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Diseases of Aquatic Organisms

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DAO 52:87-91 (2002)  -  doi:10.3354/dao052087

Mycobacterial infection in farmed turbot Scophthalmus maximus

N. M. S. dos Santos1,2,*, A. do Vale1, M. J. Sousa3, M. T. Silva1

1Institute for Molecular and Cell Biology, Rua do Campo Alegre no. 823, 4150-180 Porto, Portugal 2Novartis Animal Vaccines Ltd, 4 Warner Drive, Springwood Industrial Estate, Braintree, Essex CM7 2YW, United Kingdom 3Instituto Nacional de Saúde Dr. Ricardo Jorge, Laboratório de Tuberculose e Micobactérias, Largo 1º de Dezembro, 4000 Porto, Portugal

ABSTRACT: Mycobacteriosis (piscine tuberculosis) has been reported to affect a wide range of freshwater and marine fish species; however, this is the first report describing mycobacterial infections in turbot Scophthalmus maximus. High numbers of granulomas were initially observed in the organs of moribund farmed turbot. Bacteriological analysis of organs with granulomas led to the isolation of Mycobacterium marinum. Further analysis, to determine the prevalence of the infection in the farm and to identify its source, showed the occurrence of a dual infection by M. marinum and M. chelonae. The presence of Nocardia sp. in some of the fish infected with mycobacteria was also detected. The presence of granulomas in internal organs of apparently healthy fish indicated a high prevalence of the disease, a conclusion that was supported by isolating mycobacteria from all fish with or without granulomas. The infection was probably responsible for the mortality observed (approximately 2% mo-1), as most of the recently dead fish presented high numbers of granulomas and isolation of mycobacteria was possible from all of the fish. The isolation of M. marinum from the inlet water suggested this as the most plausible source for the infection occurring in the farm.

KEY WORDS: Turbot · Scophthalmus maximus · Mycobacteria · Mycobacterium marinum · Mycobacterium chelonae · Nocardia · Granulomas · Fish pathology

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