Can we get the upper hand on viral diseases in aquaculture of Atlantic salmon?

Abstract

Viral diseases are a major problem in Atlantic salmon aquaculture. The development of more effective viral vaccines is crucial for a sustained control of viral diseases in salmon farming because the present viral vaccines are much less effective than the bacterial vaccines. On the other hand, research and lessons from Norwegian aquaculture suggest that major progress in the control of viral diseases can still be made through classical combat principles. Improved and enforced strategies for avoidance and control of viral pathogens by breaking horizontal transmission have yielded encouraging results both for the infectious salmon anaemia virus (ISAV) and for the pancreas disease virus (PDV). More emphasis should also be placed on the possible vertical transmission of viral pathogens. Interestingly, salmon appears to have a relatively strong innate immunity against viruses as it possesses a very well-developed interferon system. Interferons protect salmon cells very well against the infectious pancreatic necrosis (IPN) and PDV and salmon show high resistance against these viruses in challenge experiments. In contrast, these viruses cause high mortality in salmon farming. This suggests that the avoidance of production conditions that result in the suppression of the immune system is of primary importance for the prevention of IPN and PD in the aquaculture industry. Interferons protect salmon cells against the ISAV less effectively, which confirms that ISA must be combated by avoidance and vaccination. Breeding of virus-resistant salmon shows promising results, especially with respect to IPN. Finally, to effectuate the above combat principles, it is important to educate highly competent aquamedicine personnel within the aquaculture industry. In Norway, this is accomplished through a 5-year integrated MSc programme in Aquamedicine.