Practical application of risk assessment in the control of infectious salmon anaemia in Scotland

Infectious salmon anaemia (ISA) is a List I viral disease under the fish disease control regulations of the European Union and immediate containment and eradication of any outbreaks of this disease are required in any Member States. The detection of ISA in a salmon farm on the West of Scotland in 1998, and its subsequent occurrence on several other farms, initiated enforcement of the control measures specified in these regulations. Information providing evidence or suspicion of the presence of the disease led to restrictions on the affected farms to ensure the containment of infection. Similar restrictions were initiated during the killing and disposal or processing of the affected stocks and for the disinfection of equipment. While considerable emphasis was placed initially on previous experiences with the disease in other areas, national, local and even site-specific assessments had to be made within Scotland as new research and field information became available. Risks arising from the possible sources of infection, the mechanisms of disease spread and the eradication methods which could be applied were continually re-assessed to develop locally relevant practices fort he detection, diagnosis, prevention of transmission and neutralisation of the infection. A dynamic and highly responsive risk assessment process was required, together with an awareness of how this experience may impact on current fish disease control regulations.