploit its clinical realism while acknowledging the tighter experimental control offered by reductionist models, positioning the dog as a complementary rather than a universally superior model.