Robust skin - genetics, vaccination and nutrition

Offentlig prosjektsammendrag

Robust salmon skin- Genetics, vaccine and nutrition Intensive salmon farming involves keeping a large number of fish in net pens at high densities. Unfortunately, this continuously exposes fish to marine parasites and pathogenic microorganisms. Apart from sea lice, which also cause lesions, wound-related mortalities are major welfare problems in farmed salmon. In addition, frequent handling during delousing and treatments against amoebic gill disease (AGD) aggravates the situation. The severity of these problems varies substantially between groups of fish, implying that the health status before treatment, including epithelial integrity, is important. Contrary to mammalian skin, where the epidermis is protected by keratinized dead cells, fish skin is composed of fragile living cells making up the barrier against pathogenic microorganisms and other external stressors. Apart from mechanical and lice related wounds, farmed salmon also develop winter-ulcers when infected with the bacterium Moritella viscosa. Although most common in the northerly regions of Norway, M. viscosa induced winter-ulcers appear nationwide at water temperatures of 10 degrees Celsius or lower. The affected fish may develop deep ulcers and a systemic infection resulting in considerable losses if not treated. Furthermore, infected fish may survive over extended periods, representing a serious welfare issue. This disease is undoubtedly the most economically and biologically important bacterial disease in Norwegian salmon farming, with a difficult to estimate cost probably exceeding 1 billion NOK annually. The project seeks to elucidate the genetics and biology underlying wound healing and Moritella viscosa resistance. Additional experiments have been included in the project to study interactions between genetics and protective immune response after vaccination, and how functional diets may improve wound healing and development of winter ulcers.