AUSTIN, Texas -- A virus responsible for killing largemouth bass on four popular Texas reservoirs in the summer of 1999 and linked to almost 20 die-offs nationwide is not currently killing fish in Texas, according to Texas Parks and Wildlife officials.

A recent TPW study showing that the virus is present in two-thirds of the state's watersheds has raised concerns that bass may still be dying from largemouth bass virus (LMBV) in Texas lakes.

"We want to reassure Texas anglers that while we are concerned about largemouth bass virus and will continue to monitor the situation there are no bass virus fish kills occurring now and the virus is not a reason to cancel any fishing trip you've planned," said Phil Durocher, TPW inland fisheries director. "We have not had a die-off associated with the virus since the summer of 1999."

Durocher said that although some of the fish in Texas are carrying the virus, the fish are in good shape, and fishing is excellent in most lakes. He added that the presence of the virus poses no threat to human health if fish are consumed.

"What we now know is that this virus is not always a problem, not always lethal to fish," said Dave Terre, TPW regional fisheries director in Tyler and Texas' representative on a multi-state team of researchers investigating the virus. "It's just out there in the environment, and when conditions get right, we may have some fish die. It may be so minor that it's not noticeable, but when it impacts a fishery like Lake Fork or Sam Rayburn, it gets noticed."

TPW investigated 49 lakes in 2000 to determine the presence of LMBV. Scientists at the A.E. Wood State Fish Hatchery in San Marcos confirmed the virus in samples from 14 of the lakes. The infected bass populations reside in nine of 14 major river basins tested statewide. Only a small segment of the overall fish population in those water bodies -- 5 percent on average -- tested positive for the illness, and none of the affected fish appeared to be stressed or dying.

Listed below are lakes in which the virus has been detected. No known fish kills are now occurring in any Texas lakes. In East Texas, the virus has been detected in the following river drainages: Red River (Lake Texoma) Cypress (Lake Cypress Springs) Sabine (Lake Tawakoni, Lake Fork, Toledo Bend Reservoir) Neches (Lake Athens, Lake Palestine, Lake Tyler, Lake Nacogdoches, Sam Rayburn Reservoir) Trinity (Lake Bridgeport, Lake Livingston) The virus also occurs in Central Texas and affects the following river systems: Brazos (Hubbard Creek Reservoir, Lake Possum Kingdom, Lake Whitney, Lake Belton) Colorado (Lake Buchanan) Guadalupe (Canyon Lake) San Jacinto (Lake Conroe) Major river basins that tested negative for LMBV include the Arkansas (Canadian), San Antonio, Nueces, Rio Grande and the Sulphur.

The TPW findings illustrate the distribution and density levels of the virus in Texas, but researchers admit little else is known about LMBV. "We've completed the lab analyses of fish collected and wanted to make sure the angling community is aware of where we are at this point," said Terre. "This is not the end, just a chapter. There are a lot of variables we collected along with the fish that will take some time to analyze."

According to Auburn University scientist John Grizzle, LMBV is one of more than 100 naturally occurring viruses that affect fish but not warm-blooded animals. Its origin is unknown, but it is related to a virus found in frogs and other amphibians and almost identical to a virus isolated in fish imported to the United States for the aquarium trade.

Although the virus apparently can be carried by other fish species, to date it has produced small numbers of deaths only in largemouth bass. Researchers have discovered that LMBV can stay alive in water for at least three to four hours. "Tentatively, that means you could transport the virus in a livewell, bait bucket or in bilges," Terre said. "We also now know that bass can contract the virus from contact with other fish, but we still do not know how the virus is activated into a fatal disease and if there is a cure or a preventative."

LMBV first gained attention in 1995, when it was implicated in a fish kill on Santee-Cooper Reservoir in South Carolina. Since then, the virus has been found in water impoundments throughout the South and during 2000 was confirmed as the source of a kill in Lake George on the Indiana-Michigan border. The virus has been detected in bass that show no signs of illness, which suggests that some fish might be infected but not ever become sick.

Biologists are uncertain about how long the virus has been present in Texas waters, but the pattern suggests that unusually hot summer temperatures were a catalyst in the die-offs. According to lab analysis conducted in the summer of 1999, bass samples from Lakes Conroe and Toledo Bend tested positive for the LMBV in addition to those from Lake Fork and Sam Rayburn.

"The year the virus impacted Lake Fork, over half the bass sampled tested positive," said Terre. "That didn't mean 50 percent were dying, just that they carried LMBV. When we came back and tested again last year, only 3 percent of the Lake Fork bass we tested carried the illness. We don't understand the mechanics by which it becomes prevalent, but it seems to happen just once in varying levels, and outbreaks do not repeat."

The good news, he noted, is that there has never been a fishery lost because of LMBV. "The only significant thing we've been able to determine is that when the virus occurs, angler catch rates, particularly for large fish, decline for a short period of time and then recover."

Because the virus appears to strike a fishery and move on, researchers say finding answers to its mysteries may take years, and even if uncovered may be a moot point. "Who's to say this will even be a problem in 10 years or even if it'll be around?" asked Terre. "We need to be taking a look at fisheries in areas where the virus hasn't hit, like California and Canada, to determine if and where it already exists. This is a national problem that's getting more interest as more states are impacted."

TPW has taken a leadership role in looking for answers with it's A.E. Wood facility now geared up to accommodate lab analysis specific to LMBV, but Texas is not alone. "We obtained the equipment and expertise to test for LMBV," said Terre. "Also, we continued our investigation into hatcheries and into the kills on Fork and Rayburn.

In addition to TPW, leaders in LMBV research include the federal Warm Springs, Ga., Fish Health Center; Mississippi State University; Louisiana State University and Auburn University. Sport fishermen have also taken an active role, with the Bass Anglers Sportsman Society hosting to two LMBV summits, where researchers from various states affected by the virus shared information.

"Bass are No. 1 in Texas, and other states look to us for leadership in bass management," Terre said. "They also look to us for leadership in studying the virus -- and we're doing it."