Ulcerative dermal necrosis of mature Atlantic salmon in the Kola and Tuloma rivers (Murmansk region): retrospective and prospects for studying the problem

The aim of the work is to analyze the results of virological and immunological studies, to track the dynamics of the entry and changes in external signs of pathology of Atlantic salmon into the Kola and Tuloma rivers. Methods used: fish size and weight indicators were determined using generally accepted methods. Methods for isolating viruses on continuous cell lines and their identification in RT-PCR reaction were used. Bactericidal activity of blood serum (BABS) was assessed using a nephelometric method. The content of non-specific immune complexes (IC) was established using a spectrophotometric method with selective precipitation with PEG-6000. According to the results of the work , it was revealed that in the Kola and Tuloma rivers, clinical manifestations of pathologies in fish have changed. Since 2021, typical symptoms of UDN have been replaced by signs of «red skin disease». The results of immunological studies indicate high activity of innate humoral immunity mechanisms in the examined individuals. The carriage of infectious pancreatic necrosis virus in Atlantic salmon populations living in the Kola and Tuloma rivers has been established. Clinical signs of pathology in Atlantic salmon are described in detail, and fish counting data for the Kola and Tuloma rivers are presented. The novelty of the work: for the first time, photographs of all noted typical signs of pathology, as well as the results of virological and immunological studies of Atlantic salmon in the Kola and Tuloma rivers for 2022–2024 are presented. A retrospective overview is given and prospects for studying the problem are outlined. Practical significance: the conducted research will allow creating a database on the results of comprehensive studies of Atlantic salmon diseases in the Kola and Tuloma rivers. Compare the results obtained in fish with and without clinical signs of pathologies over several years. Determine differences in the immune status of fish with different signs of pathology based on the results of long-term studies. This will help to understand how UDN disease develops over time and what causes it.