Year of grant:
Náttúra og náttúrutilfeingi
Virulentur ILA virus aftur ávístur í Føroyum.
Debes Hammershaimb Christiansen
Dr. Knut Falk, Dr. Maria Aamelfot, Dr. Iveta Matejusova og Dr. Alistair J. A. McBeath
Grant from the FRC in DKK:
Atlantic salmon aquaculture is one of the most important industries in the Faroe Islands and has increased from the beginning in the 1970s to a production of approximately 86.000 tons of a value of more than DKK 2500 million in 2014. Infectious salmon anaemia (ISA) disease epidemics have raged most major Atlantic salmon producing countries and resulted in an almost total collapse of the Faroese farming industry ten years ago. Lack of national management strategies on the prevention and control of ISA played a major role in the devastating consequences of the ISA epidemics. Based on current knowledge on ISA most countries have implemented national management strategies. However knowledge on ISA virus (ISAV) functional characteristics, aetiology, epidemiology and pathogenesis is incomplete including the association between non virulent and virulent ISAV variants (Håstein et al. 1999).
We and others have shown that a non-virulent ISAV, designated ISAV-HPR0 (Mjaaland et al., 2002), is highly prevalent and only causes a transient and non-clinical infection localized to the gills in farmed Atlantic salmon (Christiansen et al. 2011, Lyngstad et al. 2012). It has been hypothesized that new virulent variants of ISAV have arisen in aquaculture through known and unknown genetic changes in ISAV-HPR0. Although central in the development of ISA disease, the factors driving the ISAV-HPR0 evolutionary dynamics as well as the putative functional differences between ISAV-HPR0 and virulent ISAV, is virtually non-existent.
Last year a new virulent ISAV variant re-emerged at a Faroese marine farming site. Preliminary studies have demonstrated that the isolate is of relatively low-virulence. Furthermore the Atlantic salmon originated from a freshwater pre-smolt farm which was tested ISAV-HPR0 positive. Thus the epidemiologically linked material provides us with a unique opportunity to clarify if the ISAV-HPRO at the pre-smolt farm is the ancestor to the re-emerged virulent ISAV strain at the marine site and which mutations are required for the transition of non-virulent to virulent ISAV variants.
The present project suggests to (I) perform whole genome sequencing of the re-emerged virulent ISAV and associated fresh-water ISAV-HPR0 variants to elucidate the link between non-virulent and virulent ISAV, (II) perform a longitudinal infection challenge of pre-smolt to study the evolutionary dynamics of this low-virulent ISAV variant. In the very fast growing farming industry on the Faroe Islands updated risk assessment of new ISA outbreaks including knowledge on ISAV biology is highly demanded by the authorities and the farming industry.