In 2021, the United States Department of Agriculture’s (USDA) National Animal Disease Preparedness and Response Program funded the first proposal to focus on disease risk in the aquaculture sector. Specifically, the funded project aimed to assess the risks of spreading Viral Hemorrhagic Septicemia virus (VHSV) IVb in Great Lakes region associated with moving live fish from a fish farm or hatchery. A virus with a complex history in the Great Lakes basin, VHSV IVb was first detected in 2005 in wild fish, and a cascade of regulatory action was quickly enacted at the federal- and then state-level. The USDA quickly instituted a stop movement order of live fish, including those cultured by private, public, and tribal fish producers, across state lines. After push back from fish producing stakeholders against the agency’s decision, the USDA amended the order and gave state natural resource and/or agriculture agencies jurisdiction over managing live fish movements.
As of 2024, state agencies take some varied approaches to managing fish movements with specific requirements in place to potentially curb the spread of VHSV IVb. Additionally, detections of VHSV IVb still occur annually in wild fish in isolated areas in the Great Lakes Basin and detection of the virus has occurred in wild broodstock of salmonid species at spawning weirs; however, there has never been a detection of the pathogen on a fish farm or hatchery. Because of the absence of detections in propagated fish populations, continued sporadic detections of the virus in wild populations, and the consequences of the detecting the virus on a farm or hatchery, perceptions of disease introduction risk vary among stakeholders.
To this end, a regional VHSV risk assessment was conducted, which included the evaluation of the likelihood of VHSV entry onto Great Lakes fish hatcheries. Likelihood of VHSV entry was evaluated using a framework adapted from the World Organisation of Animal Health (WOAH) Import Risk Analysis methods as well as from Secure Food Systems Proactive Risk Assessment methodology. Specific disease entry pathways onto fish hatcheries were identified and systematically evaluated through the qualitative synthesis of input provided by a Great Lakes Public and Tribal Fish Hatchery workgroup as well as available scientific literature related to known host-pathogen-environment interaction mechanisms. Throughout this process biosecurity gaps on fish hatcheries were identified based on workgroup input and additional pathogen-specific mitigations were determined. Upon completion of the final step, the likelihoods of VHSV entry were assigned ratings using a likelihood rating scale utilized by the World Organization for Animal Health for risk analysis.
While results of the risk assessment are specific to public and tribal fish hatcheries, here we discuss how results have been adapted to inform risk-based biosecurity that commercial fish farms can implement if they are in a VHS-high risk scenario. Additionally, findings from the risk assessment have been translated into a tool that can help fish producers determine what constitutes a VHS-high risk scenario.