Wild-Farmed- Viruses in wild and farmed fish in Norway, part 2

-

Samples from 2700 wild fish of 42 different fish species have been collected along the Norwegian coast from Varanger to Stavanger in 2009 - 2011. Part of the material has been tested for VHSV, PMCV and PRV with positive results. The aim of the present stu dy is to investigate the same material for Infectious salmon anemia virus (ISAV) and Salmonid alphavirus (SAV). When it comes to ISAV and SAV the main source of infection has mainly been other farmed fish, and focus on susceptible marine fish has therefor e been scarce. However new knowledge and new problems have lately made marine fish reservoirs more interesting. Low pathogenic strains of ISAV (HPRO) have been detected in high prevalence of both wild and farmed salmonids, and it has been hypothesised t hat these strains may transition into high pathogenic variants of the virus. Several reports conclude that knowledge on possible marine reservoirs for both high and low virulent ISAV is needed. Lately a new variant of SAV (marine SAV-2) have caused majo r problems in Norwegian salmon farming. Different isolates of marine SAV-2 are more heterogenic than SAV-3 and marine reservoirs are therefore more likely. Fish from part 1 of the project will be tested with real time RT-PCR for ISAV / SAV, and any dete ction of virus will be further characterised with both virological and epidemiological methods. We are lucky to have a very good project group with extensive knowledge on many research fields necessary for interpreting any findings of ISAV or SAV in the w ild fish. Any detections of virus will lead to many new questions that need to be addressed in further research. Testing of the already existing material provides a low cost opportunity as a first step into the field of marine reservoirs for ISAV and SAV.