LARGEMOUTH BASS VIRUS - USA: (VIRGINIA)
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A ProMED-mail post
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International Society for Infectious Disease <http://www.isid.org>
Date: 29 Oct 2010
Source: Richmond Times Dispatch (Virgina) <http://www2.timesdispatch.com/sports/sport/2010/oct/29/andy29-ar-614309/>
Officials looking into Briery Creek die-off
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The reports from readers came in around late June 2010: Fish are dying in Briery Creek Lake. "Have you heard anything about this?" was a common theme of their e-mails.
Word spread fast and theories were tossed about -- not surprising considering the lake's status as Virginia's premier impoundment for lunker bass. Now we know what likely was behind the die-offs: a combination of intense heat and, more ominously, a disease known as largemouth bass virus (LMBV).
According to a press release from the Department of Game and Inland Fisheries (DGIF), largemouth bass virus is a disease that impacts several fish species but appears to cause death only in largemouth bass. LMBV was 1st discovered in Florida in 1991, and then spread throughout the southern United States and was responsible for a number of fish kills in the late 1990s and early 2000s.
"The virus is the kind of thing that may be lurking all the time,"
said DGIF fisheries biologist Dan Michaelson, "but when you have an environmental stress like the hot temperatures . . . [the fish] just become more susceptible when they're stressed." Michaelson emphasized that the number of deaths in Briery wasn't huge, and the fishing hasn't suffered noticeably, but, he added, there's no way to tell if it will in the future. Given the lake's popularity, he said, "It's something we're going to keep a very close eye on."
The hope in Prince Edward County is that Briery Creek Lake escapes the fate currently befalling Kerr Reservoir (Buggs Island Lake) to the south. LMBV also has been found there and in much greater numbers, leading to a significant decline in the fishery.
"We actually were approached by anglers last winter saying they were starting to see a decline," Michaelson said. "And the way they described it -- not catching as many 3-4 pound fish, taking longer to catch those fish -- it immediately sounded to us like some sort of a disease." The biologists working the case didn't know it was LMBV at 1st, but they immediately began sampling and testing, looking at growth and mortality rates as well as surveying local anglers. From the last time the department sampled Buggs Island Lake in 2004 to this year, he said, "mortality went way up. It was about a 10 percent increase in mortality. And growth declined a little bit."
A total of 41 percent of sampled fish tested positive for the virus, and unlike at Briery so far, they're dying in numbers big enough to impact the fishing, especially for larger bass.
"It's definitely harder on larger fish," Michaelson said. "There's not as many big fish for one thing, so if 40 percent of the population has it, that's 40 percent of a lot fewer fish when you're talking about big fish."
As with many viruses fish can acquire, not much is known about LMBV.
Michaelson said they're not sure how it arrived in Virginia from points much farther south, and right now there's nothing that can be done about it. In places such as Alabama and Texas, it was "about a 3-year cycle where they saw declines and then it improved real rapidly. Hopefully, at Buggs Island, it'll be the same thing."
But he tempered that hopeful thought with this one: "We don't have growth rates like they do in Texas. It may take a little longer to recover than what they saw down there."
Fewer fish and longer waits for dwindling lunkers is the new normal at Kerr Reservoir. At Briery Creek Lake and elsewhere, the fishing holds, but no one knows why or if it will last.
[Byline: Andy Thompson]
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Communicated by:
Thomas James Allen
<tjallen@pipeline.com>
[LMBV is in the family Iridoviridae. There are 4 genus level groups in the Iridoviridae family, _Iridovirus_, _Chloriridovirus_, _Ranavirus_, and _Lymphocystisvirus_. It is not known what genus this specific virus belongs to.
The virus was 1st discovered in Florida but its true origin remains unknown. However the disease has been diagnosed in Texas, Virginia, Tennessee, Oklahoma, Vermont, Mississippi, Indiana, Illinois, Kentucky, South Carolina, North Carolina, Wisconsin, Arkansas, Alabama, Georgia, Missouri, Louisiana and Georgia, in addition to Florida.
Fish that are carriers of the virus may not appear visibly ill. The virus kills largemouth bass, but may not kill other fish that it infects. The disease has been found in guppies, bluegill, crappies, sunfish and smallmouth bass. Some largemouth bass may carry the disease and do well until a stressor effects them. Some stressors include water temperatures above normal, or temperatures above normal for long periods of time, overcrowding, pollution, poor nutrition, other infections and frequent handling by anglers.
The virus can be transmitted through the water, by contact with infected fish, and consumption of prey that may be infected.
Sadly, much remains to learn about this disease, especially how to prevent it or control it.
Portions of this comment were extracted from:
<http://www.in.gov/dnr/files/LMBV.pdf> - Mod.TG]
[The interactive HealthMap/ProMED map for Virginia is available at:
<http://healthmap.org/r/00tK> - CopyEd.EJP]
[see also:
2007
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Largemouth bass virus - USA (KS) 20070812.2623
2004
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Largemouth bass virus - USA (WV) 20040403.0915
2003
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Largemouth bass virus - USA (MI) 20030502.1097 Largemouth bass virus - USA (Louisiana) 20030106.0049
2002
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Largemouth bass virus - USA (Virginia) 20020614.4494 2000
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Largemouth bass virus - USA (Texas) 20000705.1117] ....................tg/ejp/dk
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