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Mycobacteriosis is a chronic or acute, systemic, granulomatous disease that occurs in aquarium and culture food fish, particularly those reared under intensive conditions. Mycobacteriosis results from infection by several species of Mycobacterium, aerobic, Gram-positive, pleomorphic rods which are members of the order Actinomycetales and family Mycobacteriaceae. Mycobacteria are widespread in the environment, particularly in aquatic reservoirs. The two most important species causing mycobacteriosis in fish and humans are Mycobacterium marinum and Mycobacterium fortuitum. Other species known to cause mycobacterial disease in fish include M. chelonei, M neoaurum, M simiae, and M scrofulaceum.

Mycobacterium marinum was first recognized in 1926 from the liver, spleen and kidney of tropical coral fish kept in the Philadelphia Aquarium. M. marinum can grow prolifically within fibroblast, epithelial cells and macrophages. In the past, human outbreaks of M. marinum were sporadic and most commonly associated with contaminated swimming pools. Chlorination practices used today have greatly minimized to frequency of outbreaks from these sources. In the last decade, a small but steady increase in the frequency of Mycobacterium marinum infections in cultured or hatchery confined fish and human cases associated with fish aquaria has been noted.

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Iowa State University



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