Role of the Round Goby in the Maintenance and Spread of VHSV IVb in the Great Lakes

Viral hemorrhagic septicemia virus (VHSV) is a virulent pathogen affecting fish worldwide.  In the Great Lakes, VHSV has caused large mortality events in many species, including round gobies (Neogobius melanostomus).  Round gobies are an invasive species in the Great Lakes and multiple years of surveillance have demonstrated that this species has a disproportionately high prevalence of VHSV.  Additionally, seasonal variations in viral prevalence and the unique life history characteristics of the round goby made it the ideal candidate for intensive studies of infection dynamics in the field and laboratory.  We determined the median lethal dose for naïve and previously exposed round gobies and found that they are highly susceptible to VHSV infection and that previous exposure significantly decreases mortality.  We sampled round gobies in over-wintering locations in offshore waters of Lake Ontario and found a low prevalence of VHSV in offshore populations.  We also implemented a mark-recapture study with round gobies to track changes in prevalence over time and found wide fluctuations in viral prevalence over very short periods of time.  The results from these studies suggest that round gobies may play a key role in the maintenance and spread of VHSV in the Great Lakes.