Spring Viremia of Carp (SVC) - FHP

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Fish Diseases

Spring Viremia of Carp (SVC)

Photo of fathead minnow

A fathead minnow experimentally infected with SVCV by intraperitoneal injection displaying clinical signs of disease. Pop-eye and external hemorrhaging on lower body cavity. Credit: USGS, Western Fisheries Research Center (Public domain.)

Spring viremia of carp virus (SVCV) is a rhabdoviral pathogen that frequently decimates common carp (Cyprinus carpio carpio) stocks throughout Europe. Carp populations in the European countries of Russia, Romania, Netherlands, Moldavia, Georgia, Germany, France, United Kingdom, and Denmark have the highest reported prevalence. In fish species that succumb to infection by SVCV, the spleen, kidney, intestines, and air bladder are typically inflamed, hemorrhaging, or swollen. Disease progression leads to necrosis of the internal organs and eventually death. Outbreaks at common carp farms in Europe normally occur in the spring, as the water temperature begins to rise after a cold winter period. The highest fish mortalities due to SVCV infection occur between 11°C and 17°C. Common carp belonging to the Cyprinidae family are the principal host species of SVCV. Natural infections of SVCV have also occurred in other cyprinid fish. Fish species from other families of Poeciliidae, Esocidae, Centrarchidae, Siluridae, and Salmonidae have also been infected by SVCV. Due to the highly infectious nature of SVCV and potential impact this virus could have on susceptible fish populations globally, any detection of SVCV requires notification within 48 hours to the Office of Internationale Epizootic (OIE), the organization charged with regulating world animal health. SVCV is one of only nine piscine viruses recognized worldwide by the OIE as a notifiable animal disease.

In April of 2002, at one of the largest koi production facilities in the United States, yearling koi in one pond began dying from SVCV. Subsequently the virus was detected in other ponds at the facility, fifteen thousand fish died from SVCV and another 135,000 fish were euthanized from ponds located both in North Carolina and Virginia. One month later in an apparently unrelated incident, dead wild carp began washing up on the shores of a Wisconsin lake. Mortalities reached 1,500 and the causative agent of the epidemic was SVCV. One year later the virus was isolated from a healthy common carp during a fish health screening in an Illinois water channel that is linked to Lake Michigan. In 2004 there were two outbreaks of SVCV, one at a private koi pond in Washington State and the other at a commercial koi hatchery in Missouri. In June 2006, SVCV was found for the first time in Canada in common carp from Lake Ontario. These fish were scheduled for shipment to France, but the virus was detected during an exportation disease screening. Later in October 2006 the United States Department of Agriculture (USDA) instituted regulations restricting the importation of live fish, fertilized eggs, and gametes of specific fish species susceptible to SVCV. Until the first outbreak in 2002, SVCV had never been reported in North America. Isolations of this exotic virus in recent years and the import restrictions placed on SVCV susceptible fish are warnings of the potential invasiveness and impact SVCV could have on vulnerable fish stocks.

Researchers at the WFRC have initiated a variety of projects to study the emergence of SVCV in North America. SVCV isolate data (e.g. genetic type, gene sequences, host species, isolation location, etc.) are being cataloged in the recently developed WFRC Fish ViroTrak database. We’ve developed a reliable challenge model to test the susceptibility of different fish host species to the North American SVCV and devised challenge treatments that induced rapid and reproducible infections in the host.

Also a novel SVCV DNA vaccine utilizing the North Carolina SVCV G-gene was designed and tested in four trial experiments in our aquatic biosafety level 3 laboratory (BSL-3). Our aquatic BSL-3 laboratory is one of only two facilities in the US designed for the testing and containment of fish pathogens that pose a high risk to the environment.