Winter Wounds

Physical Signs:

• Skin Lesions: Open sores or ulcers on the skin, often starting on the scales and potentially reaching muscle tissue 24.
• Inflammation: Reddened and swollen areas around the wounds.
• Superficial to Deep Wounds: Ranging from superficial wounds to deep ulcers affecting muscle tissue 24.

Behavioral Changes:

• Reduced Activity: Fish may show signs of discomfort and reduced mobility due to wounds.

Early Stages: Bacteria attach to the surface of scales, multiplying and forming colonies between the mucous layer and scales 24.

Advanced Stages: Wounds become larger and deeper, potentially reaching muscle tissue if left untreated 24.

Impact on Fish Health: Winter wounds compromise the fish's skin barrier, making them more susceptible to infections and reducing overall vitality.

Clinical Examination: Observation of physical symptoms, such as skin lesions and ulcers.

Laboratory Tests:

• Bacterial Culture: Identifying Moritella viscosa and its various strains 24.
• Histopathology: Examination of wound tissues to assess the extent of damage and infection.

Current Treatments:

• Vaccines: Several vaccines against different Moritella viscosa strains are available, though efficacy varies 24.
• Preventive Measures: Use of laser technology to kill sea lice, reducing the need for handling fish 1.

Supportive Care:

• Reduced Handling: Minimizing physical trauma through gentle handling practices 1.

Biosecurity Protocols:

• Implementing strict handling procedures to minimize physical trauma 1.
• Regular monitoring of fish health to detect and address early signs of wounds.

Farm Management Practices:

• Developing internal control systems to safeguard fish welfare 1.
• Strategic use of bacteriophages, probiotics, and special feed to reduce risk 1.
• Continuous development and introduction of new vaccines 124.

Notable Outbreaks:

• Norway: Winter wounds are a significant concern for Norwegian salmon farms, causing substantial economic losses estimated at $750 million annually 13.

Response Strategies and Outcomes:

• Norway: Strengthening cooperation with professional authorities to address the issue 1.
• Development of new vaccines and improved vaccination strategies 124.
• Research into understanding causal relationships and managing risks associated with winter wounds 14.

Lessons Learned: The importance of systematic approaches to understanding causal relationships, uncovering adverse developments, and taking timely measures 14. The need for continuous research and development of effective vaccines against various strains of Moritella viscosa 24.

Winter Wound Management in Norway:

• Winter wounds are a significant problem for farmed salmon in Norway, particularly during cold seawater conditions 12.
• The bacterium Moritella viscosa is the primary cause of these winter ulcers 1 2.

Recent Developments:

• Researchers at Nofima have made breakthroughs in understanding salmon skin and vaccine efficacy 14.
• New knowledge about how the bacterium colonizes salmon skin has been discovered 12.

Economic Impact:

• Winter wounds lead to financial losses due to fish mortality and downgrading of slaughtered fish 1.

Treatment & Management:

• Vaccination is possible but challenging due to multiple strains of Moritella viscosa 12.
• Several vaccines against different Moritella viscosa strains are now available on the market 12.
• Preventive measures include using laser technology to kill lice, which may indirectly reduce winter wound occurrence 1.