Phage Therapy in Aquaculture: Mechanisms, Applications and Future Directions

The aquaculture sector faces increasing challenges from bacterial diseases and growing restrictions on antibiotic use due to concerns regarding antimicrobial resistance (AMR). Phage therapy, the therapeutic application of bacteriophages to selectively infect and lyse pathogenic bacteria, offers a targeted strategy to combat AMR pathogens while minimizing ecological disruption. This review synthesizes current evidence on major bacterial pathogens in aquaculture, with particular emphasis on infections caused by Aeromonas, Vibrio, Edwardsiella, Flavobacterium and Streptococcus species. Available in vivo studies indicate that phage-based interventions, particularly phage cocktails, can significantly improve survival rates in aquaculture species, including catfish, salmonids, and shrimp. However, the current evidence base is dominated by laboratory challenge studies, and substantial heterogeneity in experimental designs, outcome measures, dosing strategies, and host-pathogen systems limits direct cross-study comparisons and broader translational interpretation. Additional challenges include large-scale field implementation, the emergence of phage-resistant bacterial variants, formulation and delivery constraints, and the absence of standardized regulatory frameworks. This review critically evaluates the translational readiness of phage therapy in aquaculture, examines advances in phage isolation, formulation and delivery strategies, and discusses key practical, regulatory and scientific barriers to commercial adoption. Finally, it identifies priority research areas and strategic investments required to facilitate the transition of phage therapy from experimental proof-of-concept to routine practice.