Risk-Based Management of Viral Hemorrhagic Septicemia Virus in Minnesota

Viral hemorrhagic septicemia virus (VHSV; strain VHSV-IVb) is an emergent and serious disease of fish in the Great Lakes region of North America. In addition to the numerous large-scale mortality events in wild fish, the emergence of VHSV has resulted in a major regulatory response to protect both farm-raised and wild fish populations. However, characterizing and mitigating risk factors for the continued transmission of VHSV is a difficult task. A semiquantitative risk assessment model was used to focus VHSV management efforts in Minnesota. The risk of VHSV introduction into major watersheds in Minnesota was directly correlated to their proximity to Lake Superior, the only VHSV-positive body of water in the state. Although the current regulations are uniform across Minnesota, the risk varied for specific locations within the watersheds. For example, the introduction of game fish for stock enhancement (a common fisheries management practice) is a significant factor in determining the risk of VHSV introduction into public waters, as is the movement of baitfish. In this analysis, aquaculture facilities with strict biosecurity programs and frequent health inspections received the lowest risk scores and were largely considered as protective or at low risk for VHSV introduction. These results suggest that the current management strategy, based on political boundaries, should be reevaluated. We recommend the creation of a risk-based management strategy based upon the identification of higher-risk watersheds and specific bodies of wa*Corresponding author: [email protected] Received July 22, 2013; accepted November 27, 2013 ter, thus allowing managers to efficiently target surveillance and response activities in Minnesota. Viral hemorrhagic septicemia (VHS) is a highly contagious viral disease that causes high morbidity and mortality in a wide range of marine, brackish, and freshwater fish species (USDA 2008a; Kim and Faisal 2011). The disease is caused by the viral hemorrhagic septicemia virus (VHSV), which belongs to the genus Novirhabdovirus within the family Rhabdoviridae. Due to its significant effect on farmed and wild fish populations, VHSV is listed by the World Organization for Animal Health as a reportable pathogen (OIE 2012). In 2005, a new strain of VHSV (VHSV-IVb) was identified in the Great Lakes (Elsayed et al. 2006; Lumsden et al. 2007). This novel strain spread rapidly through the region, resulting in numerous mass mortality events in wild fish throughout the eastern Great Lakes and inland lakes of Michigan, New York, and Wisconsin (Kim and Faisal 2011; Thompson et al. 2011). Although a large mortality event has not been reported in Lake Superior, the virus has been isolated from Cisco Coregonus artedi near the Apostle Islands (Faisal et al. 2012). The rapid spread of VHSVIVb in the Great Lakes region has consequently heightened 373 D ow nl oa de d by [ U ni ve rs ity o f M in ne so ta L ib ra ri es , T w in C iti es ] at 1 1: 50 1 9 Ja nu ar y 20 16