Moritella viscosa is the causative organism. The pathogenicity is magnified by the concurrent presence of Aliivibrio wodanis. The popular name of Salmon Winter Ulcer disease is given because it mostly manifests itself during winter months in the Northern hemisphere, when the water temperature falls to 8 -10 Celsius
When an outbreak occurs, it typically results in considerable losses, and even those fish that survive, show visible severe scarring, that makes them unsaleable. The losses in Norway alone have been calculated in some seasons to approach 100 million Krone. The infection affects both Salmon and also Rainbow Trout.
The only treatment known to date is the use of vaccines. However apart from the cost and stress of such, the outcomes have not been overly successful and even when they appeared promising, the lasting effect was not permanent.