Susceptibility of Japanese Cyprininae fish species to cyprinid herpesvirus 2 (CyHV-2).

Cyprinid herpesvirus 2 (CyHV-2) is known as the causative agent of herpesviral haematopoietic necrosis (HVHN) of goldfish (Carassius auratus). Recently, the virus has also been detected from Prussian carp (C. gibelio) and crucian carp (C. carassius) from European and Asian countries. To analyze the risk of spreading to new host species, the susceptibility of other fish species to the virus is essential. In this study experimental infections of indigenous Cyprininae species in Japan were performed by immersion in and intraperitoneal injection of a CyHV-2 isolate. Although Edonishiki, a variety of goldfish, immersed with the virus showed a cumulative mortality of 90%, no mortality was observed in ginbuna C. auratus langsdorfii, nagabuna C. auratus buergeri, nigorobuna C. auratus grandoculis and common carp Cyprinus carpio. Cumulative mortality was 100, 20 and 10% in intraperitoneally injected Edonishiki, ginbuna and nagabuna, respectively. Furthermore all Edonishiki immersed with the virus died. However, even after stimuli of sudden temperature changes, the immersed ginbuna and nagabuna did not die. Moreover no mortality was observed in co-reared Ranchu, another variety of goldfish, with immersed ginbuna and nagabuna although all three Ranchu co-reared with immersed Edonishiki died. CyHV-2 DNA was detected and the virus was re-isolated from all dead fish. Moreover CyHV-2 DNA was detected from some of the surviving Carassius spp. These results revealed that susceptibility of Japanese indigenous Cyprininae fish species to CyHV-2 is much lower than for goldfish. In addition, ability of replication of CyHV-2 might be different among Carassius fish species.