DAO 44:171-178 (2001)  -  doi:10.3354/dao044171

Identification of infectious salmon anaemia virus in Atlantic salmon from Nova Scotia (Canada): evidence for functional strain differences

Rachael J. Ritchie1, Marcia Cook1, Krista Melville1, Nathalie Simard1, Roland Cusack2, Steve Griffiths1,*

1Research and Productivity Council, 921 College Hill Rd., Fredericton, New Brunswick E3B 6Z9, Canada
2Nova Scotia Department of Fisheries and Aquaculture, Box 550, NSAC Mail Room, Cumming Hall, Truro, Nova Scotia B2N 5E3, Canada
*Corresponding author. E-mail:

ABSTRACT: Infectious salmon anaemia (ISA) is a serious disease responsible for high morbidity in farmed Atlantic salmon Salmo salar in Norway, Scotland and New Brunswick, Canada. Recent attempts to identify different strains of ISA virus (ISAV) based on nucleotide sequence variation have shown that the Norwegian and Scottish samples are similar to one another but markedly different from New Brunswick samples. These data may suggest the presence of different strains on each side of the Atlantic but no functional difference has been found with either strain. We describe the first identification and characterisation of ISAV in Atlantic salmon from Nova Scotia, Canada. Further, salmon infected with the Nova Scotia ISAV do not show typical ISAV pathology or mortality. Sequencing of this new strain showed it to possess greater similarity to ISAV from Norway and Scotland than to ISAV from New Brunswick. These findings are discussed in terms of a possible origin of the Nova Scotia ISAV strain and the existence of an avirulent ISAV strain. The impact of current strain variation studies on our knowledge of ISAV is also discussed.


KEY WORDS: ISAV · Strain variation · Genome characterisation


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