Susceptibility of Koi Carp, Common Carp, Goldfish, and Goldfish × Common Carp Hybrids to Cyprinid Herpesvirus-2 and Herpesvirus-3

Hybrid goldfish (male goldfish Carassius auratus × female common carp Cyprinus carpio) were completely resistant to mortality following experimental infections with cyprinid herpesvirus-2 (CyHV-2) and moderately resistant to cyprinid herpesvirus-3 (CyHV-3). In contrast, examination of the parental species demonstrated that goldfish were highly susceptible to CyHV-2 infections and that both common carp and koi (a variant of common carp) were highly susceptible to CyHV-3. Approximately 50% of the hybrids examined at 25 d after intraperitoneal injection with either CyHV-2 or CyHV-3 possessed viral genomic DNA, as detected by polymerase chain reaction assays. These initial trials suggest that hybrid goldfish have a natural resistance to mortality following experimental challenge with CyHV-2 and CyHV-3. However, additional studies that examine virus replication, including the potential for the development of a carrier state in hybrids, are needed. The production of hybrids for the food fish market may represent one means of avoiding the severe and negative impacts of the disease associated with CyHV-3.