Description

Infectious salmon anaemia (ISA) is a virus that was first reported in Norway in 1984. The first outbreak in the UK occurred in 1998/9 that was successfully contained. There now have been two further outbreaks of this disease in salmon farms Scotland in 2009. Although the virus has been detected in wild fish the disease has only been reported in farmed fish. In farmed fish the majority of cases occur in seawater.

Signs of Infection

In clinical cases severe anaemia, ascites (accumulation of fluid in the body cavity), haemorrhage in internal organs and darkening of the liver.

Pathways

ISA is most often transmitted by contact with infected live salmon or infected biological materials such as animal wastes or discharges from normal culture operations, slaughter facilities and contaminated equipment including well boats. The virus can spread from fish to fish as infected individual shed viral particles from its blood, gut contents, urine, and epidermal mucus. Fish that survive may become carriers and can continue to shed the virus for more than one month after recovery.