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

Abstract

In 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

Potential Reservoirs and Risk Factors for VHSV IVb in an Enzootic System: Budd Lake, Michigan

“…The positive virus detection in amphipods and stocked Largemouth Bass held in enclosures lends support to the contention that Budd Lake, Michigan, continues to be enzootic for VHSV IVb (Throckmorton et al 2015). Throckmorton 2015) isolated VHSV IVb from Largemouth Bass and esocids in 2011, which coincided with our enclosure study and the first year of amphipod collection.…”

“…Throckmorton 2015) isolated VHSV IVb from Largemouth Bass and esocids in 2011, which coincided with our enclosure study and the first year of amphipod collection. However, it is of interest to note that Throckmorton et al (2015) did not find any indication of virus presence in Largemouth Bass in spring 2012, even though in this study, we detected VHSV IVb in amphipods during the same time period. The taxonomic identification of the positive amphipod pools from 2011 is unknown; however, all positive samples in 2012 belonged to the family Hyalellidae.…”

“…For example, in Lake St. Clair, VHSV IVb was identified only in fish samples from 2003, 2006, and 2009, even though the lake was inspected often . Similarly, in Budd Lake, Michigan, VHSV IVb was detected in 2007 and 2011, but sampling conducted in intervening years failed to confirm the continuous presence of the virus Throckmorton et al 2015;M. Faisal, unpublished data).…”

“…In May 2011 (coincidentally on the same day that the enclosure study described below began), a mortality event occurred on Budd Lake involving Bluegills and Largemouth Bass, but VHSV IVb could not be isolated from any of the collected samples (Faisal, unpublished data). However, shortly thereafter, active VHSV IVb infections were isolated in apparently healthy esocids (Muskellunge and Northern Pike E. lucius) and Largemouth Bass at prevalences of 14% and 10%, respectively (Throckmorton et al 2015).…”

Genomic and immunogenic changes over the history of the Viral Hemorrhagic Septicemia (VHS-IVb) fish virus (=Piscine novirhabdovirus) in the Laurentian Great Lakes

“…532 Wayne County, Michigan, which is adjacent to Lake St. Clair that is a highly urbanized area with 533 the largest number of registered anglers in the state [91]. Anglers traveling from that area to 534 Budd Lake may have unknowingly transported VHSV, perhaps via live bait [12,14,92]. 535…”