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"Aquaculture, not the Internet, represents the most promising investment opportunity of the 21st Century."

- Peter Drucker, Management Expert & Economist


Virus Y - a "new disease" in rainbow trout

A new disease is described in freshwater rainbow trout in Norway. A new virus is detected in diseased fish, but not yet confirmed as the causal agent of the disease.

In late August 2013 the Norwegian Veterinary Institute (NVI) received the first case of diseased rainbow trout from a hatchery. The signs of disease were unusual for fish at this age. The second and third cases were submitted to the NVI during October and primo November. The most recent hatchery affected by this disease was recorded in January 2014. Diseased fish were sized from 30 - 100 g. One hatchery reported high mortality in some pens. The other affected sites reported moderate mortalities.

Diseased fish were exposed to freshwater or water with low salinity (< 1‰).  Fish from hatcheries affected by the disease were transferred to seawater. In one case high mortality after seawater transfer was reported, but the mortality ceased after a short period. Two farms have experienced disease two to three months after sea transfer. In other cases no specific problems in sea water have been recorded.

The fish farmers involved have from a preventive perspective and after having consulted the Norwegian Food Safety Authority (NFSA), carried out measures to mitigate the risk of spreading the disease.

Disease signs
Sick fish show signs of circulatory failure and may have pale viscera due to anaemia. Ascites may also be observed. Histopathological findings are inflammation in heart- and red muscle tissue and cellular necrosis in the liver.

Follow the development in this new disease at the homepage of Norwegian Veterinary Institute.

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