Atlantic salmon (Salmo salar L.) post-smolts challenged two or nine weeks after seawater-transfer show differences in their susceptibility to salmonid alphavirus subtype 3 (SAV3)

• Main Authors: J. Jarungsriapisit, L. Moore, G. Taranger, T. Nilsen, H. Morton, I. Fiksdal, S. Stefansson, P. Fjelldal, Ø. Evensen, S. Patel
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Figshare 2016
• Subjects: Space Science; Medicine; Microbiology; FOS Biological sciences; 59999 Environmental Sciences not elsewhere classified; FOS Earth and related environmental sciences; Ecology; Immunology; FOS Clinical medicine; 69999 Biological Sciences not elsewhere classified; 60506 Virology; Sav’; Atlantic salmon; Salmo salar
• Online Access: https://dx.doi.org/10.6084/m9.figshare.c.3606818.v1; https://figshare.com/collections/Atlantic_salmon_Salmo_salar_L_post-smolts_challenged_two_or_nine_weeks_after_seawater-transfer_show_differences_in_their_susceptibility_to_salmonid_alphavirus_subtype_3_SAV3_/3606818/1

Abstract Background Pancreas disease (PD), caused by salmonid alphavirus (SAV), is an important disease affecting salmonid aquaculture. It has been speculated that Atlantic salmon post-smolts are more prone to infections in the first few weeks following seawater- transfer. After this period of seawater acclimatization, the post-smolts are more robust and better able to resist infection by pathogens. Here we describe how we established a bath immersion (BI) model for SAV subtype 3 (SAV3) in seawater. We also report how this challenge model was used to study the susceptibility of post-smolts to SAV3 infection in two groups of post-smolts two weeks or nine weeks after seawater - transfer. Methods Post-smolts, two weeks (Phase-A) or nine weeks (Phase-B) after seawater- transfer, were infected with SAV3 by BI or intramuscular injection (IM) to evaluate their susceptibility to infection. A RT-qPCR assay targeting the non-structural protein (nsP1) gene was performed to detect SAV3-RNA in blood, heart tissue and electropositive-filtered tank-water. Histopathological changes were examined by light microscope, and the presence of SAV3 antigen in pancreas tissue was confirmed using immuno-histochemistry. Results Virus shedding from the Phase-B fish injected with SAV3 (IM Phase-B) was markedly lower than that from IM Phase-A fish. A lower percentage of viraemia in Phase-B fish compared with Phase-A fish was also observed. Viral RNA in hearts from IM Phase-A fish was higher than in IM Phase-B fish at all sampling points (pâ