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Diseases of Aquatic Organisms

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DAO 61:179-185 (2004)  -  doi:10.3354/dao061179

Experimental induction of gill disease in Atlantic salmon Salmo salar smolts withTenacibaculum maritimum

Mark Powell1,*, Jeremy Carson2, Rebecca van Gelderen1

1School of Aquaculture, Tasmanian Aquaculture and Fisheries Institute, University of Tasmania,Locked Bag 1370 Launceston, Tasmania 7250, Australia
2Fish Health Unit, Tasmanian Aquaculture and Fisheries Institute, Department of Primary Industries,Water and Environment, PO Box 46, Kings Meadows, Tasmania 7249, Australia

ABSTRACT: An experimentally induced bacterial infection of marine Atlantic salmon Salmo salar smolt gills was developed using strains of Tenacibaculum maritimum originally isolated from disease outbreaks in Tasmania. The gills of salmon were inoculated with a high concentration of bacteria (4 × 1011 cells per fish) of either strain 00/3280 or 89/4747 T. maritimum. Gentle abrasion of the gills was used to enhance the progression of gill disease. One strain (00/3280) was highly pathogenic, causing morbidity and mortality within 24 h post-inoculation, and produced acute focal branchial necrosis associated with significant increases in plasma osmolality and lactate concentration compared with controls (non-inoculated) or strain 89/4747-inoculated fish. There were no differences in the whole body net ammonium flux between control (non-inoculated) and strain 00/3820-inoculated fish. Gill abrasion resulted in acute telangiectasis and focal lamellar hyperplasia in all fish regardless of bacterial inoculation. This work provides the basis of a challenge model suitable for investigating the pathophysiological processes associated with acute branchial necrosis in marine fish, suggesting that osmoregulatory and possibly respiratory dysfunction are the primary consequences of infection.

KEY WORDS: Atlantic salmon · Tenacibaculum maritimum · Pathophysiology · Gill disease · Osmoregulation · Respiration

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