DAO 97:37-46 (2011)  -  DOI: https://doi.org/10.3354/dao02390

Flavobacterium psychrophilum associated with septicaemia and necrotic myositis in Atlantic salmon Salmo salar: a case report

Hanne Nilsen1,*, Renate Johansen2, Duncan John Colquhoun2, Inge Kaada3, Kirsten Bottolfsen1, Øyvind Vågnes1, Anne Berit Olsen1

1Norwegian Veterinary Institute Bergen, PO Box 1263 Sentrum, 5811 Bergen, Norway
2Norwegian Veterinary Institute Oslo, PO Box 750 Sentrum, 0106 Oslo, Norway
3VestVet A/S, Firdaveien 6, 6800 Førde, Norway

ABSTRACT: We describe the first case from Norway of increased mortality in Atlantic salmon Salmo salar (L.), with septicaemia and necrotic myositis, associated with infection by Flavobacterium psychrophilum. The outbreak occurred in smolt of 60 to 100 g in fresh water on a land-based farm in Western Norway during winter 2008−2009. The water temperature was <5°C and the accumulated mortality was 7.0%. Necropsy of dead and moribund fish revealed a swollen dark spleen, pale liver, serohaemorrhagic ascites and haemorrhage in the abdominal fat and muscle. F. psychrophilum was isolated from the kidney and spleen of diseased fish. Muscle biopsy revealed the presence of long filamentous rods in necrotic areas of skeletal muscle. Immunohistochemistry was positive for F. psychrophilum. Identification of cultured isolates as F. psychro­philum was confirmed using phenotypic testing and sequencing of the 16S rRNA gene. Analysis by allele-specific polymerase chain reaction (allele-specific PCR) indicated that 2 different genotypes of the bacterium were present in the outbreak.


KEY WORDS: Flavobacterium psychrophilum · Atlantic salmon · Necrotic myositis · Septicaemia · 16S rRNA allele


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Cite this article as: Nilsen H, Johansen R, Colquhoun DJ, Kaada I, Bottolfsen K, Vågnes Ø, Olsen AB (2011) Flavobacterium psychrophilum associated with septicaemia and necrotic myositis in Atlantic salmon Salmo salar: a case report. Dis Aquat Org 97:37-46. https://doi.org/10.3354/dao02390

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