Bacteriophages (phages) are viruses that infect and may kill bacteria. Phage therapy has gained global attention as a possible means to circumvent problems of bacterial antimicrobial resistance (AMR) in food animal production systems. In preparing this overview on the use of phage therapy in terrestrial food animals, 127 published research articles were analysed to obtain a contemporary background on phage therapy, the efficacy of phage administration, research gaps, and future research directions. Most of the published in vivo trials in chickens described administering phages as biocontrol agents, whereas in vivo trials in pigs administered phages as therapeutics. Only a few trials were conducted in cattle and sheep, targeting foodborne, udder and skin infections. The most common target bacteria in poultry trials were Salmonella Enteritidis, followed by Escherichia coli , Salmonella Typhimurium, Salmonella Pullorum, and Campylobacter jejuni . In contrast, antimicrobial resistant strains of S . Typhimurium and E. coli were the target bacteria in the pig trials. Most studies administered phage cocktails rather than single phage preparation, with bacterial challenge doses varying from 10³ to 10¹⁰ colony forming units (CFU), and phage doses ranging from 10⁵ to 10¹¹ plaque forming units (PFU). In all the reviewed studies phage treatment consistently reduced bacterial load by 0.4 to 5.0 log₁₀ CFU in feces, meat, and both external and internal organs. Moreover, as a therapeutic, phages were reported to cure diarrhea, improve nutrient digestibility, and enhance weight gain. Phage therapy also reduced specific serum IgG levels against the target bacteria and lowered neutrophil counts and TNF-α concentrations. Together these studies suggest that phage therapy may be an effective treatment approach in controlling certain key infections and hence alleviating bacterial resistance in food animals. Nevertheless, global collaboration and inclusive research on cost-effective production, efficient delivery methods, phage resistance, and host immune responses are essential for overcoming hurdles and facilitating the widespread application of phage therapy in food animals. • Most phage efficacy trials in food animals have targeted Escherichia coli , Salmonella spp., Campylobacter jejuni , Staphylococcus aureus , and Clostridium perfringens . • Most studies used polyphage preparations, with challenge bacterial doses varying from 10³ -10¹⁰ colony-forming units (CFU), and phage doses ranging from 10⁵ - 10¹¹ plaque-forming units (PFU). • Phage therapy reduced bacterial numbers by 0.4 - 5.0 log₁₀ CFU in feces, meat, and external and internal organs.
Rahman et al. (Sun,) studied this question.