Susceptibility of marine fish species to a megalocytivirus, turbot iridovirus, isolated from turbot, Psetta maximus (L.)

Abstract

Turbot iridovirus (TBIV), a member of the genus Megalocytivirus in the family Iridoviridae, was isolated from diseased turbot, Psetta maximus (L.), in Korea in 2003. In this study, experimental infection of turbot, Japanese flounder, Paralichthys olivaceus (Temminck & Schlegel), and rock bream, Oplegnathus fasciatus (Temminck & Schlegel), with TBIV was performed to evaluate the viral susceptibility of these fish species. After virus exposure, the mortalities of turbot reared at 22 and 25 degrees C were 60% and 100%, respectively, suggesting that TBIV is the causative agent of the mass mortality of turbot that occurred in Korea in 2003. Moreover, TBIV was detected in Japanese flounder and rock bream by polymerase chain reaction after experimental infection (26 days post-inoculation) despite no viral pathogenicity in these fish, suggesting that these two fish species are also susceptible to the virus. It is possible that horizontal transmission of TBIV occurs among these three fish species because turbot is routinely cultured with Japanese flounder and rock bream in Korea.

Megalocytivirus infection in fish

“…2002). TBIV showed high pathogenicity in turbot compared with rock bream [ Oplegnathus fasciatus (Temminck & Schlegel 1844)] and Japanese flounder (Oh et al. 2006).…”

“…The rate of replication of Megalocytivirus varies with temperature. At temperatures between 20 and 25°C, members of this genus replicate well both in vivo and in vitro (Oh et al. 2006).…”

Genetic variation and geographic distribution of megalocytiviruses

“…Kawakami and Nakajima (2002) reported that the disease caused by a megalocytivirus, termed red seabream iridovirus (RSIV), occurred in 31 cultured fish species (included within orders Perciformes, Pleuronectiformes, and Tetraodontiformes) in Japan. In a recent study, we also isolated a new megalocytivirus, turbot iridovirus (TBIV), from diseased turbot Scophthalmus maximus in Korea, indicating that megalocytiviruses have a broad host range (Kim et al, 2005;Oh et al, 2006). The viral genome of four megalocytiviruses, RSIV (Ehime-1 strain), ISKNV, rock bream iridovirus (RBIV) isolated from rock bream Oplegnathus fasciatus, and orange-spotted grouper iridovirus (OSGIV) isolated from orange-spotted grouper Epinephelus coioides have been completely sequenced (He et al, 2001;Kurita et al, 2002;Do et al, 2004;Lü et al, 2005).…”

Prevalence of red sea bream iridovirus among organs of Japanese amberjack (Seriola quinqueradiata) exposed to cultured red sea bream iridovirus

“…or i.m. injections of the homogenate from the organs of diseased fish or isolated viruses were used as the inocula in most reports (Chou et al, 1998;He et al, 2002;Jeong et al, 2006Jeong et al, , 2008aJun et al, 2009;Kim et al, 2012;Nakajima et al, 1997;Oh et al, 2006;Oshima et al, 1998). Thus, there is minimal information on the virus kinetics of fish after virus infection by immersion, which is known to closely approximate the natural infection conditions.…”