Wisconsin DNR Reacts To Viral Hemorrhagic Septicemia

Press Release Posted 5/22/07

MADISON - The Department of Natural Resources announced Saturday that two fish from Little Lake Butte des Morts in the Lake Winnebago chain of lakes have preliminarily tested positive for the deadly fish virus called viral hemorrhagic septicemia or (VHS). Additional dead fish samples taken from Lake Winnebago, itself, appear to have the virus.


Though VHS is not a health threat for people who eat or handle fish infected with the virus, it can infect more than 25 game fish, panfish and bait fish species. State fish managers had suspected it to be present in Lake Michigan and possibly in Lake Superior and in the Mississippi River. This would be the first infection to be confirmed in Wisconsin inland waters. Wisconsin recently enacted emergency rules for boaters, anglers and people who harvest wild bait to prevent the spread of VHS in inland waters


"This is a major fish health crisis," said Fisheries Director Mike Staggs, "We have to take aggressive steps now and enlist the help of the public to stop this spread."


Fish managers met Saturday to implement immediate steps to deal with the infection and limit its spread. DNR asked the Fox Locks Authority to close the Menasha Lock immediately and to keep it closed until more information about the spread of the disease could be confirmed; boaters can expect to be turned back from the lock starting today. In addition, DNR began the process of posting all boat launches with actions boaters should take to avoid spreading the disease.


"We need to err on every possible side of caution," Staggs said. "Believe me, nobody wants to see this disease get into more of our lakes. Do not take 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."

Little Lake Butte des Morts is downstream from Lake Winnebago and separated by one dam and one functioning lock, which has now been closed. The Lake Winnebago chain is home to Wisconsin's unique sturgeon population. On May 11, 2007 the University of Wisconsin Veterinary Diagnostic Lab (WVDL) informed DNR that two samples of freshwater drum taken from Little Lake Butte des Morts on May 2, 2007 had tested positive for VHS. The samples have been sent to an approved federal lab for confirmation.


The fish were collected by DNR fisheries staff during muskellunge spawning netting and were submitted for testing because they had shown external signs of VHS. Since that time, DNR has been receiving reports of hundreds of freshwater drum dying on Lake Winnebago, itself. On May 9 and 10 samples of those dead fish were sent to WVDL for testing. A visual inspection of the Lake Winnebago fish by DNR's certified fish health inspector showed the same external signs of VHS as the Little Lake Butte des Morts fish. Also the DNR staff that collected the fish on Little Lake Butte des Morts reported seeing dead and dying drum washing over the dam separating that water from Lake Winnebago.


Because the virus can infect so many different ages and species of fish, VHS could spread more quickly in inland lakes, which are much smaller than the Great Lakes, potentially devastating fish populations and fishing opportunities. Walleye, spotted musky, yellow perch, bluegill and northern pike are all susceptible to the virus, as are common bait species such as emerald and spot-tail shiners.
DNR is appealing to anglers, boaters and other water users to help prevent the further spread of VHS by taking a few simple steps:


· Never move live fish or fish eggs to other waters and always buy bait minnows only from Wisconsin bait dealers because bait from other states may not have been tested for VHS. These steps are required by the new emergency rules.

· Inspect boat, trailer and equipment and remove visible aquatic plants, animals, and mud before leaving the lake launch.

· Drain water from boat, motor, bilge, live wells, and bait containers before leaving a lake. This step is recommended for boaters on all waters and is required under the emergency rules for boaters on the Great Lakes and the Mississippi River and their tributaries up to the first dam.

· Dispose of leftover bait in the trash, not in the water. Do not take live fish or live fish eggs away from the boat landing.

· Rinse boat and recreational equipment with hot water OR dry for at least five days.

· Report large numbers of dead fish or fish with bloody spots to your local DNR fish biologist or conservation warden.

Wisconsin already has taken steps to deal with VHS. The state Natural Resources Board on Wednesday, April 4, unanimously passed emergency rules prohibiting anglers and boaters from moving live fish, and requiring them to drain their boats and livewells, before leaving Wisconsin's Great Lakes waters, the Mississippi River and those waters' tributaries up to the first dam.
Fishing in Wisconsin is a $2.3 billion industry. More information on aquatic invasive species and Wisconsin's programs to prevent their spread is available on the DNR Web site.

Important Questions and Answers on Viral Hemorrhagic Septicemia (VHS)

What is VHS? What is the significance of the recent discovery of VHS in the Great Lakes?
Viral Hemorrhagic Septicemia is an infectious viral disease of fish that has been found in fish from the Atlantic Coast of Europe and Atlantic and Pacific Coasts of North America. Historically, VHS was known as a very serious disease of freshwater-reared rainbow trout in Europe. At least four different genetic strains or forms of the virus are known to exist. The North American marine strain has a relatively low infection rate compared to that of the European freshwater strain. Until 2005, VHS was only found in the marine environment in North America. Several fish kills in the Lower Great Lakes since 2005 have been associated with VHS. To date, VHS has been confirmed from wild fish in the Bay of Quinte Lake Ontario, Lake St. Clair, Lake Erie and the St. Lawrence River. Scientists believe that this appearance may represent an invasion of the freshwater strain in North America.

What North American freshwater fish species are affected?
In the Great Lakes, VHS has been found in smallmouth bass, yellow perch, crappie, muskellunge, northern pike, bluegill, walleye, round gobies, sheepshead, and some sucker species. Scientists are concerned; however, that VHS could also strike native salmonids such as trout, salmon and whitefish in the wild, and salmonids in hatcheries and net pen operations.

How did VHS get here?
It is unclear how the virus spread to the Great Lakes; it is possible the marine virus may have been introduced to the Great Lakes some time ago and it simply evolved to live in freshwater. The VHS virus is a strain that undergoes rapid mutations (spontaneous genetic changes) and may have adapted to freshwater environments in North America. Recently, VHS was found in stored fish samples that were collected in the Great Lakes during 2003, suggesting the virus has been present in the Great Lakes for some time.

How does VHS spread?
It is unclear exactly how the disease is spread but it appears that the virus can be shed by infected fish into the water through metabolic waste materials, particularly by fish that survive the disease and become carriers. It also appears that carrier fish or offspring of carriers become more resistant to the disease. The virus can infect fish of all ages. It may enter a host fish through the gills or food or contact with some contaminated object. It does appear that stressed fish more vulnerable to viral infection. Typical fish stressors include sudden water temperature changes, crowded hatchery conditions and, spawning activity. The timing of the recent fish die-off in the Great Lakes coincided with the spawning by some of the fish species, such as muskellunge.

What does it do to fish? What are the symptoms of a fish with VHS infection?
Like many fish diseases, the type of symptoms present in a fish change with the severity of the infection. At low infection intensity fish may display few to no symptoms as is the case in most wild disease outbreaks. Hatchery or pen-reared fish are much more susceptible because of the confined conditions. As the infection severity increases, fish become darker and the eyes bulge with some bleeding around the eye and base of the fins. The gills are usually quite pale with some pin point bleeding. Mortalities appear at this point because hemorrhaging reduces the oxygen carrying ability of the blood. Dark red patches may appear on the front and sides of the head.

If the fish is opened up, bleeding on the surfaces of the intestine, liver, swim bladder can be seen. Fluid also builds up in the body cavity giving the fish a swollen belly. Later, if infection increases, the body continues to darken and the eyes really stick out of the head. At this point, the gills look gray or even white and the fish may swim in a corkscrew pattern. Most fish kills from VHS occur in water temperatures from 40 to 60 F (3-12 C) and few occur at temperatures above 62 F (15 C). NOTE: The detection of a VHS infection can only be made from sophisticated laboratory testing. A diagnosis cannot be made based solely on the observation of visible signs because many different diseases of fish have very similar signs of disease.

What is the long-term outlook for VHVS in the Great Lakes?
Diseases like VHS run their course just as they do in human populations. At first mortalities may appear to be large, but many biologists believe that most fish can survive the disease if they are not otherwise stressed because mortalities generally occur in weaker, stressed fish. The remainder will build up a natural immunity to the virus and the numbers of fish killed by the virus will decline.

Is it a health risk to people?
There is no apparent health risk for people contracting VHS. Because it takes a long time to identify the causes of fish kills in lab studies, people should be cautioned against handling or eating any fish that does not act or appear to be healthy because of the risk of contracting avian botulism a bacterial disease that does pose a human health threat.

What is being done to prevent the spread of VHS?
The state Natural Resources Board passed Emergency Rules effective April 2007 require that boaters and anglers:
Note: In light of a preliminary positive test of two fish on Little Lake Butte des Morts, the DNR is asking all boaters and anglers to immediately adopt these practices on all state waters.
· Drain all water from your boat, trailer, bait buckets, coolers, and other containers before you leave the landing or shore fishing site location on Lake Michigan, Lake Superior, the Mississippi River or their tributaries).
· Do not transport live fish, including bait fish, away from any Great Lakes or Mississippi River drainage landing or shore fishing location. This includes tributaries up to the first dam.
· Do not use "cut" or dead bait from other waters (except when fishing in Lake Michigan, Green Bay, or tributaries).
· Do not use minnows unless they were purchased from a Wisconsin bait dealer or you legally caught the minnows from the place you are fishing.
In a hatchery, the best means of controlling the disease is to prevent the contact of the virus and fish. This can be done by hatchery disinfection, egg treatment with anti-viral agents, and using ultra-violet light treatment of hatchery water. It is important to stock disease free fish and to monitor freshwater populations for signs of further spread. Information on diseased wild fish is difficult to obtain because they often die undetected and fish can decompose rapidly making disease diagnoses very difficult. New research is being developed that would allow more rapid detection of the disease.

What should I do if I see a fish kill?
If you observe a fish kill on the Great Lakes, please contact the Wisconsin Department of Natural Resources at (608) 266-8782 or your local DNR office. If you see fish with any of the outward signs of VHS as described above please mention this as well. This will help biologists keep track of where the disease may be appearing.

These questions and answers about VHS were developed by the University of Wisconsin Sea Grant Institute and the Department of Natural Resources

©Copyright 2007. Donald Lee Jordan