First Report of Spring Viremia of Carp Virus (SVCV) in Wild Common Carp in North America

Abstract

In spring 2002, an estimated 1,500 common carp Cyprinus carpio in Cedar Lake, northwestern Wisconsin, died over a 6-week period from late April through the first week in June. Three moribund carp were necropsied and had signs consistent with spring viremia of carp (SVC) disease, including petechiae and ecchymotic hemorrhages on the skin, ascites, and edematous kidney and spleen. A virus was isolated on fathead minnow cells and shown to be a rhabdovirus by electron microscopy. Immunoassay results indicated a close serological relationship with spring viremia of carp virus (SVCV). This was confirmed by a reverse transcriptase–polymerase chain reaction assay and subsequent analysis of a subsection glycoprotein gene. Immunocytochemistry and serum neutralization tests indicated that the Cedar Lake isolate did not share complete antigenic identity with the European reference SVCV. Also, the isolate showed an inhibition of cytopathic effect after repeated subculture in epithelioma papulosum cyprini and bluegill fibroblast cells when compared with other SVCV isolates. In virus transmission studies the isolate was shown to be of low virulence for juvenile carp. Sequence analysis showed that the Cedar Lake SVCV isolate was more closely related to a recently isolated North Carolina strain of SVCV (98.6% nucleotide identity) and to strains of Asian origin rather than the European reference strain of SVCV. This is the first report of an SVC epizootic in a wild common carp population in North America.