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Spring viremia of carp (SVC)

By the koi.wiki editorial team · Updated

Key facts: Spring viremia of carp (SVC) is a disease of koi and other cyprinid fish caused by Rhabdovirus carpio (also called Sprivivirus cyprinus or Carp sprivivirus), a bullet-shaped RNA rhabdovirus that typically causes outbreaks in cool spring water temperatures[1][2]. It is listed as a notifiable disease by the World Organisation for Animal Health (WOAH) and is reportable in the United States and Canada[1][3][4].
Spring viremia of carp (SVC) is caused by a bullet-shaped RNA rhabdovirus historically known as Rhabdovirus carpio and now also referred to as Carp sprivivirus or Sprivivirus cyprinus[1][5]. The disease, sometimes called infectious dropsy of carp or swim bladder inflammation, has long been present in Europe, the Middle East, and Russia, and was first confirmed in the United States in koi and feral carp in 2002[1][2].Natural infections have been documented in common carp and koi (Cyprinus carpio), goldfish, grass carp, bighead carp, zebrafish, golden shiner, and fathead minnow, among other species[1]. Because clinical signs overlap with those of other serious conditions such as koi herpesvirus (KHV), laboratory confirmation is required for diagnosis[6][5].

Cause and virology

SVC is caused by a single-stranded RNA rhabdovirus, variously named Rhabdovirus carpio, Sprivivirus cyprinus, or Carp sprivivirus in different sources[1][5][2]. It belongs to the family Rhabdoviridae[4]. The disease is historically associated with cool water, with the UF/IFAS comparison table listing an optimal temperature range of 41–64 °F (5–18 °C), markedly lower than the 64–81 °F (18–27 °C) range associated with koi herpesvirus[5].

Geographic distribution

SVC virus was first diagnosed in Yugoslavia in 1971 and is thought to have been present in Europe for decades before that[1]. It has since been identified in other European countries, Russia, Brazil, the Middle East, and China[1]. In North America, the virus was confirmed in farmed koi in North Carolina and in feral common carp in Wisconsin in 2002, with no connection established between the two cases[1][2]. Further US detections occurred in pet koi in Washington and farmed koi in Missouri in 2004, in feral common carp in the Mississippi River in Minnesota in 2007, and most recently in feral carp in Minnesota waters in 2011[1]. A 2006 outbreak was also linked to Hamilton Bay on Lake Ontario, Canada[2]. The USDA considers SVC virus a foreign animal disease in the United States, and it is not believed to be widespread, but rather limited to certain areas in wild susceptible populations[1].

Clinical signs

Clinical signs of SVC infection are often non-specific. Affected fish may appear lethargic, show decreased respiration rate, and lose equilibrium[1]. Moribund fish have been reported lying on their sides on the bottom of a tank or pond, swimming up briefly when startled before returning to the bottom, and congregating in areas of slow water flow or near pond banks[1]. According to the Southern Regional Aquaculture Center, fish infected with SVC are often lethargic, stay near the bottom, swim awkwardly, and may show exophthalmia (“pop eye”), pinpoint bleeding on the skin, a bloated abdomen, and bloody mucus from the vent[6]. Wikipedia describes additional clinical signs including external hemorrhaging, pale gills, and ascites, noting that in some cases mortality can occur without obvious clinical signs[2]. According to the US koi dealer Kodama Koi Farm, SVC is associated with hemorrhages, pale gills, and abdominal swelling[9]. Because these signs can be caused by other diseases or by poor water quality, laboratory confirmation by a diagnostician skilled in identifying viral diseases is considered essential[6].

Transmission

SVC virus can spread through direct contact, fecal material, infected water or mud, contaminated equipment, and vectors[5]. The fish louse Argulus foliaceus has been documented as a mechanical vector capable of transmitting the virus between fish[7][1]. The virus has been found in high concentrations in the liver and kidney, with lower numbers isolated from the spleen, and has been shown to persist subclinically in fish populations for up to ten weeks after experimental infection[2]. Because many aquaculture facilities keep several fish species, it is recommended that SVC-susceptible species such as koi, common carp, goldfish, grass carp, bighead carp, silver carp, and crucian carp be kept separate from non-susceptible species[1][5].

Diagnosis and treatment

Diagnosis of SVC can be accomplished by isolating the virus using fathead minnow (FHM) or epithelioma papillosum of carp (EPC) cell lines, where a susceptible virus causes the cells to degenerate and round; further tests such as polymerase chain reaction (PCR) are used to confirm the viral agent[1]. A detailed diagnostic protocol is published in the WOAH Manual of Diagnostic Tests for Aquatic Animals, chapter 2.3.9[1][10]. In the United States, samples intended to meet export requirements must be sent to a USDA-approved laboratory, and confirmation testing is completed at the USDA National Veterinary Services Laboratories in Ames, Iowa[1]. No treatment is known for SVC, according to a secondary source[8]. Efforts to prevent infection have included the development of DNA vaccines and immunostimulatory therapeutics[2], and a DNA vaccine has been shown experimentally to protect ornamental koi against North American SVC virus[1]. Diagnosis of suspected viral disease in koi generally requires evaluation by a qualified fish health laboratory or veterinarian, since clinical signs overlap with other conditions and water-quality problems[6].

Disinfection and biosecurity

SVC virus can be inactivated by a range of disinfectants and physical treatments, including 3% formalin for five minutes, sodium hypochlorite (chlorine at 540 ppm for 20 minutes), organic iodophors (200–250 ppm for 30 minutes), benzalkonium chloride (100 ppm for 20 minutes), chlorhexidine gluconate (100 ppm for 20 minutes), extreme pH (pH 3 for 3 hours or pH 12 for 10 minutes), and heating at 60 °C (140 °F) for 30 minutes, among other methods[1]. The Southern Regional Aquaculture Center lists comparable disinfection protocols specific to SVC rhabdovirus, including Virkon Aquatic at 0.5–1% for 10 minutes or 0.1% for 30 minutes and chlorine at 500 mg/L for 10 minutes[11]. Recommended farm biosecurity measures include disinfecting surface water before use (well water is considered a safer source), maintaining dedicated equipment for susceptible species, restricting access by birds, livestock, pets, and visitors, and performing routine health assessments including SVC testing on susceptible populations[1]. General biosecurity planning for koi producers should account for both SVC and koi herpesvirus (KHV) as diseases of particular concern[11].

Regulatory status and reporting

SVC is listed as a notifiable disease by the WOAH under its Aquatic Animal Health Code and Manual of Diagnostic Tests for Aquatic Animals, chapter 2.3.9[3][10][1]. It is also included on the USDA National Animal Health Reporting System National List of Reportable Animal Diseases, meaning diagnoses in wild or farmed populations in the US must be reported to USDA[1]. Within the United States, SVC is treated as a foreign or exotic disease; an accredited veterinarian or laboratory that detects it is required to notify USDA APHIS Veterinary Services, which in turn notifies the WOAH, in contrast to KHV, which is considered widespread in the US[5]. Positive detections should be reported to the Area Veterinarian in Charge (AVIC) for the state where the animals are located[1]. In Canada, SVC is a federally reportable disease, and anyone who owns or works with aquatic animals is legally required to notify the Canadian Food Inspection Agency if the disease is known or suspected[4]. Importation of SVC-susceptible species and their eggs or gametes into the US requires a USDA import permit (form VS-135) and a health certificate from the country of origin[1]. These reporting obligations are further described on the page about notifiable koi diseases and importing and exporting koi.

Common questions

Is SVC the same as koi herpesvirus (KHV)?
No. SVC is caused by an RNA rhabdovirus and is associated with cooler water (41–64 °F / 5–18 °C), while KHV is caused by a DNA herpesvirus and is associated with warmer water (64–81 °F / 18–27 °C); the two diseases have different management and regulatory implications[5].
Can SVC be treated?
No treatment is known for SVC according to a secondary source[8], though DNA vaccines and immunostimulatory therapeutics have been studied experimentally[2][1].
Do keepers have to report suspected SVC?
Yes. SVC is a notifiable disease under the WOAH and is reportable to USDA in the United States and to the Canadian Food Inspection Agency in Canada[1][3][4].
What species besides koi can get SVC?
Natural infections have been reported in common carp, goldfish, grass carp, bighead carp, zebrafish, golden shiner, and fathead minnow, among other species[1][5].
How is SVC diagnosed?
Diagnosis typically involves isolating the virus in fathead minnow or EPC cell lines followed by PCR confirmation, following protocols in the WOAH Manual of Diagnostic Tests for Aquatic Animals[1][10].

References

  1. ^ UF/IFAS EDIS VM106: Spring Viremia of Carp Virus (SVCv). University of Florida IFAS Extension (EDIS). ask.ifas.ufl.edu/publication/VM106. Retrieved November 2026.
  2. ^ Spring viraemia of carp (Wikipedia). Wikipedia. en.wikipedia.org/wiki/Spring_viraemia_of_carp. Retrieved November 2026.
  3. ^ Spring viraemia of carp - WOAH - World Organisation for Animal Health. World Organisation for Animal Health. woah.org/en/disease/spring-viraemia-of-carp/. Retrieved November 2026.
  4. ^ Spring Viraemia of Carp - inspection.canada.ca. Canadian Food Inspection Agency. inspection.canada.ca/en/animal-health/aquatic-animals/diseases/repo…. Retrieved November 2026.
  5. ^ UF/IFAS EDIS VM113: Koi Herpesvirus Disease (KHVD). University of Florida IFAS Extension (EDIS). ask.ifas.ufl.edu/publication/VM113. Retrieved November 2026.
  6. ^ SRAC Publication No. 7201: Species Profile: Koi and Goldfish. Southern Regional Aquaculture Center. srac.msstate.edu/pdfs/Fact%20Sheets/7201%20Species%20Profile-%20Koi…. Retrieved November 2026.
  7. ^ UF/IFAS EDIS FA184: Argulus (Fish Louse) Infections in Fish. University of Florida IFAS Extension (EDIS). ask.ifas.ufl.edu/publication/FA184. Retrieved November 2026.
  8. ^ Koi (Wikipedia). Wikipedia. en.wikipedia.org/wiki/Koi. Retrieved November 2026.
  9. ^ HELP, Is My Koi Sick?!? Diagnose Symptoms & Fish Diseases - FREE Health Checklist. Kodama Koi Farm (koi dealer). kodamakoifarm.com/koi-sick-health-diagnosis-symptoms-diseases/. Retrieved November 2026.
  10. ^ Manual of Diagnostic Tests for Aquatic Animals, ch. 2.3.9 Spring viraemia of carp (WOAH). World Organisation for Animal Health. woah.org/fileadmin/Home/eng/Health_standards/aahm/current/2.3.09_SV…. Retrieved November 2026.
  11. ^ SRAC Publication No. 4707: Biosecurity in Aquaculture, Part 1: An Overview. Southern Regional Aquaculture Center. srac.msstate.edu/pdfs/Fact%20Sheets/4707%20Biosecurity%20in%20Aquac…. Retrieved November 2026.