Piscirickettsia cf. salmonis
Common Name:
Muskie pox
Synonyms and Other Names:
Known in salmonids as piscirickettsiosis, salmon rickettsia syndrome, salmonid rickettsial septicemia, or SRS
PLO in agency reports indicates 'piscirickettsia-like-organism' which may be this species as well.
Identification:
P. salmonis are aerobic Gram-negative bacteria occurring intracellularly in fish, primarily salmonids. The bacteria are usually coccoid (but sometimes occur in paired rods or in rings), fastidious (with very specific growth requirements), and non-motile (Mauel and Miller 2002; Fryer and Hedrick 2003). P. salmonis bacteria isolated from Muskellunge (Esox masquinongy) in Lake St. Clair only occur as curved rods and rings (Michigan DNR 2007).
P. salmonis in salmonids can result in anemia, kidney necrosis, enlarged spleen, hemorrhages, nodules or crater-form lesions in the liver, dark coloration, skin lesions, lack of appetite, anorexia, and lethargic swimming activity. Symptoms vary in different populations and some fish display no external symptoms at all (Mauel and Miller 2002; Fryer and Hedrick 2003; Rise et al. 2004). In Lake St. Clair, infected Muskellunge can exhibit red skin lesions (Michigan DNR 2007).
Size:
P. salmonis is 0.5-1.5 µm in diameter (Fryer and Hedrick 2003).
Native Range:
Unknown. The geographic range of P. salmonis could be broad. It could be native to marine environments, including parts of the Pacific and Atlantic oceans; however, some of the marine regions in which it now occurs could constitute introductions (Fryer and Hedrick 2003).
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This map only depicts Great Lakes introductions.
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Great Lakes Nonindigenous Occurrences:
Piscirickettsia cf. salmonis was first detected in the Great Lakes from Muskellunge (Esox masquinongy) in Lake St. Clair in May 2002 (MDNR 2004).
Table 1. Great Lakes region nonindigenous occurrences, the earliest and latest observations in each state/province, and the tally and names of HUCs with observations†. Names and dates are hyperlinked to their relevant specimen records. The list of references for all nonindigenous occurrences of Piscirickettsia cf. salmonis are found here.
Table last updated 5/1/2024
† Populations may not be currently present.
Ecology:
P. salmonis survives and replicates asexually through fission in the membrane-bound vacuoles inside the cytoplasm of host fish cells. It has not been isolated from gametes suggesting vertical transmission does not occur (Thomas and Faisal 2009). It can rarely be passed from adult to young and is likely passed more frequently from adult to adult, entering through the skin or gills. It is inactive above 20°C and replication is optimal at 15–18°C. It survives better in saltwater than in freshwater, remaining infective for up to 14 days in the former but quickly becoming unstable in the latter (Smith et al. 1999; Mauel and Miller 2002; Fryer and Hedrick 2003; Larenas et al. 2003; Mauel et al. 2003; Smith et al. 2004).
Organisms that are piscirickettsia-like or rickettsia-like (including all fastidious, intracellular fish pathogens) are labeled PLOs or RLOs (Mauel and Miller 2002). PLOs and RLOs are associated with disease in many fish species. Some PLOs are genetically very similar to P. salmonis; a PLO that is 98% similar to typical P. salmonis has been isolated at 10 m depth in bacterioplankton from the coastal waters of Oregon (Mauel and Fryer 2001).
P. salmonis causes mortality in salmonids, killing millions of hatchery farmed fish each year. As for many diseases that naturally occur in the wild, infection becomes more severe in crowded aquaculture settings. Coho salmon (Oncorhynchus kisutch) are highly susceptible while Atlantic salmon (Salmo salar) are less susceptible. P. salmonis has also been reported in Rainbow trout (O. mykiss), Cherry salmon (O. masou), Chinook salmon (O. tschwaytscha), and Pink salmon (O. gorbuscha), and can probably infect all salmonids (Mauel and Fryer 2001; Mauel and Miller 2002; Fryer and Hedrick 2003; Birkbeck et al. 2004; Rise et al. 2004).
In addition to the occurrence in freshwater Muskellunge in Lake St. Clair, PLOs and RLOs have also been found in: -blue-eyed plecostomus (Panaque suttoni), a tropical freshwater fish shipped from Columbia to the USA (Khoo et al. 1995); -seabass (Dicentrarchus labrax) in the Mediterranean Sea (Comps et al. 1996; Athanassopoulou et al. 1999; McCarthy et al. 2005); -white sea bass (Atractoscion nobilis) off the coast of southern California (Chen et al. 1999; Arkush et al. 2005; Arkush et al. 2006); -puffers (Tetrodon fahaka) from the Nile River in Egypt (Mauel and Miller 2002); -dragonets (Callionymus lyra) from coastal Wales (Mauel and Miller 2002); -tilapia (Oreochromis mossambicus and Sarotherodon melanotheron) in Taiwan, Jamaica, Indonesia, Florida, California, and Hawaii (Chern and Chao 1994; Mauel and Miller 2002); -and in groupers (Epinephelus melanostigma) in Taiwan (Chen et al. 2000).
P. salmonis was not isolated from salmonids in the freshwater stage of their life cycle until 1993 in Chile. The disease was very similar to P. salmonis occurring in fish held in marine aquaculture pens. It could have been transmitted to the fish being cultured in freshwater from brood stock that had survived an outbreak of P. salmonis in a marine environment, or it could have already been present in the freshwater culture environment (Gaggero et al. 1995). The PLO infection of Muskellunge in Lake St. Clair is unique, given that it occurred in wild fish. Other fish affected by P. salmonis and PLOs or RLOs have typically been cultured and many have been species that spend at least part of their life cycle in marine environments.
Means of Introduction:
Unknown
Status:
Established
Great Lakes Impacts:
Summary of species impacts derived from literature review. Click on an icon to find out more...
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Piscirickettsia cf. salmonis has a moderate environmental impact in the Great Lakes. Realized:
Piscirickettsia cf. salmonis infections have been limited in the Great Lakes to Muskellunge (E. masquinongy) and Yellow perch (Perca flavescens) from Lake St. Clair (Hartig 2006, Thomas and Faisal 2009, MDNR 2004). The bacterium was detected in all of the fish sampled (n=26) from Lake St. Clair during a large Muskellunge die-off in 2003. No subsequent mortalities were observed in St. Clair until 2006 (Hartig 2006, Thomas and Faisal 2009). Piscirickettsia cf. salmonis infection rates in Lake St. Clair Muskellunge have been found to be over 80 percent in fish larger than 1,000 mm and or older than 8 yrs (2004-2007; Thomas and Faisal 2009). Piscirickettsia cf. salmonis has also been isolated from Yellow perch (P. flavescens) from Lake St. Clair with infection rates as high as 57 percent. Analysis of the two isolates from Muskellunge and Yellow perch indicate both are identical (Thomas and Faisal 2009). However, surveys of P. cf. salmonis infected waters in the Great Lakes do not indicate substantial negative impacts on native fish populations (MDNR 2004, WDNR 2012).
Piscirickettsia cf. salmonis infections can result in anemia, kidney necrosis, an enlarged spleen, hemorrhaging, nodules or crater-form lesions in the liver, skin lesions, anorexia, and lethargy (Fryer and Hedrick 2003, Mauel and Miller 2002, Rise et al. 2004). Because of this, infected fish are more susceptible to predation (Lafferty and Morris 1996), which could result in indirect effects on the food web and ecosystem. Die-offs of apex predators such as Muskellunge may have severe impacts on the Great Lakes food web.
There is little or no evidence to support that Piscirickettsia cf. salmonis has significant socio-economic impacts in the Great Lakes.
Potential:
Piscirickettsia cf. salmonis infections in cultured Atlantic salmon (Salmo salar) from the Pacific and Atlantic coasts of Canada have led to population mortality levels of 0.6-15% (Evelyn 1992, Olsen et al. 1993, Rodger and Drinan 1993). However, no such infections have been realized in Great Lakes Atlantic salmon. Atlantic salmon are considered less susceptible to infection and mortality; in contrast, Coho salmon (Oncorhynchus kisutch), Rainbow trout (O. mykiss), and Chinook salmon (O. tschwaytscha) are more susceptible (Birkbeck et al. 2004, Fryer and Hedrick 2003, Mauel and Fryer 2001, Mauel and Miller 2002, Rise et al. 2004). Infections in non-native salmonids have not been realized in the Great Lakes.
Chilean aquaculture facilities have experienced mortality due to P. cf. salmonis in 30-90% of reared Coho salmon (Bravo and Campos 1989). As a result, this industry has shifted their cultures to Atlantic salmon (Reid et al. 2004). If similar effects are realized in the Great Lakes, significant economic impacts could be realized.
While impacts to the sport fishing industry by P. cf. salmonis have not yet been realized, such effects could be significant. For example, recreational fishing on Lake St. Clair can generate $23 million annually (Thomas and Faisal 2009).
There is little or no evidence to support that Piscirickettsia cf. salmonis has significant beneficial effects in the Great Lakes.
Management:
Regulations (pertaining to the Great Lakes)
Piscirickettsia salmonis is listed as a provisional pathogen by the Great Lakes Fishery Commission. If found in the wild it should be reported to the Great Lakes Fish Health Committee Chair. Risk assessment is recommended before using as broodstock. If detected in a hatchery, a risk assessment should be used to determine whether it should be transferred or stocked. Action should be taken to minimize spread.
Note: Check federal, state/provincial, and local regulations for the most up-to-date information.
Control
Biological
Vaccines derived from inactivated P. cf. salmonis bacterins are considered ineffective against the bacterium. However, vaccines being developed using recombinant DNA have promise in combating P. salmonis infections (Corbeil and Crane 2009). Further research is required to understand the practical application of this therapy.
Physical
Culling is effective at preventing horizontal transmission of P. cf. salmonis (Torenzo et al. 2005).
Chemical
Epoetin Alfa can reduce mortality rates in P. cf. salmonis infected Pacific salmon (Torenzo et al. 2005). All commonly used aquaculture disinfectants are considered effective against Piscirickettsia spp. (Corbeil and Crane2009, Fryer et al. 1990, Fryer et al. 1992). Antimicrobial agents used to treat P. salmonis include oxolinic acid and flumequin (Corbeil and Crane 2009, Guardabassi and Courvalin 2006, Todar 2008).
Other
Establishment of Muskellunge fingerling index surveys may help monitor trends in spawning success and or fingerling survival (Thomas and Faisal 2009).
Note: Check state/provincial and local regulations for the most up-to-date information regarding permits for control methods. Follow all label instructions.
References
(click for full reference list)
Other Resources:
Author:
Kipp, R.M., A.K.Bogdanoff, A. Fusaro and R. Sturtevant.
Contributing Agencies:
Revision Date:
8/17/2018
Citation for this information:
Kipp, R.M., A.K.Bogdanoff, A. Fusaro and R. Sturtevant., 2024, Piscirickettsia cf. salmonis: U.S. Geological Survey, Nonindigenous Aquatic Species Database, Gainesville, FL, and NOAA Great Lakes Aquatic Nonindigenous Species Information System, Ann Arbor, MI, https://nas.er.usgs.gov/queries/greatLakes/FactSheet.aspx?Species_ID=2658&Potential=N&Type=0&HUCNumber=DGreatLakes, Revision Date: 8/17/2018, Access Date: 5/2/2024
This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.