Positive genetic correlation between resistance to bacterial (furunculosis) and viral (infectious salmon anaemia) diseases in farmed Atlantic salmon (Salmo salar)

A total of 237,085 individuals, from 2960 different full-sib families, from 11 year-classes, were tested for the bacterial disease furunculosis or viral infectious salmon anaemia (ISA). Challenge-testing for the two diseases was carried out on different individuals of the same full-sib families (106,136 and 130,949 individuals for furunculosis and ISA, respectively). A bivariate sire–dam threshold model was developed for joint analysis of the two traits. The estimated heritabilities for furunculosis and ISA were 0.43 (± 0.02) and 0.32 (± 0.02), respectively, while the genetic correlation was weakly positive (0.15 ± 0.05). Common family (environmental and non-additive genetic) effects were estimated for both traits and explained 11 and 5% of total underlying phenotypic variance in liability for furunculosis and ISA resistance, respectively. The estimated correlation between common family effects of the two traits was positive (0.31 ± 0.07).