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Largemouth Bass Virus: An Expanding
Problem?
John A. Plumb, John M.
Grizzle, Andrew Noyes, and Jason Woodland Southeastern
Cooperative Fish Disease Project, Department of Fisheries and Allied Aquacultures, Auburn University, Alabama 36849
The largemouth bass virus (LMBV), genus
Ranavirus, family Iridoviridae,was first isolated from
wild largemouth bass Micropterus
salmoides in a South Carolina reservoir in 1995. In a 1997-1998 survey of wild largemouth bass in eight southeastern
states LMBV was isolated from ostensibly healthy fish from six reservoirs in
Georgia and Alabama, healthy and moribund largemouth bass in one reservoir in
Georgia and moribund fish in a reservoir in South Carolina. The survey included 457 fish from 78 rivers,
reservoirs and hatcheries. Largemouth
bass virus has since been isolated from moribund largemouth bass in
Mississippi, Louisiana, Missouri, Texas, and Tennessee; other pathogens were
found in fish from some locations. A
virus (presumably LMBV) was also recently isolated from apparently healthy
largemouth bass and other centrarchids from Florida, Kentucky and North
Carolina. Viruses from the 1997-98
survey had DNA sequences identical to the original LMBV isolate and all of
these viruses thus far tested by PCR appear to be LMBV. Largemouth bass virus is very similar to
viruses isolated from guppy Poecilia
reticulata and doctor fish (species uncertain) in California in the early
1990's. Most LMBV isolates have come
from adult largemouth bass but experimentally it causes mild to severe disease
in juvenile largemouth bass.
Experimentally infected juvenile fish yield high titers of LMBV (>106
TCID50/g of tissue) and lesions are confined to the injection site
and peritoneal cavity. Largemouth bass virus has minimal effect on other fish
species (striped bass, bluegill and grass carp) that have been exposed in
laboratory experiments. Clearly, the
geographical range, and possible species susceptibility, of LMBV has expanded
since its discovery in 1995. Whether or
not LMBV is a major disease problem in wild or hatchery largemouth bass
populations is unclear, however, there is a high degree of interest in the
virus from sportfish organizations, state and federal fishery management
agencies and the scientific community.
Only time will tell if LMBV poses a serious problem, deserves
consideration by fishery managers, or is a disease of little consequence.
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