LARGEMOUTH BASS VIRUS COMMON

COMMON NAME: Largemouth Bass Virus
Some other common names have been suggested for Largemouth Bass Virus (LMBV),
like Lake Weir iridovirus, Lake Weir ranavirus, and Santee-Cooper ranavirus. These
names credit the water bodies where the virus was first isolated, Lake Weir, and the
reservoir where the first fish kill occurred, Santee-Cooper Reservoir. As of now
Largemouth Bass Virus is the accepted common name.
SCIENTIFIC NAME: Virus
LMBV is in the family Iridoviridae. There are four genus level groups in the Iridoviridae
family, Iridovirus, Chloriridovirus, Ranavirus and Lymphocystisvirus. It is not known
what genus this specific virus belongs to.
DISTRIBUTION: The origin of LMBV is unknown. It was first discovered in the
United States in Florida. It has since been detected in 18 other states including Alabama,
Arkansas, Georgia, Illinois, Indiana, Kentucky, Louisiana, Michigan, Missouri,
Mississippi, North Carolina, Oklahoma, South Carolina, Tennessee, Texas, Virginia,
Vermont and Wisconsin.
Indiana: In Indiana the first confirmed case of LMBV was in 2000 at Lake
George which lies on the Indiana/Michigan border. A largemouth bass die off at
the lake prompted testing of the fish which showed the fish were positive for
LMBV. Subsequent bass mortality with the fish testing positive for LMBV were
found at Hamilton Lake (Steuben Co.), Little Long Lake (Indiana/Michigan
border), Dewart Lake (Kosciusko Co.), Chapman Lake (Kosciusko Co.),
Dogwood Lake (Davies Co.), and Starve Hollow Lake (Jackson Co.).
DESCRIPTION: The signs of a fish infected with LMBV are sometimes hard to
recognize. Some carriers of the virus will seem completely normal. If the virus has
triggered disease in a fish that fish will be near the surface, having trouble staying
upright, and having difficulty swimming. LMBV seems to infect the swim bladder of
fish. Some bladders will have a thick yellow or brown exude, or it could only be slightly
red and over inflated, and sometimes the swim bladder will look normal. For precise
diagnosis a DNA based test must be preformed.
LIFE CYCLE BIOLOGY: LMBV does not only infect largemouth bass, it also has
been found in guppies, smallmouth bass, spotted bass, Suwanee bass, bluegill,
redbreasted sunfish, white crappie and black crappie. This virus usually only causes
death in largemouth bass. It is unknown why this virus kills largemouth bass and not
other fish. Often largemouth bass infected with LMBV will show no signs of disease. It
is believed that stress triggers the disease of the virus. Stressful factors include hot
weather, poor water quality, pollution, crowding in livewell tanks, frequent handling by
anglers, and other pathogens. The virus attacks the swim bladder of infected individuals.
Besides fish, LMBV has been found in other cold-blooded animals like amphibians and
reptiles. LMBV has never been detected in warm-blooded animals, including humans.
Infected fish are edible as long as they are cooked properly.
PATHWAYS/HISTORY: This virus was first isolated in Lake Weir in Florida in 1991.
A fish kill in Santee-Cooper Reservoir of South Carolina occurred in 1995 and LMBV
was detected. In 1998, kills occurred in Alabama, Georgia, South Carolina, Mississippi
and Texas. In 1999, fish kills were reported from Missouri, Arkansas, Mississippi, two
Largemouth Bass Virus
from Texas and two in Louisiana. Arkansas, Oklahoma, Louisiana, Michigan, Illinois,
Wisconsin, Vermont and Indiana all suffered losses from 2000 to 2002. Since then
Virginia, North Carolina, Tennessee and Kentucky all joined the list of states that have
detected LMBV.
DISPERSAL/SPREAD: It seems that LMBV can be transmitted through the water, fish
to fish contact, and by consuming infected prey. Because LMBV can survive in the
water for up to seven days, it can be transferred in the live wells of boats. Other fish
carry the disease so infected but not diseased fish could be stocked and transfer the virus
into new waters. The virus is present in the cutaneous mucus of infected fish which
allows for spread by fish to fish contact.
RISKS/IMPACTS: A disease outbreak of LMBV usually attacks adult largemouth bass
which causes concern among anglers. Anglers are worried that this virus could damage
the fishery at their favorite fishing spot. Usually the number of fish that die from the
disease is relatively low compared to the entire population. Fishing may be poor
following a fish kill but it is thought that there are no long-term effects on largemouth
bass populations. Fish kills only seem to occur during or after stressful situations, so
theoretically a fish could be carrying the virus but feel none of the effects. Much has yet
to be learned about LMBV so precautions should be taken to ensure that this virus does
not spread into new waters.
MANAGEMENT/PREVENTION: There is nothing that can be done to eradicate
LMBV in the wild. What we can do is educate the public on how to prevent the spread of
this virus and ways to minimize its impacts. We also need to learn more about the virus
so we can then turn to finding ways to manage it. You can reduce the likelihood of
spreading this disease if you follow a few simple guidelines.
􀀹 Dispose of all unused bait in the trash or on land, never into the water.
􀀹 Never transfer live fish from one body of water to another.
􀀹 Never discard fish entrails or skeletal parts in a body of water.
􀀹 Rinse any mud and/or debris from equipment and wading gear and drain any
water from boats before leaving the launch area. Remember that LMBV can live
for seven days in water so this step is important.
􀀹 Handle bass gently if you intend to release them.
􀀹 Stage fishing tournaments in cooler weather to reduce stress on caught bass.
􀀹 If you see any dead or dying fish, report your observation to the district fisheries
biologist so that they may be tested for the virus.