Probability of freedom from salmonid alphavirus (SAV) in the Atlantic salmon (Salmo salar L.) and rainbow trout (Oncorhynchus mykiss) populations of north-western and northern Norway

A stochastic scenario tree was developed in order to estimate the probability of freedom of salmonid alphavirus (SAV) in the Atlantic salmon (Salmo salar L.) and rainbow trout populations of north-western and northern Norway for the year 2007. The model was based on the samples submitted to the National Veterinary Institute (NVI) diagnostic services following disease suspicion. The results indicate that given only one infected site within the region with less than 1% infected fish, there was a 99% probability that the non-endemic region was free from SAV infection in 2007. These results are in accordance with previous study findings for the same year for this region. The used methodology provides an efficient modeling method for the evaluation of the sensitivity of existing, as well as planned, surveillance/monitoring activities in aquaculture.