Megalocytiviruses

The genus Megalocytivirus, represented by red sea bream iridovirus (RSIV), the first identified and one of the best characterized megalocytiviruses, Infectious spleen and kidney necrosis virus (ISKNV), the type species of the genus, and numerous other isolates, is the newest genus within the family...

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Bibliographic Details
Published in:Viruses
Main Authors: Kazuhiro Nakajima, Jun Kurita
Format: Article in Journal/Newspaper
Language:English
Published: MDPI AG 2012
Subjects:
Online Access:https://doi.org/10.3390/v4040521
https://doaj.org/article/0f62db4268a14e3c83f54fd4c576ff1c
Description
Summary:The genus Megalocytivirus, represented by red sea bream iridovirus (RSIV), the first identified and one of the best characterized megalocytiviruses, Infectious spleen and kidney necrosis virus (ISKNV), the type species of the genus, and numerous other isolates, is the newest genus within the family Iridoviridae. Viruses within this genus are causative agents of severe disease accompanied by high mortality in multiple species of marine and freshwater fish. To date outbreaks of megalocytivirus-induced disease have occurred primarily in south-east Asia and Japan, but infections have been detected in Australia and North America following the importation of infected ornamental fish. The first outbreak of megalocytiviral disease was recorded in cultured red sea bream (Pagrus major) in Japan in 1990 and was designated red sea bream iridovirus disease (RSIVD). Following infection fish became lethargic and exhibited severe anemia, petechiae of the gills, and enlargement of the spleen. Although RSIV was identified as an iridovirus, sequence analyses of RSIV genes revealed that the virus did not belong to any of the four known genera within the family Iridoviridae. Thus a new, fifth genus was established and designated Megalocytivirus to reflect the characteristic presence of enlarged basophilic cells within infected organs. Indirect immunofluorescence tests employing recently generated monoclonal antibodies and PCR assays are currently used in the rapid diagnosis of RSIVD. For disease control, a formalin-killed vaccine was developed and is now commercially available in Japan for several fish species. Following the identification of RSIV, markedly similar viruses such as infectious spleen and kidney necrosis virus (ISKNV), dwarf gourami iridovirus (DGIV), turbot reddish body iridovirus (TRBIV), Taiwan grouper iridovirus (TGIV), and rock bream iridovirus (RBIV) were isolated in East and Southeast Asia. Phylogenetic analyses of the major capsid protein (MCP) and ATPase genes indicated that although these viruses shared ...