Non-MHC genetic and tank effects influence disease challenge tests in Atlantic salmon (Salmo salar)

The aim of the present study was to quantify some of the factors affecting disease challenge experiments in Atlantic salmon. This included estimation of the effect of non-MHC genes and the tank effect. The material was sampled from a MHC homogenous population consisting of three half-sibling groups. The background genome study included two viral and one bacterial challenge trial. In the viral challenge trial using infectious pancreatic necrosis virus (IPNV), 525 fish from three families were randomly sampled and divided into three equally sized replicates. In both the bacterial challenge trial (Aeromonas salmonicida causing furunculosis) and the second viral challenge trial using infectious salmon anaemia virus (ISAV), approximately 130 fish from each of the three families were included. The total prevalence of death in the IPN, furunculosis and the ISA material were 20.0%, 92.4% and 77.5%, respectively. Significant non-MHC genetic effects were detected in all three disease-challenged materials. The non-MHC genetic effect was estimated to be 12.7% [range: 4.1; 19.1] related to IPN, 9.3% [range: 1.4; 13.9] to furunculosis and 7.5% [range: 2.3; 11.2] related to ISA. The tank effect in the IPNV study was estimated to be 6.3% (95% CI: [3.9, 8.7]). In conclusion, the study detected and quantified a non-MHC genetic effect in the IPNV, ISAV and A. salmonicidae challenged materials and a tank effect related to IPN.