VHS - Viral Hemorrhagic Septicemia
1. What is VHS and where is it from?
Viral Hemorrhagic Septicemia, known as VHS, is an infectious disease of fish that was first diagnosed in 2005 in fish in the Great Lakes, and was confirmed as the cause of fish kills in lakes Huron, St. Clair, Erie, and Ontario and the St. Lawrence River in 2005 and 2006. VHS was detected for the first time this spring in fish from Wisconsin waters of the Lake Winnebago System and Lake Michigan. Fish biologists believe the virus may soon be in fish from lake Superior and the Mississippi River and their tributaries if it's not already there.
Historically, VHS was known as a very serious disease of farm-raised rainbow trout in Europe. The Great Lakes strain of VHS is genetically different than the strains from Europe and the Pacific Northwest, in that the Great Lakes strain seems to affect a wider range of freshwater species over a broader range of water temperatures.
2. Is VHS a health risk for people?
No, VHS is not a health risk for people so anglers can continue to enjoy fishing and eating their catch. VHS has never been associated with human illness since first being discovered in European fish decades ago (DHFS< May 2007). Fish can be infected by VHS, but may not show signs of disease. Such fish are safe to eat so long sas the fish is properly cooked. Generally, however, you should not eat fish you find dead, decomposing, or that appear sick, regardless of cause. Such decomposing fish may attract other bacteria harmful to people.
3. Why do fish biologists consider VHS a serious threat to Wisconsin fish?
Fish biologists consider the virus a serious threat to Wisconsin fish for several resons: it can spread easily between fish of all ages, it affects a broad range of our native game fish, panfish and bait fish, as well as "rough" fish, and it often kills fish. The strain that has shown up in the Great Lakes is new and fish here have had no exposure to the virus, meaning their immune systems have no defense and are "highly susceptible." This is the first time a virus has affected so many different fish species from so many fish families in the Great Lakes.
4. How did VHS get into our lakes?
VHS virus is considered an invasive species (not native to the Great Lakes), but scientists are not sure how the virus arrived. The disease has been found in three inland lakes, one each in New York, Michigan and Wisconsin, and could have hitchhiked in a live well, bilge water, on a boat or in minnows or other live fish.
5. How does VHS spread in a fish population and to new lakes?
Infected fish shed the virus into a lake or river through their urine and reproductive fluids. VHS virus can remain infective up to 14 days in water. The virus is absorbed into the gills of healthy fish. Healthy fish can also be infected when they eat an infected fish. Infected fish and water can easily spread the virus if they are released into a new water body. That's why new emergency rules prohibit anglers, boaters and other water users from moving live fish ans water from one waterbody to another.
6. What are the symptoms of a fish infected with VHS?
Like many fish diseases, the type of symptoms present in a fish change with the severity of the infection. Fish may display few to no symptoms, or as the infection worsens, signs may include bulging eyes, bloated abdomens, inactive or overactive behavior, bleeding in the eyes, skin, gills and at the base of the fins. Because many of these signs look like those caused by other fish diseases, testing is necessary to determine whether a fish is infected with VHS.
7. What is the long-term outlook for VHS in the Great Lakes and state fish population?
It's hard to say right now because the fish virus is new to the Great Lakes region, and unlike strains in other parts of the world, seems to be affecting a broader range of fish. Fish that survive the infection will develop antibodies to the virus. Antibodies will protect the fish against new VHS virus infections for some time. However, the concentration of antibodies in the fish will drop over time and the fish may start shedding the virus again, creating a cycle of fish kills that occur on a regular basis. On the other hand, experiences from other Great Lakes indicate that fisheries can and have bounced back.
8. Are there any rules related to VHS that I need to be aware of as an angler or boater?
Yes. The state Natural Resources Board ahs adopted emergency rules that prohibit angers, boaters and other recreational users from moving live fish, including bait minnows, ans water from the Lake Winnebago watershed, Great Lakes, Mississippi River, and those waters' tributaries up to the first dam impassable by fish. The rules also require that people fishing in those waters use minnows purchased only from Wisconsin licensed dealers, or, if harvesting their own minnows, that the bait is used only on the water in which it was caught.
9. What can I do to help prevent the spread of VHS?
The DNR is asking the public to take precautions similar to those used in stopping the spread of invasive species:
Put your catch on ice and do not move live fish (including unused bait minnows) away from the landing or shore;
Drain all water from bilges, bait buckets, live wells and other containers when leaving the landing or shore;
Use live minnows purchased only from registered bait dealers in Wiscdonsin or catch it yourself in the same water you fish; and
Before launching and before leaving for the day, inspect and clean all watercraft for visible plants and animals.
10. What should I do if I see a fish kill or diseased fish?
Note the waterbody, date, fish species, and approximate number of dead/dying fish.
If you caught a suspicious looking fish, place the fish in a plastic bag and then in a cooler on ice.
Contact either your local fisheries biologist or call the DNR TIP line (1-800-TIP-WDNR (1-800-847-9367) - Click here for more information