A new system for monitoring health status in Norwegian aquaculture.

In Norway there is an official system (ANISTAT) for reporting notifiable diseases to the Norwegian Food Safety Authority, which is mainly done by veterinarians and laboratories. Another separate official system (HAVBRUKSDATA) is also in place, for reporting production data from fish farms, such as the number of fish put into the sea, and their weight, density, feed consumption and mortality. The reported data are aggregated monthly with information from companies' private databases related to each production site and each production unit. There also are official procedures in place for the registration of drugs used in aquaculture, based on veterinary prescriptions. However there is no electronic system for active reporting diseases influencing production and/or welfare. It is our aim to establish a more advanced official system for monitoring the health situation in Norwegian fish farms (MFISK) by linking relevant production data from the various private databases to an official disease database. The output of the new system will be improved statistics on diseases in the Norwegian fish farming industry, with diseases sorted by their impact on production and welfare. This will enable us to identify diseases that, over time, cause such losses that they should be dealt with by the authorities, or by the farmers themselves. It will also have an early warning function regarding new/emerging diseases or disease trends. This system quantifies losses due to health problems and, in the long run, will be a useful tool for strengthening fish health. The system aims to combine data from various sources: the veterinary and fisheries authorities in Norway, farmers, veterinarians and laboratories. To be sustainable, it will need the active and constructive cooperation of all these stakeholders.

Platyspondyly and shortness of vertebral column in farmed Atlantic salmon Salmo salar in Norway--description and interpretation of pathologic changes.

Body malformation due to shortness of the vertebral column, in most cases of unknown cause, has been observed in fish for more than 100 yr. It periodically occurs with high prevalence in farmed Atlantic salmon Salmo salar in Norway, and this paper describes the results of macroscopic, radiographic and histologic examination of parr and seawater-transferred fish. The vertebral bodies in both age groups did not acquire the length that they normally should due to a growth disturbance leading to the condition of platyspondyly and shortness in the column. The pathologic changes became visible at different ages in both groups and the process apparently starts in intervertebral tissues. There was proliferation of connective tissue and blood vessels, and sometimes infiltration with inflammatory cells, around affected vertebrae, especially in seawater-transferred fish. This is the first description of inflammation in abnormally short-spined fish, and it may indicate an infectious etiology, at least in farmed seawater-transferred salmon.

A morphological study of the gross and light microscopic lesions of infectious anaemia in Atlantic salmon (Salmo salar).

Infectious anaemia in Atlantic salmon (Salmo salar) was studied by recording gross and light microscopic changes, and the development of lesions was studied in relation to haematocrit values. Gross lesions were characterised by ascites formation, congestion and enlargement of liver and spleen, congestion of the foregut and petechiae in the peritoneum. Histologically, lesions were demonstrated in the liver, being characterised by congestion in early stages (that is, haematocrit values around 25), dilatation of the sinusoids, and in later stages (haematocrit values 25 to 15) formation of blood-filled spaces bearing morphological resemblance to peliosis hepatis. At low haematocrit values (around 10), these changes comprised large areas of the liver parenchyma, that is, blood-filled areas coalesced, presenting islets of degenerate and necrotic hepatocytes. At this stage, haemorrhagic necroses were found. Spleen and kidney lesions were characterised by congestion. In the foregut, congestion and bleeding in lamina propria were observed. Liver lesions became more disseminated and severe with decreasing haematocrit values. Hypoxia due to anaemia alone cannot fully explain the development of the liver lesions.