Risk factors perceived predictive of ISA spread in Chile: applications to decision support

Area of Science:

• Aquaculture
• Fish Health
• Disease Epidemiology

Background:

• Aquaculture is vital for global food security, but diseases like infectious salmon anemia (ISA) threaten its sustainability.
• ISA outbreaks have historically led to significant industry and regulatory changes, as seen in Chile.
• Universal disease mitigation strategies were implemented in Chile, reducing ISA incidence but leaving the efficacy of individual measures unclear.

Purpose of the Study:

• To identify and weight risk factors predicting the introduction and spread of ISA virus (ISAV) between Atlantic salmon farming neighborhoods (barrios) in Chile.
• To provide expert-driven decision support for disease prevention and sustainable aquaculture practices in the absence of extensive field data.
• To inform policy and industry best practices for ISA management.

Main Methods:

• Convened a panel of fish health experts to assess risk factors for ISAV occurrence in Chilean salmon farming barrios.
• Focused on barrios as the unit of analysis due to the scale of implemented mitigation strategies.
• Validated expert estimates with field data on ISAV and associated risk factors post-panel assessment.

Main Results:

• Experts identified barrio processing plant biosecurity, fallowing, live fish transfers, density, smolt quality, hydrographic connectivity, sea lice, and harvest vessel biosecurity as key predictors for virulent ISAV (HPR-deleted).
• Fewer factors predicted HPR0 ISAV, with fish/site density, adult live fish transfers, and smolt facility HPR0 status being most significant.
• Field validation generally supported expert predictions, with some factors like broodstock HPR0 status requiring further investigation.

Conclusions:

• Expert opinion provides valuable insights for ISA virus (ISAV) risk assessment and management in aquaculture.
• Key factors influencing ISAV spread include biosecurity, fish density, and management of live fish transfers.
• Findings support the refinement of legislation, best management practices, and surveillance strategies for sustainable salmon aquaculture.