Phage diversity in One Health.

One Health aims to bring together human, animal, and environmental research to achieve optimal health for all. Bacteriophages (phages) are viruses that kill bacteria and their utilisation as biocontrol agents in the environment and as therapeutics for animal and human medicine will aid in the achievement of One Health objectives. Here, we assess the diversity of phages used in One Health in the last 5 years and place them in the context of global phage diversity. Our review shows that 98% of phages applied in One Health belong to the class Caudoviricetes, compared to 85% of sequenced phages belonging to this class. Only three RNA phages from the realm Riboviria have been used in environmental biocontrol and human therapy to date. This emphasises the lack in diversity of phages used commercially and for phage therapy, which may be due to biases in the methods used to both isolate phages and select them for applications. The future of phages as biocontrol agents and therapeutics will depend on the ability to isolate genetically novel dsDNA phages, as well as in improving efforts to isolate ssDNA and RNA phages, as their potential is currently undervalued. Phages have the potential to reduce the burden of antimicrobial resistance, however, we are underutilising the vast diversity of phages present in nature. More research into phage genomics and alternative culture methods is required to fully understand the complex relationships between phages, their hosts, and other organisms in the environment to achieve optimal health for all.