Winter Wounds

Winter wounds, also known as winter ulcers or winter sores, are a common condition affecting farmed Atlantic salmon (Salmo salar), typically occurring during the colder months. These wounds are primarily caused by bacterial infections, particularly Moritella viscosa, and are exacerbated by cold water temperatures, significantly impacting fish health and welfare 12. Winter wounds are prevalent in salmon farming regions with colder climates, such as Norway, Scotland, and Canada. While primarily affecting Atlantic salmon, other salmonid species can also suffer from similar conditions under cold water temperatures.

• 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.

Progression of Symptoms

• 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.

Etiology

• Primary Cause: Bacterial infection, predominantly by Moritella viscosa 124.
• Environmental Factors: Cold water temperatures (8°C or lower) increase susceptibility to infections 4.
• Secondary Infections: Other opportunistic pathogens can infect open wounds, exacerbating the condition.

Risk Factors

• Environmental Factors: Cold seawater temperatures, particularly during winter months 124.
• Farm Management Practices: Handling of fish for sea lice treatments may contribute to the problem 1.

Diagnostic Methods

• 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.

Differential Diagnosis

• Distinguishing Winter Wounds from Other Conditions: It is crucial to identify the specific strain of Moritella viscosa for effective treatment and vaccination 24.

Treatment Options

• 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.

Preventive Measures

• 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.

Real-World Examples

• 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.

Recent studies on winter wounds in salmonids have focused on various aspects of the disease, including its prevention, control, and economic impact. Here are some notable recent research findings:

1. "Vaccinating salmon against winter ulcers"
   Authors: Karlsen, C. R., et al.
   Reference: Nofima (2023). Vaccinating salmon against winter ulcers.
   Link to study
2. "Norwegian researchers in the battle against winter ulcers in salmon"
   Authors: Nofima researchers
   Reference: We Are Aquaculture (2023). Norwegian researchers in the battle against winter ulcers in salmon.
   Link to study

These findings highlight the ongoing challenges in managing winter wounds in farmed salmon and the importance of continued research and vaccine development to improve fish health and reduce economic losses in the aquaculture industry.

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Last Modified: 2024-08-14

Tags: #FishDisease, #WinterWounds, #Salmonoids, #AtlanticSalmon, #Trout, #ArcticChar, #Norway, #Scotland, #BacterialDiseases, #Bacteria, #MoritellaViscosa, #Tenacibaculummaritimum