A comprehensive review published in 2021 in Topics in Companion Animal Medicine has shed new light on the complex microbial communities that inhabit various parts of dogs’ bodies. The study, conducted by Ana Margarida Pereira from the University of the Azores and Alfonso Clemente from the Spanish National Research Council, provides a detailed overview of the canine microbiome from “tip to toe”.
Recent advancements in high-throughput sequencing techniques have allowed researchers to gain unprecedented insights into the microbial communities living in symbiosis with dogs. These communities, collectively known as the microbiome, play crucial roles in canine health and disease.
The researchers found that different body sites in dogs harbour distinct microbial communities. For instance, the skin microbiome is dominated by bacteria from the phyla Proteobacteria, Actinobacteria, Bacteroidetes, and Firmicutes, with variations depending on the specific skin region. The ear canal, another important site, is primarily colonised by Proteobacteria, Actinobacteria, Firmicutes, and Bacteroidetes.
Interestingly, the study revealed that the conjunctiva of the eye, previously thought to be poorly colonised, actually hosts a diverse microbial community. The dominant phyla in this location are Proteobacteria, Bacteroidetes, Firmicutes, and Actinobacteria.
The respiratory tract also showed distinct microbial profiles in its upper and lower regions. The nasal cavity is dominated by Proteobacteria, Bacteroidetes, and Firmicutes, while the lower respiratory tract exhibits an even higher abundance of Proteobacteria.
Perhaps the most extensively studied area is the gastrointestinal tract. The researchers noted that the gut microbiome varies along its length, with different bacterial compositions in the small intestine compared to the large intestine and faeces. Firmicutes, Bacteroidetes, Proteobacteria, Actinobacteria, and Fusobacteria are the most abundant phyla in the canine gut.
The review also highlighted the influence of various factors on the canine microbiome. Age, for example, plays a significant role, with puppies showing different microbial profiles compared to adult dogs. Diet was identified as another crucial factor, with different types of food leading to distinct shifts in gut microbial communities.
Importantly, the study emphasised the link between microbiome alterations and various health conditions in dogs. For instance, changes in the skin microbiome have been associated with atopic dermatitis, while alterations in the gut microbiome have been linked to inflammatory bowel disease and other gastrointestinal disorders.
The researchers also discussed the potential of manipulating the microbiome for therapeutic purposes. Probiotics, prebiotics, and synbiotics were highlighted as promising approaches for modulating the gut microbiome to improve canine health.
One of the most intriguing aspects of the review was the exploration of potential interactions between different microbial communities within a dog’s body. For example, the authors noted similarities between the nasal and ocular microbiomes, likely due to the connection via the nasolacrimal duct.
The study also touched upon the concept of the gut-brain axis in dogs, suggesting that the gut microbiome may influence behaviour and stress responses, although more research is needed in this area.
Looking to the future, the authors emphasised the need for further research to fully understand the functional implications of microbiome variations and to develop targeted interventions. They also highlighted the importance of standardising research methodologies to allow for more accurate comparisons between studies.
This comprehensive review provides a valuable resource for veterinarians, researchers, and anyone interested in canine health. By compiling current knowledge on the dog microbiome across various body sites, it lays the groundwork for future investigations and potential microbiome-based therapies in veterinary medicine.
As our understanding of the canine microbiome continues to grow, it promises to revolutionise our approach to dog health, potentially leading to more personalised and effective treatments for a range of conditions.