Abstract
<jats:p>This paper seeks to critically review the occurrence and variety of waterborne pathogens in aquaculture systems and examine their effects on the immunological status of commercially significant aquatic-based organisms through secondary source material. A systematic secondary data analysis was carried out in 86 publications, released in 2020-25, and found in databases (PubMed, Scopus, and Web of Science). The data entailed over 52,000 observations of fish in different geographical locations. The relationships between the pathogen load and immune response were determined using standardized methods to estimate the prevalence of pathogens, Immunological Response Index (IRI), correlation, regression, and meta-analysis. The overall prevalence of the pathogens was 41.3% (12.4% to 68.7%). The most common were bacterial infections (52%), parasitic (31%) infections, and viral (17%) infections. The prevalence was higher in the region of Asia (48.6%) and Africa (44.1%) than in Europe (32.8%) and the Americas (36.5%). The average IRI was 1.12, which represented an average immune response. A strong positive correlation (r = 0.68, p < 0.01) and regression model (R² = 0.46) confirmed that pathogen prevalence significantly influences immune response. The effect size (Cohen’s d = 0.74) was significant due to meta-analysis. The study observes that the abundance of waterborne pathogens has a tremendous effect on the immune health of fish and is influenced by the environment and management. These results highlight the importance of better disease surveillance, early diagnostic biomarkers, and sustainable aquaculture.</jats:p>