Bacterial Diseases in Farmed Nile Tilapia ( Oreochromis niloticus ): A Review of Pathogenesis, Immune Responses and Recent Advances in Diagnostics and Management

ABSTRACT Nile tilapia ( Oreochromis niloticus ) is among the most widely farmed fish globally that plays a major role in ensuring food security in many low‐ and middle‐income countries. This is attributed to its environmental tolerance, ease of breeding, rapid growth, efficient feed use and high consumer acceptance. As aquaculture production intensifies, bacterial diseases increasingly constrain yields and economic benefits. Although many studies document bacterial outbreaks and have evaluated interventions, heterogeneity across pathogens in virulence, geographic distribution, mortality patterns, environmental drivers and antimicrobial resistance (AMR), together with differences in study designs and outcome, limit a unified understanding of disease risk. Following Preferred Reporting Items for Systematic Reviews and Meta‐Analyses (PRISMA) guidelines, we systematically searched PubMed, Web of Science and Scopus; of 689 records identified, 615 remained after removing duplicates, and 399 full texts were assessed after removing 216 articles that were not clearly relevant to the review topic. Of 399 full‐text articles assessed, 87 articles were excluded, yielding 312 studies that met inclusion criteria for qualitative synthesis. This review synthesizes evidence on major bacterial pathogens, epidemiological and environmental drivers, AMR, virulence mechanisms, host innate and adaptive responses, diagnostics and disease management strategies. Streptococcus , Aeromonas , Francisella and Edwardsiella emerged as major bacterial taxa of global importance, although emerging and opportunistic pathogens can also cause severe disease outbreaks under stressful conditions. Disease outcomes reflect interactions among pathogen virulence, host susceptibility, environmental stress, co‐infections and husbandry practices. AMR is an additional One Health concern through resistance selection, horizontal gene transfer, mobile genetic elements and environmental dissemination into aquaculture systems. Sustainable disease management requires integrated, data‐driven strategies that link pathogen surveillance, biosecurity, environmental stewardship and preventive disease management.