The gut microbiome of Australian cats and dogs: Dietary influences, health impacts, and emerging research

The gut microbiome plays a pivotal role in the health, metabolism, and behaviour of companion animals, yet comprehensive syntheses of its composition and functional relevance in cats and dogs in Australia are overlooked and remain limited globally. This review synthesises current knowledge on the gut microbial communities inhabiting the gastrointestinal tracts of dog and cats, with a particular focus on taxonomic diversity, dietary modulation, and associations with disease states within Australian context. Core phyla including Firmicutes, Bacteroidetes, Proteobacteria, and Actinobacteria dominate the canine and feline gut, but marked interspecies and individual variability is shaped by factors such as feeding practices, living environment, obesity, and chronic disease. Recent studies have elucidated functional signatures linked to conditions ranging from the influence of microplastics to pet gut health, as well as gut-microbiome transmission between pets and their owners, highlighting this area as a promising field of investigation. In parallel, this review contextualizes the broader landscape of pet ownership in Australia, where nearly 70 % of households own pets, and significant resources are devoted to nutrition, veterinary care, and preventive health. Emerging evidence also suggests bidirectional influences between pets and their human companions' microbiota, highlighting opportunities for integrated approaches. We identify critical knowledge gaps, including the need for region-specific microbial baselines, standardized methodologies, and controlled intervention trials targeting microbiome modulation and transmission. By consolidating advances across microbial ecology, veterinary medicine, and translational research, this review provides a foundation for future studies that aim to harness the diagnostic and therapeutic potential of the pet microbiome, thereby improving health outcomes for animals and humans alike.