The Great Lakes Fishery Trust has announced a $750,000 grant to address viral hemorrhagic septicemia (VHS), a lethal viral disease affecting fish.
Researchers from the U.S. Geological Survey, Michigan State University, Cornell University, and Western Fisheries Research Center have joined forces in order to provide resource managers in the Great Lakes region with new tools and information. Regional managers will then be able to utilize this information to better understand, predict, and manage the threat posed by this deadly disease.
First Regional Identification of VHS
The earliest confirmed report of VHS disease was in muskellunge in Lake St. Clair. Scientists surmise that disease introduction took place in 2002 or 2003, though they are not sure how long the virus has actually been in the lakes.
VHS Symptoms
Sick fish often appear listless, swim in circles, or hang just below the surface.
Fish infected with VHS often exhibit hemorrhaging in the skin - large, red hemorraghic patches can be found on the sides and anterior portion of the head. Yet sometimes infected fish exhibit very minor external hemorrhaging, or none at all.
Many internal organs are often congested with multiple hemorrhages.
The ultimate cause of death is usually internal organ failure.
Humans not Affected by Virus
VHS is not a human pathogen. It cannot replicate in warm-blooded animals, so humans will not become infected if they eat fish with the pathogen.
The Spread of VHS
The virus is widely distributed in Lakes St. Clair and Erie, and scientists believe that the virus will be found throughout lakes Huron and Michigan in the next 2-4 years. This hypothesis is based on the large scale fish movements, particularly Chinook salmon, between lakes Michigan and Huron. Also, long distance movement within each lake by Chinook and coho salmon along with walleye and other prey species affect virus distribution.
The virus will probably take a long time to get established in Lake Superior, because fish movement through the Soo Locks is limited. However, the situation could rapidly change if ballast water exchange becomes the key vector in virus transmission.
Duluth Harbor in Western Lake Superior has the second highest ballast water exchange rate in the Great Lakes. Chicago also has a very high ballast exchange rate. If the virus can remain alive for sufficient time in the ballast water of boats, it could quickly be transported by this method.
Although it is not known exactly how this virus arrived in the Great Lakes, ballast water discharge is considered the most likely cause given its distribution in the Great Lakes region and the likely origin of the virus, the Maritime Provinces of Canada.
The United States Department of Agriculture – Animal and Plant Health Inspection Service (USDA-APHIS) has issued emergency orders that restrict fish movement over state and national boundaries. Find the most recent order on their website.
Reference
Whelan, Gary E. Viral Hemorrahagic Septicemia (VHS) Briefing Paper. August 1, 2007
