Research & Development – Marine Scotland Studying ISA, the international way S
Above: Mr Debes Christiansen (FVA, Faroe Islands) and Dr McBeath processing samples. Below: Dr Maria Aamelfot (NVI, Oslo) preparing to sample fish at the MSS aquarium facility in Aberdeen.
cotland is disease free of infectious salmon anaemia (ISA), which contributes substantially to the high health status within the industry and the prevention of signifi cant fi nancial costs. Understanding how to maintain freedom requires good scientifi c knowledge of the virus, susceptibility of fi sh to disease as
well as wider epidemiology. This underpins regulation as well as industry biosecurity. Since the fi rst occurrence of ISA in Scotland in 1998, researchers from Marine Scotland Science (MSS) in Aberdeen have formed a network with scientists from fellow governmental institutions in Norway and The Faroe Islands, at
the Norwegian Veterinary Institute (NVI), Oslo, and the Food & Vet- erinary Authority (FVA), Tórshavn respectively. The collaboration has pooled resources and brought in EU funding for the long term bene- fi t of Scottish aquaculture. There are several current strands
of research but the primary focus recently has been a bath/immer- sion infection trial set up in 2012 (funded by the EU Network of An- imal Disease Infectiology Research (NADIR) Facilities) studying ISAV strain differences using two viruses of high or low virulence, ie severity. Infectious salmon anaemia (ISA) disease outbreaks are caused by variants of the virus with a deletion in the surface protein (haemagglutinin-esterase) with respect to a putative non-path- ogenic ancestral strain called HPR0. Additionally, there is also considerable variation in disease severity and mortality among the disease-causing variants. The HPR0
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strain is found in all major salmon producing areas world-wide and is typifi ed by being found primarily only in the gills and not causing disease. However, the HPR0 virus is diffi cult to study as it current- ly cannot be propagated in the laboratory. So how do you study a virus that cannot be grown? The cross-institution collabora- tion has shown two strains of ISAV have different infection patterns and replicate at different rates, ultimately leading to variations in severity of infection and mortality (McBeath et al 2014a, J Fish Dis; 2014b, Vet Res). Demonstrating variations between viruses of low and high virulence may provide clues as to why HPR0 behaves so differently. In addition Marine Scotland has utilised complex molecular biological and tissue culture techniques to specifi cally demonstrate that alterations in the virus surface proteins can affect the ability of the virus to enter host cells (Fourrier et al, 2014, J Gen Virol). Together they aim to improve our understanding of ISAV infection mechanisms for the mutual benefi t of our industries that ensure preventive measures are up to date and may enable new approaches to prevention or vaccination. A good example of this is that Marine Scotland’s scientifi c fi ndings have informed recent reg- ulatory changes whereby only the deleted, disease-causing variants are listed and notifi able within the EU. This was in response to the separation of the two forms of the virus by the world animal health organisation (OiE). FF
DR ALASTAIR MCBEATH IS A RESEARCHER IN THE MARINE SCOTLAND SCIENCE AQUACULTURE & FISH HEALTH RESEARCH GROUP WITH OVER 15 YEARS’ EXPERIENCE IN THE MOLECULAR ANALYSIS OF FISH PATHOGENS.
www.fishfarmer-magazine.com
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