Monitoring and assessing risk for VHS in Minnesota waters
When you picture an aquatic invasive species, what comes to mind? Probably the small-but-problematic zebra mussel, a swath of Eurasian water milfoil, or perhaps the ubiquitous common carp. What may not come to mind, however, is a harmful fish pathogen called Viral Hemorrhagic Septicemia Virus (VHSV).
Like other invasive species, it is non-native and was introduced to the area, it moves through different ecosystems with ease, and it has the potential to cause great ecological and economic harm. Unlike other invasive species, it’s a pathogen that has the ability to travel through water independent of its host and can therefore be very difficult to monitor.
VHSV can cause high mortality rates in both farmed and wild fish populations, making it of great concern to aquaculturists and recreationalists alike. As the name describes, visible symptoms often include hemorrhaging throughout the fish, which is not only unsightly, but can result in organ failure and eventual death. VHS was first found in the upper Midwest nearly ten years ago, and it has since been found in all five Great Lakes and inland lakes of Ohio, Michigan, New York, and Wisconsin – but not in inland waters in the state of Minnesota – and MAISRC researcher Dr. Nick Phelps would like to keep it that way.
Phelps, an Assistant Professor in the University of Minnesota’s College of Veterinary Medicine, has worked with the Minnesota Aquatic Invasive Species Research Center since its inception. One primary project has been to conduct surveillance and risk assessment projects to help further understand VHS’s effects on Minnesota.
Through surveillance work, Phelps and his team can establish where the virus can and can’t currently be found. Luckily, VHSV has not yet been found in inland waters of Minnesota. However, by conducting a risk assessment, they can identify places in Minnesota where the virus is most likely to appear, which can help prioritize management and control efforts. Risk is determined through a variety of factors, such as connectivity to infected waters, conducive water temperatures, linear distance to infected waters, and nearby boater movement. Learn more about Dr. Phelps’ research in this article, “Risk-Based Management of Viral Hemorrhagic Septicemia Virus in Minnesota.”
Figure above: Map of the risk of VHSV introduction into Minnesota watersheds. Numbers within the watersheds identify the watersheds based on four-digit hydrologic unit codes. The darker the shading, the higher the risk of VHSV introduction.
Presently, 34 different species of fish can be infected by the Great Lakes strain of the virus. Humans and other animals are not known to be susceptible to the disease. However, researchers have discovered that while zebra mussels cannot be infected by the virus, they can carry it and act as a vector to infect other waters.
To help prevent the spread or introduction of VHS, follow basic aquatic invasive species rules: always clean your boat, dispose of your bait and bait water, and don’t move fish between water bodies. If you observe a fish kill or catch a fish you suspect may be diseased, please contact the DNR.