PRV-1 Virulence in Atlantic Salmon Is Affected by Host Genotype

Area of Science:

• Aquaculture
• Fish Pathology
• Virology

Background:

• Heart and skeletal muscle inflammation (HSMI) significantly impacts Atlantic salmon production in Norway, caused by piscine orthoreovirus genotype 1 (PRV-1).
• Regional variations in HSMI disease severity are suspected to stem from genetic differences in PRV-1 strains.

Purpose of the Study:

• To investigate the influence of PRV-1 isolates and Atlantic salmon host genetics on HSMI disease outcomes.
• To determine if viral isolate or host genotype is a more significant factor in HSMI disease variation.

Main Methods:

• Controlled laboratory injection challenges were performed using three distinct PRV-1 isolates (two PRV-1a, one PRV-1b).
• Atlantic salmon from three different stocks (Scotland, Western Canada, and New Brunswick) were challenged with the PRV-1 isolates.
• Virus replication, host response, and heart inflammation severity were assessed to compare disease outcomes.

Main Results:

• Significant variations in disease outcomes were observed among the PRV-1 isolates and Atlantic salmon stocks.
• Atlantic salmon stock influenced heart inflammation severity, irrespective of the PRV-1 isolate used.
• New Brunswick salmon exhibited less heart inflammation compared to Western Canadian and Scottish salmon, indicating a host genetic effect.

Conclusions:

• The presence of specific PRV-1 genotypes (PRV-1a or PRV-1b) alone does not reliably predict HSMI disease severity.
• Atlantic salmon host genotype plays a crucial role in modulating HSMI disease severity.
• Understanding host genetic factors presents a potential strategy for mitigating HSMI disease impact in aquaculture.