Investigation and Disease Prevention of Spring Viremia of Carp Virus (SVCV)
Koi Infected with Spring Viremia of Carp Virus
There has been long history of disease outbreaks and economic losses in wild and farmed carp species due to SVCV. Formerly thought to be restricted to Europe and Asia, SVCV was detected for the first time in North America from diseased koi at a North Carolina fish farm in 2002, and there were extensive eradication efforts with 135,000 fish euthanized in addition to the ~15,000 that died from the disease. Since then nine subsequent detections or outbreaks of SVCV have occurred in North America with the latest fish epidemic in 2010 occurring not only in carp species, but also was reported for the first time from centrachid fish species (bluegill and largemouth bass) and in 2015 the first isolation from an imported amphibian species (salamander) occurred. Thus this exotic virus is considered a threat to native fish populations and now also a potential risk to amphibian species in North America.
SCV virus is listed by the World Organization of Animal Health (OIE) and is considered an exotic virus in United States. Susceptibility testing of various aquatic animal species to this exotic virus, persistence of the virus in its natural fish host species (koi), and development of molecular-based vaccines against SVCV strains are three focus areas of the SVC virus research project. Because of the exotic and invasive potential of SVC virus all live animal research is performed in our high containment aquatic biosafety level three (BSL-3) laboratory. A DNA vaccine based on the North Carolina strain of the SVC virus and recombinant virus construct based on a European SVCV strain were developed and are also being explored as possible therapeutic means of combatting SVC disease.
Three salmonid species (rainbow trout and steelhead trout, Chinook salmon, and sockeye salmon), one perch species, and two cyprinid species (koi and fathead minnows) have been tested with the North Carolina SVCV isolate. Virus challenged salmonid fish had cumulative percent mortalities ranging from 0 to 100%. Yellow perch and fathead minnows suffered moderate mortalities (29% to 33%) after exposure to SVCV. Young sockeye salmon were the most susceptible salmonid species tested, since they experienced the same high level of mortality as the primary host species (koi). This was the first report of SVCV infection in Percidae species and sockeye salmon. Our findings indicated that fish species type and host age were the primary risk factors for susceptibility to SVCV, but climate change and rearing practices may also contribute to infection risk and thus the potential invasiveness of this exotic virus to native North American aquatic animal populations is a real threat.
We continue to evaluate the susceptibility level of various fish species to the virus and have started susceptibility testing of novel aquatic species. Virulence differences between international and domestic SVC virus strains are also being assessed. The results from this research will provide resource managers with knowledge and tools that will enable them to better manage and protect our wild and cultured aquatic animal communities from SVC virus.
Non-USGS Collaborators:
Dr. Sharon Clouthier and Tamara Schroeder, Fisheries and Oceans Canada, Freshwater Institute Science Laboratory, Winnipeg, MB, Canada
Dr. George Sanders, Department of Comparative Medicine, School of Medicine, University of Washington, Seattle, WA, USA
Michel Brémont, Stéphane Biacchesi, and Emilie Mérour, French National Institute for Agricultural Research (INRA), Jouy en Josas, France
Peng Jia and Hong Liu, Key Laboratory of Aquatic Animal Diseases, Shenzhen Exit & Entry Inspection and Quarantine Bureau, Shenzhen, China
There has been long history of disease outbreaks and economic losses in wild and farmed carp species due to SVCV. Formerly thought to be restricted to Europe and Asia, SVCV was detected for the first time in North America from diseased koi at a North Carolina fish farm in 2002, and there were extensive eradication efforts with 135,000 fish euthanized in addition to the ~15,000 that died from the disease. Since then nine subsequent detections or outbreaks of SVCV have occurred in North America with the latest fish epidemic in 2010 occurring not only in carp species, but also was reported for the first time from centrachid fish species (bluegill and largemouth bass) and in 2015 the first isolation from an imported amphibian species (salamander) occurred. Thus this exotic virus is considered a threat to native fish populations and now also a potential risk to amphibian species in North America.
SCV virus is listed by the World Organization of Animal Health (OIE) and is considered an exotic virus in United States. Susceptibility testing of various aquatic animal species to this exotic virus, persistence of the virus in its natural fish host species (koi), and development of molecular-based vaccines against SVCV strains are three focus areas of the SVC virus research project. Because of the exotic and invasive potential of SVC virus all live animal research is performed in our high containment aquatic biosafety level three (BSL-3) laboratory. A DNA vaccine based on the North Carolina strain of the SVC virus and recombinant virus construct based on a European SVCV strain were developed and are also being explored as possible therapeutic means of combatting SVC disease.
Three salmonid species (rainbow trout and steelhead trout, Chinook salmon, and sockeye salmon), one perch species, and two cyprinid species (koi and fathead minnows) have been tested with the North Carolina SVCV isolate. Virus challenged salmonid fish had cumulative percent mortalities ranging from 0 to 100%. Yellow perch and fathead minnows suffered moderate mortalities (29% to 33%) after exposure to SVCV. Young sockeye salmon were the most susceptible salmonid species tested, since they experienced the same high level of mortality as the primary host species (koi). This was the first report of SVCV infection in Percidae species and sockeye salmon. Our findings indicated that fish species type and host age were the primary risk factors for susceptibility to SVCV, but climate change and rearing practices may also contribute to infection risk and thus the potential invasiveness of this exotic virus to native North American aquatic animal populations is a real threat.
We continue to evaluate the susceptibility level of various fish species to the virus and have started susceptibility testing of novel aquatic species. Virulence differences between international and domestic SVC virus strains are also being assessed. The results from this research will provide resource managers with knowledge and tools that will enable them to better manage and protect our wild and cultured aquatic animal communities from SVC virus.
Non-USGS Collaborators:
Dr. Sharon Clouthier and Tamara Schroeder, Fisheries and Oceans Canada, Freshwater Institute Science Laboratory, Winnipeg, MB, Canada
Dr. George Sanders, Department of Comparative Medicine, School of Medicine, University of Washington, Seattle, WA, USA
Michel Brémont, Stéphane Biacchesi, and Emilie Mérour, French National Institute for Agricultural Research (INRA), Jouy en Josas, France
Peng Jia and Hong Liu, Key Laboratory of Aquatic Animal Diseases, Shenzhen Exit & Entry Inspection and Quarantine Bureau, Shenzhen, China