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Focus on Exotics: VHS
What’s Lurking in Your Lake?
This edition’s “Focus on Exotics” highlights a very serious fish-killing disease known as Viral Hemorrhagic Septicemia or VHS. When you think about the term “invasive species,” you may think of plants, such as Eurasian Watermilfoil, or animals, such as the Asian Carp. What we may not be quick to identify as an invasive species are viruses. Yes, that’s right – viruses! Being true to its name, Viral Hem-orrhagic Septicemia, is indeed a virus – and an invasive species.
One property of a virus is that it needs a host to repli-cate. This particular virus uses fish as their host organ-ism to perpetuate its existence. Although VHS does not pose a threat to human health, it is deadly to fish and eas-ily transferable between many fish species of all ages.
VHS has been dated back to the 1930’s to European trout farms, where it continues to pose a threat to fish populations. This disease was first reported in the U.S. in 1988 where it appeared on the West coast. Identified in the Great Lakes region in 2005, VHS has been found in fish in both Wisconsin and Illinois as recently as June of 2008 and continues to spread throughout the region.
In July 2008, the Illinois Department of Natural Re-sources (IDNR) issued a statement for emergency regula-tions to stop the spread of this fish virus. You can read this press release which includes a list of fish species that are susceptible to the virus, as well as, how these regula-tions affect aquaculture or you as an angler or recrea-tional boater at: http://dnr.state.il.us/pubaffairs/2008/July/vhsvirus.html. These emer-gency regulations include:
Eliminating natural water from all equipment when leaving a body of water.
Emptying and draining all bait buckets, livewells, baitwells, bilges, etc. or any other compartment capable of holding natural waters when leaving a body of water.
Do not remove live VHS-susceptible species (see website) from any waters. Anglers may catch and keep VHS-susceptible species, but may not trans-port those fish live from the waters where caught.
Use of wild-trapped fishes from within the state as bait will be restricted to the waters where le-gally captured.
How can you identify a fish infected by VHS? The symptoms exhibited by fish with VHS can be very similar to other fish diseases. Therefore, it is important that VHS
be confirmed through labo-ratory tests. It is also impor-tant to know that some fish do not exhibit any symptoms of having the disease and are carriers of the disease. These fish may be unknow-ingly transported to other waters which will spread the disease. Some external signs of VHS are bulging eyes, hemorrhaging, abnormal behavior, bloated abdo-mens or rapid onset of death. If you catch a dis-eased fish or witness a fish kill, contact IDNR immedi-ately. For a fish kill, note the waterbody, date, fish species and approximate number of fish killed. If you catch a diseased fish, do not throw it back. Place the fish in a plastic bag and store in a cooler on ice.
How is VHS transmitted? Fish infected with the dis-ease can shed the virus through their urine and re-productive fluids. The virus can survive in the water for at least 14 days and is thought to enter the body through gills or an open wound. The gill tissue will be infected first followed by internal organs and blood vessels. The blood vessels be-come weak, which causes hemorrhaging of the internal organs, muscle and skin, resulting in the fish bleeding to death. The virus can also be transferred when fish eat infected fish or through the use of infected bait fish.
Viral Hemorrhagic Septicemia is a highly contagious aquatic disease. Because Great Lakes waters enter the Illinois River through the Chicago Sanitary and Ship ca-nal, your cooperation as an angler, boater or aquaculture professional is essential to help slow the spread of this disease to other Illinois waters and states downstream. To help prevent the spread of this disease, follow all regu-lations associated with VHS and remember to thoroughly clean your boat, trailer, nets and equipment used when traveling between different lakes and streams. This is a good practice to help prevent the spread of all aquatic invasive species.
Photo courtesy of South Dakota Game, Fish and Parks
Photo courtesy of Aquatic Animal Health Program, Cornell University
Photo courtesy of Wisconsin De-partment of Natural Resources
