The main objective through this multidisciplinary approach will be to obtain new information that can aid in forming the necessary basis for evaluating important issues related to HPR0, like the risk of infection and its frequency of transition to virulence.

Infectious salmon anaemia (ISA) is still a significant problem for the aquaculture industry in Norway due to direct losses of Atlantic salmon caused by disease outbreaks and the measures taken to control the infection. The severity of the disease is emphasized by the large ISA epidemics unfolding over the past two years within a small geographical region in the county of Troms, having great impact on local economy.

In this project we will be investigating molecular-, functional-, pathologicaland evolutionary properties associated with low- or avirulent ISA virus (ISAV) HPR0 genotypes, assumed to be precursors of all virulent ISAV strains that cause classical ISA outbreaks. The main objective through this multidisciplinary approach will be to obtain new information that can aid in forming the necessary basis for evaluating important issues related to HPR0, like the risk of infection and its frequency of transition to virulence.

Both the authorities and industry request more information concerning this issue in order to be able to take appropriate protective measures, especially as recent findings have shown there is a higher HPR0 prevalence in the marine environment than previously assumed, thus causing interpretation problems related to ISAV screening. The investigations will span both genetic and functional aspects related to HPR0, focusing on determining factors that are required for virulence acquisition. Modified existing methodology, but also powerful new technological approaches, will be used to reach our objective.

The project group has a large and increasing number of HPR0 positive samples at their disposal, both from Norway and the Faeroe Islands, providing a solid foundation for these studies. The results from the project will increase our knowledge on ISAV genetic markers involved in virulence, and may provide a new basis for the development of genetically engineered vaccines against ISA.

Research partners:

• Marine Lab Scotland
• Food, Veterinary and Environmental Agency, Færøyene
• Norges veterinærhøgskole
• Novartis