Volume 4 2011

Anna Wilson, a UW-Madison graduate student, is working to develop and validate a test for VHS. Photo: Tony Goldberg.
Sea Grant Research

Researchers Are on the Hunt for Faster, Cheaper VHS Test 

By Moira Harrington

Wisconsin’s Little Lake Butte des Morts has the dubious distinction of being the site four years ago of the state’s first inland outbreak of viral hemorrhagic septicemia (VHS), a deadly fish disease. Going forward, the lake may become distinctive for a more positive reason. That’s because some Sea Grant-funded scientists are on the hunt for a faster, cheaper VHS test, and they’ve returned to that same area to puzzle it out.

“Our main goal is to develop an antibody test that lets us know whether the VHS virus was present in a fish population that won’t require any fish to be killed,” said Tony Goldberg, a UW–Madison Veterinary School epidemiologist and one of the principal investigators. “That’s especially important for valuable and large game fish like musky and walleye.”

VHS does not affect people or pets, but it can infect at least 25 species of fish and cause them to bleed to death. VHS has been detected in a variety of species in Wisconsin’s Lake Michigan waters and in lake herring from Wisconsin waters of Lake Superior. It doesn’t appear other inland waters have suffered from VHS, but concerns about future spread remain.

Goldberg and his fellow researchers have collaborated with Wisconsin Department of Natural Resources (WDNR) fish crews to collect blood and organs from freshwater drum. They want to learn whether the VHS virus is still active in Lake Winnebago and to understand when in a calendar year the virus poses the biggest threat to fish. Such predictive abilities could offer a new way to monitor and manage VHS throughout all of Wisconsin’s waters and would be of interest to resource managers around the Great Lakes basin, country and world.

The presence of antibodies in the drum indicates whether the fish were exposed to the virus, survived and subsequently developed an immune response. By sampling drum in early spring, before VHS typically emerges, and once in late spring, after the virus typically emerges, the researchers can track the infection status of Lake Winnebago drum over the transmission season each year. These new data, in combination with the WDNR’s long-term records of Lake Winnebago watershed drum, will be used to make statistical predictions about when and where VHS is most likely to occur in the future.

Goldberg suspects the infection may occur in waves, as new fish enter the fishery, or as the immunity wanes in older fish that survived the initial infection. “We think it could be like mumps in humans, with new waves starting as immunity wears off.”

Sue Marcquenski of the WDNR said the test is also expected to help yield more accurate results regarding the true distribution and prevalence of the virus. The current test can only detect the presence of the virus when it is active. The new test will detect antibodies to the virus, which means the fish were infected at some time in the past and survived the infection.

Anna Wilson, a UW–Madison graduate student, will develop and validate the VHS test as part of her master’s thesis in collaboration with Kathy Kurth at the Wisconsin Veterinary Diagnostic Laboratory, UW–Madison.

Kendall Kamke, senior WDNR fish biologist, noted that although there have been no obvious ongoing effects of VHS on the drum population or on other species in Lake Winnebago, the test will be a good tool. “There’s nothing I could point to and think it might be related to VHS,” he said. “But if they can give us a test that will allow us to avoid killing fish and something that could predict the threat level based on XYZ criteria, that would be the silver lining.”

The Aquatic Sciences Center is the administrative home of the
University of Wisconsin Sea Grant Institute & University of Wisconsin Water Resources Institute.

©2011 University of Wisconsin Board of Regents