Viral hemorrhagic septicemia (VHS) is a fish disease of global concern that was first confirmed in the Great Lakes in 2003. The emergence of this invasive virus has resulted in large-scale mass mortality events throughout the eastern Great Lakes and cost millions of dollars in management efforts. The virus is considered by many to be the most significant freshwater fish health threat in the world and has a history of large-scale fish kills.

The University of Minnesota is a leader in Viral Hemorrhagic Septicemia virus research and outreach efforts focused on early detection and prevention. Click here to download a factsheet about pathogens and harmful microbes research at MAISRC.

About VHS

Life cycle

The strain of VHSV in the Great Lakes (VHSV-IVb) is particularly active in cool waters (5-20C) and can survive outside of the host at ideal temperatures (~10C) for weeks. The virus is transmitted fish-to-fish from close contact of contaminated water or reproduction. The virus can also be transmitted on the surface of the egg to be passed from parent to progeny.

What it affects

In the Great Lakes, 34 species of fish have been found positive from natural infections. This includes many of the popular game fish species such as Walleye, Muskellunge, Salmonids, and Bass. The reservoir species (e.g. maintains virus persistence in the environment) in the Great Lakes appears to be another invasive species, the Round Goby.

Where it's found

VHSV has been confirmed in all of the Great Lakes, in some inland waters of Michigan (Budd Lake), New York (several finger lakes), and Wisconsin (Lake Winnebago). The virus has not been detected in inland waters of Minnesota, however Lake Superior is known to be infested.

How it spreads

The virus can spread from one location to another via direct fish/water movement (i.e. connected waters), transfer of infected fish (i.e. stocking, baitfish), and contaminated water and gear (i.e. boaters, anglers). Proactive measures to test fish to certify freedom of disease for live fish transfer has been an important management strategy limiting the spread of VHSV in the region.

What it looks like

As the name describes, the virus can cause internal and external bleeding which in severe cases leads to organ failure and death. However, it is important to note that clinical lesions can vary among susceptible species. For example, walleye can develop severe hemorrhagic lesions, while muskellunge appear fairly normal despite being highly susceptible to low levels of virus.

Get involved

Fish kill events in Minnesota are widespread, and may provide clues about VHS and other ecosystem issues. Reporting these fish kill events is an easy and effective way to do your part to help protect Minnesota waters. The online, user-friendly database is available now at http://z.umn.edu/fishkill. It simply asks for the date, the location of the fish kill, and other basic information of any fish kill you observe. Once reported, fish kills are triaged and, if appropriate, trained biologists and students will collect samples to diagnose the cause of mortality. Do your part to protect our waters by reporting fish kill events that you see.

VHS research at MAISRC

Researchers  vhs

Completed efforts

  • Developed a new diagnostic assay that is 1,000 times more sensitive, lowered turn-around time from 28 days to 4 hours, and reduced cost by 40% compared to the previous test
  • Performed annual surveys since 2007 of high-priority state waters for early detection of VHSV
  • Created and offered training programs for veterinarians, aquaculture producers, and field biologists to effectively identify and respond to a VHSV outbreak
  • Developed science-based risk management recommendations that have been implemented by the Minnesota Department of Natural Resources to prevent the introduction and spread of VHSV

Current efforts

Since 2007, the University of Minnesota has been a leader in Viral Hemorrhagic Septicemia virus research and outreach efforts focused on early detection and prevention. The results from this work have better prepared Minnesota to rapidly respond and limit the spread of this potentially devastating disease. Current efforts have shifted gears to focus more broadly on fish health threats of emerging concern, including: novel pathogen discovery, investigation of fish kill events, and the pathways of infectious agent spread. These areas of research have broad impacts to understanding and managing other aquatic invasive species and overall health of the state's aquatic ecosystem.

Completed projects

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