Mycobacterium Marinum: Pathological Features and Occurrence in Clinically Diseased Fishes Reared in Aquaculture: A Systematic Review

Mycobacterium marinum is a slow-growing, non-tuberculous, acid-fast bacterium that causes chronic granulomatous infections in fish and is recognized as a zoonotic risk to humans. This pathogen infects various species of freshwater and marine fish; this systematic review gathers information on the pathological features and prevalence of Mycobacterium marinum infections in fish that exhibit clinical signs from aquaculture systems. We conducted manual searches as well as utilized Web of Science, PubMed Central, and Google Scholar HINARI for electronic bibliographic data. An initial review of 392 articles resulted in the selection of 15 studies for the final analysis. Numerous studies conducted between 2000 and 2023 in Europe, Asia, and the Americas indicated an average prevalence of M. marinum at 57.5%, with a variation from 8.5% to 100%. These studies mainly adopted cross-sectional designs and typically employed diagnostic methods that included a combination of clinical signs, gross/necropsy examinations, histopathology, tissue culture with staining, and molecular detection techniques to isolate and identify M. marinum from tissue samples. The liver, kidney, and spleen were the organs most frequently affected, exhibiting granulomatous lesions, colonies of mycobacteria, and infiltration of mononuclear immune cells. Fewer lesions were detected in the gonads and muscle tissues. Importantly, no research from African aquaculture systems was found. This review underscores a concerning increase in the prevalence of M. marinum over time and stresses the critical necessity for improved biosecurity measures, uniform diagnostic protocols, and localized monitoring approaches to mitigate disease risks in aquaculture.