National Aquatic Health Program - FAQ's
Viral Haemorrhagic Septicaemia (VHS) in various Great Lakes fish species
There have been reports of wild fish mortalities associated with the emergence of VHS in various freshwater fish species in the Great Lakes. Until 2005, VHS was believed to be limited to natural infections of marine fish species on the Atlantic and Pacific coasts of North America.
In 2005, mortalities appeared in the Bay of Quinte, Lake Ontario and Lake St. Clair. In 2006, VHS has been detected in an increasing number of freshwater fish in Lake Erie, in both Canadian and American waters. A fact sheet and frequently asked questions have been prepared to provide basic information about VHS to recreational anglers, commercial fishers and fish farmers to increase awareness and convey basic precautionary measures.
Frequently Asked Questions
What is Viral Hemorrhagic Septicemia VHS)?
- VHS is an infectious disease caused by the viral haemorrhagic septicemia virus.
- There are several known strains of VHS that effect freshwater and marine fish around the world. In North America, VHS strains are found in the marine and estuarine waters of the Pacific and Atlantic.
- Fisheries and Oceans Canada (DFO) has determined that the VHS virus detected in the Great Lakes is a North American strain, and most closely related to the strain found on the east coast.
- The occurrence of VHS in the Great Lakes is the first time that it has been detected in a freshwater in Canada.
Is VHS dangerous for people handling or consuming Great Lakes fish?
- VHS, like most other diseases that affect fish health, has no impact on human health. Fish can be infected by VHS, but still be perfectly healthy. Such fish are safe to eat.
- It is safe to handle VHS infected fish even if they are dying or dead.
- However, no-one should consume dead or sick fish, regardless of cause.
What fish are affected by VHS in the Great Lakes?
- In Canada, freshwater drum; smallmouth bass; crappie; muskellunge; and bluegill have been affected by VHS.
- In the United States, VHS has been detected in round goby, muskellunge, gizzard shad, walleye, white bass, silver redhorse, northern pike, freshwater drum, yellow perch, smallmouth bass, and shorthead redhorse.
Where did the virus come from and how?
- The virus infecting both sick and apparently healthy fish in the Great Lakes appears to be the same. It is closely related to the VHS strain detected in marine fish within Atlantic and eastern Gulf of St. Lawrence waters.
- How VHS spread to the Great Lakes is unknown. The wide number of species affected and detection in both healthy and infected fish means that it could have spread from Atlantic Canada or be widespread, but only causing mortalities when water conditions are conducive.
- Samples held in storage since 2003 indicate the virus may have been present in the Great Lakes since then. Archived samples require more analysis to define the actual date of appearance of VHS in the Great Lakes.
How do fish become infected and how does the disease spread?
- We don't know the exact pathway of VHS infection. Under laboratory conditions, the virus is shed by infected fish and acquired by neighbouring fish.
- Fish that have been exposed to and survived the infection directly or via their parents are able to fight the disease, but may still carry the virus.
What does a fish infected with VHS look like?
- bulging eyes
- pale gills
- signs of bleeding around the eyes, bases of the fins, sides and head
- darkening overall colour
- distended (fluid-filled) belly
- corkscrew swimming behaviour
Photograph courtesy of Dr. J. Lumsden, University of Guelph
What is the Government doing to control VHS effects and spread?
- Fisheries and Oceans Canada and the Canadian Food Inspection Agency are working closely with the provinces as well as with the Canada-USA Great Lakes Fish Health Committee to assess the extent of the infection and the disease.
- Workshops to assess knowledge on Great Lakes VHS detections to date are being held to share information, identify knowledge gaps that require immediate research and discuss management options.
What should I do if I find a sick or dying fish?
Never return fish with obvious signs of disease to the water. If you are concerned that a fish is showing obvious signs of disease, contact your local fisheries authority.
What activities are affected by the emergence of VHS in the Great Lakes?
Anyone wishing to move live fish from one part of the Great Lakes to another (especially from areas noted as being positive for VHS) should contact their local fisheries authority or DFO.
Where can I get more information?
- DFO - National Aquatic Animal Health Registry;
- CFIA - National Aquatic Animal Health Division;
- Date Modified: