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DAO 54:105-117 (2003)
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Abstract
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Experimental mycobacteriosis in striped bass Morone saxatilis
D. T. Gauthier1,*, M. W. Rhodes1, W. K. Vogelbein1, H. Kator1, C. A. Ottinger2
1Department of Environmental and Aquatic Animal Health, Virginia Institute of Marine Science, College of William and Mary, Gloucester Point, Virginia 23062, USA
2United States Geological Survey, Leetown Science Center, National Fish Health Research Laboratory, Kearneysville, West Virginia 25430, USA
*Email: gauthier@vims.edu
ABSTRACT: Striped bass Morone saxatilis were infected intraperitoneally with approximately 105 Mycobacterium marinum, M. shottsii sp. nov., or M. gordonae. Infected fish were maintained in a flow-through freshwater
system at 18 to 21°C, and were examined histologically and bacteriologically at 2, 4, 6, 8, 17, 26, 36 and 45 wk post-infection (p.i.). M. marinum caused acute peritonitis, followed by extensive granuloma development in the mesenteries, spleen and
anterior kidney. Granulomas in these tissues underwent a temporal progression of distinct morphological stages, culminating in well-circumscribed lesions surrounded by normal or healing tissue. Mycobacteria were cultured in high numbers from splenic
tissue at all times p.i. Standard Ziehl-Neelsen staining, however, did not demonstrate acid-fast rods in most early inflammatory foci and granulomas. Large numbers of acid-fast rods were present in granulomas beginning at 8 wk p.i. Between 26 and 45 wk
p.i., reactivation of disease was observed in some fish, with disintegration of granulomas, renewed inflammation, and elevated splenic bacterial densities approaching 109 colony-forming units g-1. Infection with M. shottsii or
M. gordonae did not produce severe pathology. Mild peritonitis was followed by granuloma formation in the mesenteries, but, with 1 exception, granulomas were not observed in the spleen or anterior kidney. M. shottsii and M. gordonae
both established persistent infections in the spleen, but were present at densities at least 2 orders of magnitude less than M. marinum at all time points observed. Granulomas in the mesenteries of M. shottsii- and M.
gordonae-infected fish resolved over time, and no reactivation of disease was observed.
KEY WORDS: Mycobacteriosis · Striped bass · Morone saxatilis · Mycobacterium marinum · Mycobacterium gordonae · Mycobacterium shottsii · Granuloma
Full text in pdf format
Published in DAO Vol.
54, No. 2
(2003) on March 31
Print ISSN: 0177-5103; Online ISSN: 1616-1580.
Copyright © Inter-Research, Oldendorf/Luhe, 2003
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