Experimental infection of Atlantic salmon, Salmo salar L., with infectious salmon anaemia virus: a histopathological study

Recent reports of the isolation of infectious salmon anaemia virus (ISAV) from Atlantic salmon, Salmo salar L., affected by haemorrhagic kidney syndrome (HKS) suggest that ISAV can cause severe renal haemorrhage and necrosis in addition to well-known pathognomonic hepatocellular necrosis and haemorrhage. The prevalence of ISAV-induced pathognomonic renal HKS lesions and their correlation to pathognomonic hepatic lesions of infectious salmon anaemia (ISA) is not known. The present experimental infection of Atlantic salmon with a Canadian isolate of ISAV found that pathognomonic hepatic ISA lesions were present in 90.6% and pathognomonic renal HKS lesions in 78.1% of fish which died after the experimental challenge. Both pathognomonic hepatic ISA lesions and pathognomonic renal HKS lesions were found together in 65.6% of fish which died after ISAV challenge. The present study clearly demonstrates that ISAV can cause a very high prevalence of both HKS and ISA pathognomonic lesions.