Research Highlights

Molecular Epidemiology of Viral Hemmorrhagic Septicemia Virus in the Great Lakes Region

Yellow perch experimentally infected with a Great Lakes strain of VHSV. These fish show high mortality with typical signs of disease. Photo courtesy of the USGS Western Fisheries Research Center.

Viral hemorrhagic septicemia virus (VHSV) is considered by many nations and international organizations to be one of the most important viral pathogens of finfish (Office International des Epizooties 2007). For several decades following its initial characterization in the 1950s, VHSV was thought to be limited to Europe where it was regarded as an endemic pathogen of freshwater fish that was especially problematic for farmed rainbow trout, an introduced species (Wolf 1988; Smail 1999). Subsequently, it was shown that VHSV was present among many species of marine and anadromous fishes in both the Pacific and Atlantic Oceans where it has been associated with substantial mortality among both wild and cultured fish (Meyers and Winton 1995; Skall et al. 2005).

Beginning in 2005, reports from the Great Lakes region indicated that VHSV had been isolated from fish that had experienced very large die-offs in the wild (Elsayed et al. 2006; Lumsden et al. 2007; Groocock et al. 2007). By the end of 2007, VHSV had been isolated from more than 25 species of fish in Lake Michigan, Lake Huron, Lake St. Clair, Lake Erie, Lake Ontario, Saint Lawrence River and from inland lakes in New York, Michigan and Wisconsin (Figure 1). The Great Lakes strain of VHSV appears to have an exceptionally broad host range and significant mortality has occurred in muskellunge, freshwater drum, yellow perch, round goby, emerald shiners and gizzard shad.

Fisheries managers in the US and Canada are concerned about the spread of this highly virulent strain of VHSV from the Great Lakes region into new populations of native freshwater fish or into new geographic areas. Furthermore, the introduction of VHSV into the aquaculture industry could cause additional trade restrictions as well as direct lossesfromdisease.

In recent years, the tools of molecular biology have provided new insights into the ecology and epidemiology of many viruses of humans and animals. Scientists from the USGS Western Fisheries Research Center (WFRC) have been successfully using molecular analyses to better understand the distribution and spread of VHSV. For a review of their work, see the full Fact Sheet: Molecular Epidemiology of Viral Hemmorrhagic Septicemia Virus in the Great Lakes Region (26 KB, PDF - get free Adobe Reader).