Infectious salmon anemia (ISA) is the only disease that has caused a complete or partial shutdown of several national salmon farming industries. Thus, EU lists ISA, and WOAH/OIE has listed the HPR0 variant of the ISAV. Failure to control ISA may hinder export of salmon products and further expansion of the aquaculture salmon industry. The animal health legislation in EU is changing, and this may require a control program that will reduce annual detection of ISAV to less than 1% in an active salmon farm location at any time-point. This measure will require, improve surveillance, with focus on biosecurity as well as understanding the changing ISAV virulence in hatcheries and in seawater farms.
This study will support the control of ISA, by allowing for rapid evaluation of the rapid changing virulence of ISAV in hatchery and seawater salmon farms. To achieve this, we will chose ISAV field isolates, which were collected from different ISA field outbreaks representing historical isolates. We will perform transmission studies in salmon with these isolates, and document possible differences in virulence, mortality and pathology in fish. The full-genome of virus from each of these transmission study will be sequenced, and data obtained will be used to pinpoint potential virulence markers. The establishment of ISAV transmission study is important for understanding of infectivity and virulence in salmon. The samples for histology and histopathology will be analysed in collaboration with digital/molecular pathology where these sampels will also contribute for method development. Also, cells-specific transcriptional responses to low- and high-virulent viruses will be compared, supported by ongoing activities in the RCN-financed project EndoVir.
