Photo credit: Kenyon College

Largemouth Bass Virus (LMBV)


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If you believe you have found this species anywhere in Pennsylvania, please report your findings to state and federal authorities immediately!

Species at a Glance

This virus is from the family Iridoviridae and is known to cause lethal disease to wild, adult largemouth bass (Micropterus salmonides) in the eastern United States. Many bass that carry LMBV may never develop disease and appear completely normal.


When the virus causes disease, symptoms may include increased blood flow and darkened skin, distended abdomen, bloated swim bladder, lesions in the membrane lining the body cavity, pale liver, red spleen, infected gills, lethargic swimming, decreased responsiveness, swimming at the surface and/or in circles, difficulty remaining upright, and death. Disease usually occurs during warmer months in the summer when bass are physically stressed.

Similar Species

The virus has not reportedly caused disease in any other species except largemouth bass.


LMBV is easily transferred from one infected bass to another, and among several other species of fish including sunfish and snakeheads. LMBV does not infect warm-blooded species.

Environmental Impacts

The largemouth bass virus is known to cause lethal disease to wild, adult largemouth bass (Micropterus salmonides) in the eastern United States. Cases of disease and mortality are usually followed by individuals developing antibodies, allowing the population to recover within five to seven years.


Information for this species profile comes from the Mid-Atlantic Field Guide to Aquatic Invasive Species (2016).

The Pennsylvania iMapInvasives Program is a partnership of the Western Pennsylvania Conservancy, the Pennsylvania Natural Heritage Program, and NatureServe.

Funding for Pennsylvania iMapInvasives is provided by the Great Lakes Restoration Initiative.

NatureServe logo, iMapInvasives partner
Pennsylvania Natural Heritage Program, iMapInvasives partner
Great Lakes Restoration Initiative logo, iMapInvasives funding source