R. salmonina, Corynebacterium salmoninus, corynebacterial kidney disease, salmonid kidney disease

Summary of species impacts derived from literature review. Click on an icon to find out more...

Environmental	Socioeconomic	Beneficial

Realized:

Great Lakes native salmonid species that have tested positive for the bacterium include Atlantic salmon (Salmo salar), lake trout (Salvelinus namaycush), brook trout (S. fontinalis), and splake (S. fontinalis x S. namaycush) (GLFHC 2006, GLFHC 2012, Hay 2003, Jonas et al. 2002, Nuhfer et al. 2005, Starliper et al. 1997). Lake trout and brook trout are considered less susceptible to R. salmoninarum infection and may not experience mortality upon contracting BKD; in contrast, Atlantic salmon are more susceptible and prone to mortality (Hay 2003, Jonas et al. 2002, Nuhfer et al. 2005, Starliper et al. 1997).

Other Great Lakes native species found harboring R. salmoninarum include lake whitefish (Coregonus clupeaformis), bloater (C. hoyi), lake herring (C. artedi), mottled scuplin (Cottus bairdi), white sucker (Catostomus commersonii), muskellunge (Esox masquinongy), channel catfish (Ictalurus punctatus), lake sturgeon (Acipenser fulvescens), and walleye (Sander vitreus) (COSEWIC 2005, GLFHC 2006, GLFHC 2012, Hay 2003, Jonas et al. 2002, Nuhfer et al. 2005, Starliper et al. 1997). Four of the Great Lakes native species (splake, muskie, channel catfish, and lake sturgeon) represent new detections since 2005. Lake whitefish and bloater are believed to be less susceptible to R. salmoninarum infection and may not experience mortality upon contracting BKD (Hay 2003, Jonas et al. 2002, Nuhfer et al. 2005, Starliper et al. 1997). However, strains of the bacterium isolated from Lake Michigan have been found to be more virulent than those from the Pacific Northwest (Austin and Austin 1987, Grayson et al. 1999, Jonas et al. 2002, Starliper et al. 1997, Thomas et al. 1999) and in some cases have resulted in higher than anticipated levels of infection (e.g., Nalepa et al. 2005).

While R. salmoninarum affects multiple Great Lakes native species, as of 2006, prevalence and mortalities in infected fish had been relatively low (GLFHC 2006). However, more recent data from 2011 indicates that this bacterium has become more widely distributed with varying prevalence throughout Michigan state hatcheries and wild populations. The bacterium was detected in brook trout at 1.7% to 54% prevalence; Atlantic salmon 1.7% to 50%; muskellunge, lake sturgeon, and channel catfish at 1.7% to 10%; and lake trout, splake, and lake herring at 1.7%-5% prevalence (GLFHC 2012). That same year, R. salmoninarum was detected at low prevalence in Minnesota hatcheries and for the first time in lake trout from Mountain Lake, MN. The Minnesota Department of Natural Resources is considering whether or not to continue using that lake as a brood stock source (GLFHC 2012).

Renibacterium salmoninarum is considered to be endemic in Ontario and is found in OMNR fish culture facilities at low levels (GLFHC 2012).

Potential:
Symptoms of BKD include abdominal fluid build-up and swelling, pseudomembranes and hemorrhaging on viscera, kidney and gill necrosis, intestinal hemorrhaging, ulcers or abscesses in muscles, protruding eyeballs, anemia, blood blisters, and lesions of the eyes, liver, spleen, and heart (Austin and Austin 1987, Holey et al. 1998). Because of this, infected fish may be more susceptible to predation (Lafferty and Morris 1996). However, cascading food web effects as a result of BKD infection in the Great Lakes have not been reported.

Renibacterium salmoninarum has a high socio-economic impact in the Great Lakes.
Realized:
Lake whitefish (C. clupeaformis) collected from Lake Michigan and Lake Huron between 2003 and 2006 tested positive for R. salmoninarum at 62.31% prevalence. Lake whitefish have a high commercial value in the Great Lakes (Nalepa et al. 2005), and if as a result of BKD infection, populations were to fluctuate significantly, there could be serious economic effects.

Great Lakes non-native species that have tested positive for R. salmoninarum include Chinook salmon (Oncorhynchus tshawytscha) (Holey et al. 1998), coho salmon (O. kisutch), and rainbow trout (O. mykiss) (Jonas et al. 2002). Rainbow trout (O. mykiss) is less susceptible to BKD infection and may not experience mortality upon contracting the disease, whereas coho salmon (O. kisutch) and Chinook salmon (O. tshawytscha) are more susceptible to infection and more prone to mortality (Hay 2003, Jonas et al. 2002, Nuhfer et al. 2005, Starliper et al. 1997).

Prevalence rates of R. salmoninarum were up to 100% in some parts of the Lake Michigan drainage around 1986. This outbreak of BKD caused heavy mortality in Chinook salmon in 1988 and persisted in the population until 1992. That year, boat fisheries observed at least a 40% decline in Chinook salmon catch per unit effort levels. By 1993, catch per unit effort was 15% of the peak observed in 1986 (Holey et al. 1998). In 1986, the Strawberry Creek spawning weirs in Wisconsin documented no presence of R. salmoninarum. In 1988, the bacterium was isolated in 67% of the returning Chinook salmon and then persisted at moderate levels through 1992 (Holey et al. 1998). The 1980s’ mortality events are believed to have also been influenced by increased vulnerability due to food shortages, particularly alewives (Alosa pseudoharengus), high Chinook salmon density, and high parasite loads (Holey et al. 1998). While significant for the fisheries at that time, given the magnitude of the stocks present in Lake Michigan, it is improbable that the Chinook salmon die-offs observed in the late 1980s and early 1990s caused a residual demographic bottleneck in those populations (Weeder et al. 2005).

As of 2006, the overall prevalence of R. salmoninarum in non-native Great Lakes species was thought to be low and declining over time (GLFHC 2006, Jonas et al. 2002). However in 2011, R. salmoninarum was widely distributed with varying prevalence throughout Michigan state hatcheries and wild populations. The bacterium was detected in brown trout (Salmo trutta) at 1.7% to 54% prevalence, rainbow trout at 1.7% to 40%, coho salmon at 1.7% to 10%, and Chinook salmon at 1.7% to 5% prevalence (GFLHC 2012).

Renibacterium salmoninarum was detected in 11 of 12 production lots of rainbow trout and coho salmon from 4 of 5 Indiana state hatcheries with prevalence ranging from 1.67% to 26.67%, with six cases exceeding 10% (GLFHC 2012).

Potential:
Bloater (C. hoyi) is a staple of Great Lakes native and non-native salmonid diets. Reductions in salmonid populations and economic effects to the Great Lakes fishing industry could be realized if bloater populations decline (Wyns 2002).

There is little or no evidence to support that Renibacterium salmoninarum has significant beneficial effects in the Great Lakes.
Realized:
In addition to commercially valuable non-native Great Lakes species (see Socio-economic Impacts), sea lamprey (Petromyzon marinus) has tested positive for BKD (Eissa et al. 2006). However, infection is not likely to control sea lamprey populations.

Regulations: (pertaining to the Great Lakes)
Ohio requires source facilities outside the Great Lakes basin to document annual health inspections showing no BKD occurrences for the previous five years prior to importing salmonids to the Lake Erie watershed (Baird 2005). Indiana requires source facilities outside the basin to document they are BKD free prior to importing salmonid stock. Asymptomatic salmonids found carrying the pathogen can be sold in-state if source facilities are within the Great Lakes basin (Baird 2005). Michigan, Illinois, Wisconsin, and Minnesota also require imported salmonid health inspections (NCRAC 2010). Minnesota allows the importation of infected eggs, if prior egg treatments have been approved (Baird 2005).
New York, Pennsylvania, Ohio, Michigan, Indiana, Illinois, Wisconsin, and Minnesota have instated similar baitfish regulations to control the spread of BKD and other fish pathogens. Those of New York include that bait harvested from inland waters for personal use is only permitted to be used within the same body of water from which it was taken and cannot be transported overland (with the exception of smelt, suckers, alewives, and blueback herring). Once transported, baitfish cannot be replaced to its original body of water (NYSDEC 2012).

Live or frozen bait harvested from inland New York waters for commercial purposes is only permitted to be sold or possessed on the same body of water from which it was taken and cannot be transported over land unless under a permit and or accompanied by a fish health certification report. Bait that is preserved and packaged by any method other than freezing, such as salting, can be sold and used wherever the use of bait fish is legal as long as the package is labeled with the name of the packager-processor, the name of the fish species, the quantity of fish packaged, and the means of preservation (NYSDEC 2012).

Certified bait may be sold for retail and transported overland as long as the consumer maintains a copy of a sales receipt that contains the name of the selling vendor, date sold, species of fish sold, and quantity of fish sold. Bait that has not been certified may still be sold but the consumer must maintain a sales receipt containing the body of water where the bait fish was collected and a warning that the bait cannot be transported by motor vehicle. Bait sold for resale require a fish health certification along with a receipt that contains the name of the selling vendor, date sold, species of fish sold, and quantity of fish sold, which must be kept for 30 days or until all bait is sold (NYSDEC 2012).

In addition to baitfish protections, prior to placing fish in New York waters, a fish health certification report must document that the fish are BKD free.

Note: Check federal, state/provincial, and local regulations for the most up-to-date information.

Control
Biological
There are no known biological control methods for this species.

Physical
Culling infected stock has reduced the prevalence of R. salmoninarum in aquaculture (Gudmundsdóttir et al. 2000, Maule et al. 1996, Pascho et al. 1991).

Chemical
Antimicrobial agents used to treat R. salmoninarum include nitrofurans, bacitracin, chlortetracycline, oxytetracycline, novobiocin (Wolf and Dunbar 1959), cephalosporins, gentamicin, clindamycin, lincomycin, oleandomycin, kitasamycin, spiramycin, penicillin (Austin 1985), cefazolin, tiamulin (Bandín et al. 1991), cephradine, rifampicin, (Brown et al. 1990), tetracycline (Austin 1985, Bandín et al. 1991), chloramphenicol (Austin 1985, Wolf and Dunbar 1959), and erythromycin (Austin 1985, Bandín et al. 1991, Lee and Evelyn 1994, Wolf and Dunbar 1959).

Erythromycin-enhanced feed administered at 100 mg/kg/day for 21 days (Wolf & Dunbar 1959) or for 10 days (Austin 1985) is believed to be the most effective treatment for bacterial kidney disease (Hirvela-koski 2005).  Erythromycin phosphate is an effective chemoprophylaxis in pre-spawning adult brood fish. Subcutaneous injections of 11 mg/kg (Hirvela-koski 2005) or 20 mg/kg (Gudmundsdóttir et al. 2000, Pascho et al. 1991) administered to fish entering trapping facilities and at 21-30 day intervals thereafter (Hirvela-Koski 2005) has reduced mortality in re-spawning Pacific salmon by 10-50% (Groman and Klonz 1983). However, this treatment does not effectively destroy the pathogen from all eggs (Brown et al. 1990). A study by Lee and Evelyn (1994) showed female coho salmon treated with 20 mg/kg erythromycin prior to spawning yielded no vertical transmission of BKD. Treatment success relies on careful timing of the injections in adult salmonids before spawning (Elliott et al. 1989).

Disinfecting eggs with 100 mg/L of iodine for 15 minutes may not eliminate vertical transmission, but can reduce the severity of the disease (Bullock et al. 1978). Treating eggs with iodine at 250 or 500 mg/L for 15-120 minutes is effective at eliminating R. salmoninarum. However, after treatment, variable numbers of R. salmoninarum cells have survived. This is due to cells within the cell aggregates never coming in contact with the iodine (Evelyn et al. 1984, 1986). Renibacterium salmoninarum is inactivated by free chlorine (≤0.05 mg/L), which can be used as a disinfectant and to treat intake and effluent (Pascho et al. 1995).

Other
Prevention is the preferred control method of BKD in cultured stocks (OIE 2003).

Note: Check state/provincial and local regulations for the most up-to-date information regarding permits for control methods. Follow all label instructions.