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viral

Spring viremia of carp (SVC / Rhabdovirus carpio)

A notifiable viral hemorrhagic disease affecting cyprinids (koi, goldfish, carp) primarily in spring at water temperatures of 11–17°C (52–63°F). Causes hemorrhaging, abdominal swelling, protruding eyes, and mass mortality. SVC is a regulated disease in many countries suspected outbreaks must be reported to animal health authorities.

Urgentrequires professional diagnosis2 source notes

Do first

  • Do NOT move fish to other systems. SVC is highly contagious and a notifiable disease.
  • Contact a fish veterinarian or local animal health authority immediately if SVC is suspected.
  • Isolate the affected system completely.
  • Euthanize moribund fish humanely.
  • Do not share water, equipment, or fish from the affected system with other ponds or tanks.

Escalate if

  • Mass mortality in cyprinids in cool spring weather: report immediately.
  • Any confirmed or strongly suspected SVC diagnosis: authorities must be notified.
  • Multiple separate ponds or systems affected: indicates environmental spread.

Water clues

These readings can push this pattern higher or lower in the triage result.

temp below species min+4

SVC is most active in spring at 11–17°C. Cold-weather fish mortality in cyprinids raises suspicion.

Care protocol

Follow only the steps that fit your species, tank inhabitants, and medication label.

SVC suspicion criteria

  1. SVC primarily affects koi, common carp, and goldfish in spring (water temperature 11–17°C).
  2. Multiple fish affected simultaneously with hemorrhaging, swelling, and eye protrusion.
  3. Definitive diagnosis requires PCR or virus isolation from a veterinary diagnostic laboratory.
  4. Send a freshly dead fish (chilled but not frozen) to a certified laboratory.
  5. Do not attempt hobby-level treatment while awaiting diagnosis. Focus on biosecurity.
Cautions
  • SVC symptoms overlap with many bacterial and other viral diseases. Professional diagnosis is required.
  • False assumption that an outbreak is SVC can cause unnecessary destruction of healthy stock. Confirm with testing.

Legal and biosecurity obligations

  1. In the USA, SVC is reportable to state veterinarians and USDA APHIS. Contact them promptly.
  2. In the EU and UK, SVC is a listed disease. Follow national reporting requirements.
  3. Cooperate fully with any disease investigation by authorities.
  4. Document the timeline of the outbreak and any recent fish movements or water source changes.
  5. After confirmed SVC: the infected system must be depopulated and disinfected before restocking.
Cautions
  • Failure to report SVC may result in legal consequences in some jurisdictions.
  • The virus can survive for weeks in water and on equipment. Thorough disinfection is mandatory.

Source notes

References and context notes used for this triage entry.

Spring Viremia of Carp USDA APHISUSDA APHIS reference for SVC as a regulated disease in the United States.SVC World Organisation for Animal Health (WOAH)International reference for SVC listing status and reporting requirements.
Run Symptom CheckerCompare this pattern against water readings, affected count, and recent tank context.Ask AdvisorUse TankFlare Advisor to review this against your saved tank and recent logs.

Related patterns

Similar symptoms or risk factors worth comparing before treatment.

UrgentKoi herpesvirus (KHV / Cyprinid herpesvirus 3)

A highly contagious and often fatal viral disease affecting koi (Cyprinus carpio) and common carp. Causes gill damage, lethargy, sunken eyes, and mass mortality typically at water temperatures between 16–25°C (60–77°F). A notifiable disease in many countries. There is no cure; management focuses on biosecurity and welfare decisions.

UrgentUronema marinum (marine ciliate)

A scavenger ciliate that becomes pathogenic under poor water quality or stress, causing rapidly spreading open lesions, internal hemorrhaging, and fast death in marine fish. Fish appear to melt. Uronema is most dangerous to thin-bodied fish (chromis, small wrasses, clownfish) and is often introduced with uncleaned live rock or wild-caught fish. Notoriously difficult to treat.

UrgentBrooklynella hostilis (clownfish disease)

A rapidly progressing skin ciliate that preferentially attacks clownfish (Amphiprion spp.) but can infect other marine fish. Causes excessive mucus, sloughing skin, rapid breathing, and fast deterioration. Often fatal within 24–48 hours without treatment. Can be confused with marine velvet but has a distinct slimy, sloughing appearance.

UrgentBacterial septicemia (hemorrhagic septicemia)

Red streaking, hemorrhaging under the skin, and systemic illness caused by gram-negative bacteria (most commonly Aeromonas hydrophila) entering the bloodstream. Can follow injury, fin rot, poor water quality, or be primary in severely stressed fish. A systemic emergency.