Spring Viraemia of carp (SVC) is a contagious and potentially fatal viral disease affecting fish. As its name implies, SVC may be seen in carp in the spring time. However, SVC may also be seen in other seasons (especially in the fall) and in other fish species including goldfish and the European wells catfish. Until recently, SVC had only been reported in Europe and the Middle East. The first cases of SVC reported in the United States were in Spring 2002 in cultivated ornamental common carp (Koi) and wild common carp. The number of North American fish species susceptible to SVC is not yet known.
What Species are Susceptible to Spring Viraemia of Carp virus?
The following fish are susceptible to Spring Viraemia: the common carp (Cyprinus carpio), grass carp (Ctenopharyngodon idellus), silver carp (Hypophthalmichthys molotrix), bighead carp (Aristichthys nobilis), crucian carp (Carassius carassius), goldfish (Carassius auratus), tench (Tinca tinca), and sheatfish (Silurus glanis). The Cyprinid fishes are produced as food fish, ornamental fish (koi and goldfish) and baitfish. In 1998 in the US, 39 facilities produced food carp, 115 produced koi, 65 produced ornamental goldfish, and 34 produced feeder goldfish. The total value of farm sales was $21.2 million. The US exported $1.8 million worth of live carp in 2001, almost exclusively to Canada.
Signs of SVC in Fish
The first signs of SVC disease in fish may be a change in behavior. The diseased fish may breathe and move more slowly, form groups in slow–flowing water near the pond bank, and lie on their side at the pond bottom. On the outside of a fish with SVC, the skin and gills may appear dark red, the eyes may bulge outward, the belly may be swollen, and bloody mucus may hang from the vent. On the inside of a fish with SVC, a lot of fluid may be in the belly cavity and internal organs, blood in the swim bladder, and reddening and swelling of the gut. However, not all fish showing these signs necessarily have SVC, as these same signs may also be seen in many other diseases. Those fish that don't die from SVC may recover and appear healthy, but these fish actually may remain infected with the SVC virus and continue to shed and spread the virus to other fish. Because the SVC virus may remain hidden in infected fish, the disease is difficult to eliminate from a site. Diagnosis of the SVC virus in fish can be confirmed through virus isolation and other sophisticated diagnostic tests done by an approved laboratory.
SVC Spread and Control
The spread of SVC may occur through contact with water contaminated with the infected fish's feces, urine, or mucus. The virus may be spread through contaminated equipment, fish parasites, predatory birds, and on the outside of an infected fish's eggs. Once SVC is established at a site, it may be difficult to eradicate because of virus–infected carrier fish. It may be necessary to destroy all aquatic life in a pond to eliminate the disease from the site.
Although complete eradication is difficult, SVC can likely be controlled and contained within high–risk zones through surveillance and better management practices, including strict biosecurity procedures. People may transmit the virus with them from place to place on their clothing, footwear, equipment, etc, but the virus does not cause disease in humans. There has never been a single report of humans being infected with the SVC virus either from contact or from eating an infected fish.
SVC Prevention Information for Koi Keepers
Hobbyists who actively transport and show their fish in organized competitive Koi shows should only show their fish in English–style shows. In English–style shows, each participant's Koi are kept in separate show tanks. From a disease transmission viewpoint, most aquatic animal health professionals recommend the English–style shows. Good biosecurity measures (e.g., avoidance or disinfection of any potentially infected, shared equipment) while at a show is highly recommended and will also protect fish from infection by the highly contagious Koi herpes virus and other communicable diseases. The best way to prevent an outbreak of SVC in a pond is QUARANTINE. Quarantine is the #1 proven method to stop the spread of disease. New Koi should be quarantined for a minimum of 3 weeks at 75 degrees Fahrenheit before they can be released into the general population.
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