Fish virus has not spread to area lakes: Virus affects mostly bass but is no threat to humans

By Matt Bewley… Fergus Falls, Minnesota…. Wednesday, January 03, 2007                                           

A fish disease discovered five years ago in the Mississippi River has spread to Minnesota's inland lakes, though it doesn’t present a danger to humans, the Department of Natural Resources announced in December.

Largemouth Bass Virus is an iridovirus virus, or one that only affects fish, amphibians and reptiles. It has been found in 20 states since its discovery in 1991. Last summer, the disease was found in five of nine metro area lakes sampled.

“As far as we know, it’s not present here,” Area Fisheries Supervisor Arlin Schalekamp said, “though I don’t think the fish have been sampled for it, here. I suspect that over the next year or two years, we’ll see sampling over the state, but I don’t know where that sampling will start.”

Cooked or raw, eating the fish with the virus itself is not dangerous to humans, he said.

“The virus can’t spread to humans,” Schalekamp said. “But we strongly suggest people do not eat raw largemouth. There are a lot of parasites in largemouth bass that may be transferred, including tapeworms, and some of those are really nasty creatures.”

“We need to keep a sharp eye on the presence and impacts of Largemouth Bass Virus,” DNR fisheries program consultant Al Stevens said. “The virus has been documented to cause high mortality rates of bass caught and released in tournaments conducted in hot weather.”

“Over the past several years,” Schalekamp said, “there have been cases of it in the eastern and southern states. They’re found it in those populations. How they got there is open to speculation, though they have been present for some time, and it is gradually working it’s way north and west.”

The DNR is considering rules that could ban off-site weigh-ins at bass fishing tournaments during the hottest times of summer.

“We’ll have to revisit the whole tournament catch-and-release format,” he said. “We don’t want, and (the tournament organizers) don’t want to see a lot of fish die. I know that the southern states are dealing with this right now, trying to come to terms with this. Some are considering immediate catch-and-release.”

This format requires that the fish be returned to the water after a digital picture of the fish on a measuring board is taken, meaning that the longest fish, not the heaviest, would win the event.

Found primarily in the southeastern United States, the disease is known to occasionally cause fish kills, generally in relation to stress from high water temperatures and from handling and transportation by anglers. The disease may spread by either transporting fish or water from infected lakes.

“Anglers should always drain their live wells when leaving lakes,” Stevens said. “By taking this action, we can slow the spread of diseases like LMBV as well a number of other invasive species such as zebra mussels and Eurasian watermilfoil.”

The DNR partnered with the Minnesota Bass Federation to collect samples following bass fishing tournaments at nine metro area lakes known to receive high fishing pressure. The disease was discovered at Green Lake (Chisago County), Prior Lake, Lake Minnetonka, Rush Lake and Forest Lake. Lakes sampled that were negative for LMBV are Clearwater Lake, North/South Center Lake, Whitefish Lake and Green Lake (Kandiyohi County).

So far, the disease has proved fatal only in largemouth bass. The virus attacks the swim bladder and may cause largemouth bass to appear bloated. The disease also affects their ability to control their buoyancy and maintain their position in the water.

Other members of the sunfish family known to become infected with the virus include spotted bass, Suwanee bass, smallmouth bass, bluegill, redbreast sunfish, white crappie and black crappie.

For more information, call the Department of Natural Resources at 218-739-7576.