Photo credit: New York State Department of Environmental Conservation (NYSDEC)
Viral Hemorrhagic Septicemia (VHS)
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Species at a Glance
Viral hemorrhagic septicemia (VHS) virus is a highly contagious fish pathogen that has caused significant fish kills in the Great Lakes region of the United States and Canada. Once a fish is infected with VHS, there is no known cure.
VHS is a bullet-shaped virus of the genus Novirhabdovirus. Symptoms of the disease may include bulging eyes, bloated abdomens, darker coloration, unusual behavior, and hemorrhaging in the eyes, muscle tissue, skin, gills, and at the base of the fins. Some species, such as the bluntnose minnow (Pimephales notatus) and the emerald shiner (Notropis atherinoides) show no obvious symptoms.
The symptoms of VHS have characteristics similar to those of other fish diseases, so lab testing is necessary to confirm that a fish is infected with VHS.
Fish mortality from VHS infection is highest at water temperatures between 9-12°C (48-54°F), and deaths rarely occur at temperatures above 15°C (59°F). Outbreaks often occur during stressful environmental changes, such as rising water temperatures in the spring, or during spawning.
VHS is highly contagious and easily transmissible, spreading through contact with the infected water or from fish to fish. Survivors can become lifelong carriers. Transfer to new water bodies is thought to be primarily through fish stockings and baitfish transfer. Natural fish migrations, recreational boating and angling, ballast water discharge, and aquarium and live fish releases could also help spread this virus.
Since its initial discovery in Europe in the mid-1900s, four VHS strains, including freshwater and marine, have been identified. Introduction into the Great Lakes is believed to have been as early as 2003. VHS is present in the waters of lakes Michigan, Huron, St. Clair, Erie, and Ontario, as well as the Detroit, Niagara, and St. Lawrence rivers and in some of the Finger Lakes in New York.
Note: Distribution data for this species may have changed since the publication of Pennsylvania's Field Guide to Aquatic Invasive Species (Second Edition 2015), the source of information for this description.
At least 50 species of marine and freshwater fish carry the virus, including muskellunge, smallmouth bass, northern pike, and yellow perch. View a full list of VHS-susceptible species. The long-term risks of VHS on the Great Lakes’ four billion dollar fishery are unclear; however, large fish kills of certain species have been reported. There is no indication that VHS is a threat to human health.
Note: In Pennsylvania, live fish transport out of the Lake Erie and Genesee River drainage basins is prohibited. It is also unlawful to transport, sell, or introduce VHS susceptible species, dead or alive, into the Commonwealth unless laboratory tested and certified as negative for the virus. It is also unlawful in Pennsylvania to use the eggs of VHS-susceptible species as bait.
Information for this species profile comes from Pennsylvania's Field Guide to Aquatic Invasive Species (Second Edition 2015).