Direct and Indirect Evidence Suggests Continuous Presence of Viral Hemorrhagic Septicemia Virus (Genotype IVb) in Budd Lake, Michigan: Management Implications

Abstract

AbstractIn May 2007, viral hemorrhagic septicemia virus genotype IVb (VHSV IVb) was isolated from several fish species in Budd Lake, a 71‐ha inland lake in central Michigan. Because of the virulence and pathogenicity of VHSV IVb, follow‐up testing was conducted between 2007 and 2010. This testing found no further evidence of VHSV IVb presence. Similar patterns (i.e., initial mortality events followed by no evidence of additional infections) have been observed in other waterbodies, which leads to questions regarding the implications that these patterns could have for fisheries management (e.g., could stocking naive fish lead to additional epizootic occurrences?). This study was conducted to determine whether VHSV IVb was still present in Budd Lake by intensively sampling across multiple seasons, locations, and size‐groups of Muskellunge Esox masquinongy, Northern Pike Esox lucius, and Largemouth Bass Micropterus salmoides. Individuals were tested for both active VHSV IVb infection and antibody production. We found that VHSV IVb was still present in Budd Lake, as active infections were detected from samples in spring, summer, and fall 2011, with highest infection prevalence in spring 2011. Spring 2011 infection prevalence was 17% for esocids and 33% for Largemouth Bass. Between 74% and 80% of collected esocids produced antibodies, depending on the sampling season. Antibody production in Largemouth Bass ranged from 12% in spring and fall 2011 to 20% in spring 2012. Based on these results, we recommend sustained vigilance in the management of VHSV IVb–positive systems to limit the risk of virus spread as it is perhaps questionable whether systems that have experienced an outbreak will ever be virus‐free.Received September 16, 2014; accepted February 7, 2015