Predictive factors and viral genetic diversity for viral hemorrhagic septicemia virus infection in Lake Ontario and the St. Lawrence River

Viral hemorrhagic septicemia virus (VHSV) is the causative agent of a devastating disease in fish, viral hemorrhagic septicemia (VHS), which has recently spread to the Laurentian Great Lakes. In this paper, we report the results of infection surveillance conducted during 2009 for VHSV with a focus on yellow perch (Perca flavescens) and round goby (Neogobius melanostomus). We collected 1928 fish representing eight species at nine sites in Lake Ontario and the St. Lawrence River and found fish positive for VHSV by quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) at every site. Prevalence of virus-positive fish at individual sites ranged from 0.7% to 27.5%. Yellow perch were significantly less likely to test positive than round goby in this study. In logistic regression models, maturity was a significant predictor of testing positive in yellow perch, but no evaluated factor was a significant predictor of testing positive in round goby. Virus isolation in cell culture was successful in seven out of 37 high titer fish samples, and partial glycoprotein gene sequences obtained from these virus isolates showed an increase in genetic diversity relative to the previously known diversity of Laurentian Great Lakes VHSV genotype IVb. These results highlight the importance of continued movement restrictions and surveillance for VHSV in wild fish in the Laurentian Great Lakes as well as suggest future work to further elucidate the infection dynamics of this virus in wild fish populations.