The US Geological Survey reported August 13 that a virus known to cause illness in largemouth bass (Micropterus salmoides) has also been found in northern snakeheads (Channa argus), an invasive species now found in the Chesapeake Bay. This discovery comes from a USGS and Virginia Department of Game and Inland Fisheries study on introduced pathogens in northern snakeheads in Virginia. The virus has previously been discovered in other fish species, including sunfish, but has only been shown to cause disease in largemouth bass.
The first reported case of Largemouth Bass virus (LMBV) in the United States was from Florida in 1991; since then, it has been found throughout the eastern, southern, and Midwestern states. Scientists are still unsure of how it originated and why it only causes disease in largemouth bass, but not in other species. When it does cause illness, affected fish often have trouble swimming and staying upright and can be seen floating near the surface of the water. LMBV belongs to a group of viruses called ranaviruses, which cause lethal illness in amphibians.
The discovery of LMBV in northern snakeheads is concerning because the range of this species overlaps with largemouth bass in the Chesapeake Bay watershed. While the snakeheads do not appear to become diseased from the virus, they can carry it and increase transmission to largemouth bass in the area, potentially putting the health of bass populations in danger.
In order to fully understand the implications of this discovery, scientists will need to learn more about the virus itself, such as the mode of transmission, before they can determine the risk for bass populations. Bassmaster, a fishing website, assures that infected fish are no threat to humans; the virus has not been shown to affect either humans or other warm-blooded animals.
Identification of Largemouth Bass Virus in the Introduced Northern Snakehead Inhabiting the Chesapeake Bay Watershed. http://www.tandfonline.com/doi/abs/10.1080/08997659.2013.799614?journalCode=uahh20 - .UgqBuWT5kYU
Largemouth Bass Virus Found in Northern Snakeheads in Virginia. http://www.usgs.gov/newsroom/article.asp?ID=3662
Largemouth bass virus (LMBV) fact sheet. http://www.bassmaster.com/news/largemouth-bass-virus-lmbv-fact-sheet