Pasteurellosis

Pasteurellosis is a bacterial disease affecting various fish species in aquaculture, including Atlantic salmon (Salmo salar), lumpsucker (Cyclopterus lumpus), and other marine fish. It is caused by bacteria of the family Pasteurellaceae, particularly Pasteurella skyensis and other related species. The disease has emerged as a significant concern in salmon farming in Norway and Scotland, leading to high mortality rates and economic losses. Pasteurellosis in fish was first identified in Norway in 1989 and has become increasingly prevalent in recent years, with approximately 50 diagnosed cases registered annually in farms in south-western Norway from 2020 to 2022 5.

• Physical Signs:

  • Septicemia: Systemic bacterial infection affecting multiple organs 12.
  • Hemorrhages: Reddened areas on internal organs 3.
  • Exophthalmia: Bulging or protruding eyes may occur in some cases 3.
• Behavioral Changes:

  • Lethargy: Reduced activity and sluggish swimming 2.
  • Loss of Appetite: Decreased feeding behavior 2.
  • Abnormal Swimming Patterns: Fish may swim sluggishly and in random patterns 2.

Progression of Symptoms

• Early Stages: Subtle signs such as reduced feed intake and slight lethargy.

• Advanced Stages: More pronounced physical symptoms such as septicemia and increased mortality 12.

• Impact on Fish Health: Pasteurellosis severely compromises overall health and can lead to significant mortality if left untreated 12.

Etiology

• Causative Agent: Various Pasteurella species, including Pasteurella skyensis and other related bacteria of the Pasteurellaceae family 125.

• Transmission Methods:

  • Waterborne: The bacterium can spread through water, especially under conditions of poor water quality 2.
  • Potential transmission between species: Concerns about transmission between lumpsucker and Atlantic salmon in aquaculture settings 14.

Risk Factors

• Environmental Factors: Stress conditions, such as delousing treatments, can increase susceptibility to Pasteurellosis 2.

• Farm Management Practices: Use of cleaner fish (e.g., lumpsucker) for delousing may contribute to the spread of the disease 14.

Diagnostic Methods

• Clinical Examination: Observation of physical and behavioral symptoms 2.

• Laboratory Tests:

  • Bacterial Culture: Isolation and identification of Pasteurella species from tissue samples 2.
  • MALDI-TOF MS: Mass spectrometry for rapid identification of bacterial species 2.
  • Whole Genome Sequencing: For precise identification and discrimination of Pasteurella strains 25.

Differential Diagnosis

• Distinguishing Pasteurellosis from Other Diseases: It is crucial to differentiate Pasteurellosis from other bacterial diseases with similar symptoms 2.

Treatment Options

• Current Treatments:
  • Antibiotics: Administered through feed, but may have limited efficacy due to reduced appetite in affected fish 2.
  • Alternative Methods: Injection of antibiotics may be considered for smaller populations or valuable fish 2.

Preventive Measures

• Biosecurity Protocols:

  • Implementing strict biosecurity measures to prevent the introduction and spread of Pasteurella species 2.
  • Regular monitoring and rapid diagnosis of suspected cases 2.
• Farm Management Practices:

  • Careful consideration of cleaner fish use and potential disease transmission 14.
  • Proper cleaning and disinfection of equipment between treatments 2.

Real-World Examples

• Notable Outbreaks:

  • Norway (2020-2022): Approximately 50 diagnosed cases annually in south-western Norway 5.
  • Scotland: Outbreaks associated with Pasteurella skyensis serotype O2 2.
• Response Strategies and Outcomes:

  • Norway: Increased focus on rapid diagnosis and identification of Pasteurella strains 25.
  • Scotland: Development of serotyping methods for _P. skyensis 2.

• Lessons Learned: The importance of routine bacteriology, rapid diagnosis, and proper biosecurity measures in controlling Pasteurellosis outbreaks 25.

Recent studies on Pasteurellosis in salmonids have focused on various aspects of the disease:

1. "Pasteurella skyensis in Atlantic salmon (Salmo salar L.) in Western Norway"
   Authors: Strøm S, Nilsen H
   Reference: EAFP Bulletin, 2023
   Link to study
2. "Pasteurella spp. Infections in Atlantic salmon and lumpsucker"
   Authors: Sandlund Nina, Rønneseth Anita, Ellul Rebecca Marie, Nylund Stian, Sandlund Liv
   Reference: Journal of Fish Diseases, 2021
   Link to study
3. "Phylogeography and host specificity of Pasteurellaceae pathogenic to farmed salmonids and cleaner fish"
   Authors: Gulla S, et al.
   Reference: NCBI PMC, 2023
   Link to study

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Last Modified: 2024-07-26

Tags: #Pasteurellosis, #Salmonoids, #Salmon, #AtlanticSalmon, #Lumpsucker, #Norway, #Norway, #Scotland, #BacterialDiseases, #Bacteria