DAO 39:97-108 (2000)  -  doi:10.3354/dao039097

Platyspondyly and shortness of vertebral column in farmed Atlantic salmon Salmo salar in Norway-description and interpretation of pathologic changes

A. Kvellestad1,*, S. Høie1, K. Thorud1, B. Tørud2, A. Lyngøy3

1National Veterinary Institute, Box 8156 Dep., 0033 Oslo, Norway
2Veterinary Service in Aquaculture, 6683 Vågland, Norway
3Veterinary Service in Aquaculture, Dragsund, 6080 Gurskøy, Norway

ABSTRACT: Body malformation due to shortness of the vertebral column, in most cases of unknown cause, has been observed in fish for more than 100 yr. It periodically occurs with high prevalence in farmed Atlantic salmon Salmo salar in Norway, and this paper describes the results of macroscopic, radiographic and histologic examination of parr and seawater-transferred fish. The vertebral bodies in both age groups did not acquire the length that they normally should due to a growth disturbance leading to the condition of platyspondyly and shortness in the column. The pathologic changes became visible at different ages in both groups and the process apparently starts in intervertebral tissues. There was proliferation of connective tissue and blood vessels, and sometimes infiltration with inflammatory cells, around affected vertebrae, especially in seawater-transferred fish. This is the first description of inflammation in abnormally short-spined fish, and it may indicate an infectious etiology, at least in farmed seawater-transferred salmon.

KEY WORDS: Norway · Aquaculture · Atlantic salmon · Vertebral column · Disease · Platyspondyly · Sectional shortness

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