Prevention, the only defense for VHS, the latest disease attacking fish

VHS, or viral hemorrhagic septicemia in its long form, is, as its name implies, a virus that attacks freshwater and saltwater fish with apparent impunity. Common in trout hatcheries in Europe and suspected to cause die-offs of Pacific salmon in the Northwest, the disease appeared in 2006 in the Great Lakes in a form not before seen.

It hasn’t been found in Colorado nor any of the adjacent states, but if it’s anything like zebra snails, which recently were found in Pueblo Reservoir, the disease likely can travel faster than prevention can stop it.

And being a virus, the only treatment is prevention, said state fisheries manager Greg Gerlich in a presentation last month to the Colorado Wildlife Commission.

It’s on the radar, he said, meaning the state and Colorado’s private aquaculture industry is doing everything possible to prevent the disease from entering the state.

Google viral hemorrhagic septicemia and you’ll get more than 42,000 hits, a sure sign that someone somewhere is interested in the disease’s progression.

According to the U.S. Department of Agriculture, an apparently new strain of VHS in the Great Lakes region has caused reported die-offs in muskellunge, smallmouth bass, northern pike, freshwater drum, gizzard shad, yellow perch, black crappie, blue-gill, rock bass, white bass, redhorse sucker, bluntnose sucker, round goby and walleye.

There is no evidence for how the virus reached the Great Lakes, said the USDA report, nor how long the disease was present before being noticed.

Wisconsin and Michigan have adopted restrictions on fish movement and transport.

The Great Lakes virus also can kill all trout species, including the fragile populations of Colorado River and greenback trout Colorado has labored so hard to preserve.

The disease also was found in upstate New York, where researchers from Cornell University reported large-scale fish die-offs in goby, a small fish that serves as an important prey species for commercially valuable fish. Cornell researchers are attempting to produce a rapid diagnostic test for the disease.

As DOW fish pathologists Carolyn Gunn and Pete Walker wrote on the Web site of the Colorado Aquaculture Association, “There is much that is unknown about the spread of this disease, and researchers are scrambling to stay ahead of this pathogen. As with most viral diseases of fishes, treatments are not available, so prevention is the only defense.”

Colorado’s private hatcheries already are testing for a multitude of diseases, said Greg Brunjak of the Colorado Fish Health.

“We haven’t been testing for VHS because it was thought to be a European disease,” he said. “But with the findings in the Great Lake, you can be sure we’ll be watching for it.”

With the state and private hatcheries now aware of the disease, the biggest concern is unknowing transport of the virus by anglers or by unscrupulous bait dealers who go into a VHS-positive state, net bait fish and bring those fish and the virus into Colorado.

“It’s the rogue dealers we’re worried about,” said Gerlich. “This can be a bad deal for Colorado.”

Private facilities already have to follow strict regulations from the Colorado Department of Agriculture and bait dealers, too, must have a state permit. Often, however, small bait operations, which might be one person selling bait from the back of truck at some warm-water reservoir in southeastern Colorado, do not have a permit.

“It can be cost prohibitive to have a $300 permit so some dealers might not worry about it, figuring they’ll never get checked,” Gerlich said. “But we don’t know where those people get their fish, and those are ones who might bring VHS into Colorado.”

Communities in English

Communities in Spanish

Communities in Portuguese

Prevention, the only defense for VHS, the latest disease attacking fish