Figure 1

Illustration of the experimental setup. 130 Atlantic salmon were vaccinated with AQUAVAC^® PD7 into a 500 L tank with flow through freshwater at 12 °C (PD vacc.). As controls, 130 Atlantic salmon were injected with a sterile saline solution and put in a separate tank with same conditions (Un vacc.). Six weeks post vaccination (wpv ≈ 500 degree-days), intramuscular challenge with a Norwegian SAV isolate was performed. Following challenge, 120 fish from each group were allocated in duplicate tanks holding 60 vaccinated or unvaccinated fish each (tanks 1–4). The remaining 10 fish from each group were mixed in a separate tank (tank 5). Water samples (WS) were collected from tanks 1–4 at day 1, 4, 10, 14, 18 and 24 post challenge. 1 day post challenge (dpc), naïve cohabitants were added to tanks 1–4 (n = 10 per tank). Serum was sampled from the naïve cohabitants 24 dpc. 10 days post challenge, serum and faeces were sampled from all fish in tank 5 (n = 10 per group).