Risk based health monitoring of wild finfish in Norway 2022. Surveillance program report. Norwegian Veterinary Institute report 10_2023.
Research report
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https://hdl.handle.net/11250/3079563Utgivelsesdato
2023Metadata
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Sammendrag
A national notification portal for disease and mortality in wild fish was established in 2020 in cooperation between NVI and the Norwegian Food Safety Authority (NFSA).The main purpose of this portal is to facilitate early detection of serious disease in wild fish by simplifying the reporting procedure. The reports themselves and the subsequent diagnostic work provide an insight into the health of wild fish. In addition, health problems that are candidates for further attention through surveillance and monitoring are identified. The notification portal has thus become an integral part of health monitoring of wild fish both in freshwater and in the marine environment. From 2022, the notification portal was linked to the NFSA health monitoring program in order to investigate the presence of cultivable virus and bacteria in wild fish reported. Accordingly, samples were mainly collected during disease outbreaks in wild populations, but also from individual fish showing adverse behaviour or other signs of ill health. No viruses were detected by cultivation in selected cell lines, nor by specific qPCR. Listed bacterial diseases were not detected by cultivation of bacteria on growth media, nor by specific qPCR. Classic vibriosis, caused by Vibrio anguillarum, was detected in wild Atlantic salmon (Salmo salar) in two rivers, Lysakerelva and Nordmarkselva (Akerselva), both draining to the inner Oslo fjord (Oslo County). In Lysakerelva number of reported dead Atlantic salmon was 60, while the mortality in Nordmarkselva was not estimated, but significantly lower than in Lysakerelva. Mycobacteriosis, caused by Mycobacterium salmoniphilum was detected in a wild cod (Gadhus morhua) in the fjord Eidsfjorden, Vestland County. In a number of rivers, there was high mortality among spawners due to saprolegniosis caused by Saprolegnia parasitica. In several of the affected fish, examinations showed growth of bacteria that are considered to be opportunistic pathogens. These bacteria were generally not isolated in pure cultures. This may indicate that the diseased individuals were infected due to a suppressed immune system or impaired barriers caused by lesions in the skin. The impact of the bacterial infections on the individual fish in the specific cases remain uncertain. Risk based health monitoring of wild finfish in Norway 2022. Surveillance program report. Norwegian Veterinary Institute report 10_2023.