Genetic analysis of fish iridoviruses isolated in Taiwan during 2001–2009

Abstract

To investigate the genetic relationships between field strains of iridoviruses gathered from various fish species in Taiwan, viruses that were collected from 2001 to 2009 were analyzed. Open reading frames encoding the viral major capsid protein (MCP) and adenosine triphosphatase (ATPase) were sequenced for phylogenetic analysis. Our results indicated that iridoviruses from Taiwan aquaculture fishes could be classified into two groups: prior to 2005, the viruses were closely related to members of the genus Ranavirus; and after 2005, they were similar to members of the genus Megalocytivirus. Based on the analysis of MCP amino acid sequences, virus isolates were divided into 4 major genotypes that were related to ISKNV, RSIV, FLIV, and GIV, respectively. Pairwise comparisons of MCP genes showed that the ranavirus was an epidemic pathogen for economically important species in the major production regions and cultured marine fish, while the megalocytivirus isolates were sensitive to host range. In addition, the distribution of synonymous and non-synonymous changes in the MCP gene revealed that the iridoviruses were evolving slowly, and most of the variations were synonymous mutations. The Ka/Ks values were lower than one, and hence, the viruses were under negative selection.

Detection of infectious spleen and kidney necrosis virus (ISKNV) and turbot reddish body iridovirus (TRBIV) from archival ornamental fish samples

“…This accession was obtained from barred knifejaw (rock bream) fingerlings from a disease outbreak in Taiwan during 2008 that had been recently imported as larvae from Korea. The barred knifejaw isolate exhibited the greatest similarity to the TRBIV megalocytivirus isolates, in contrast to all other isolates characterised during the same study (Huang et al 2011).…”

“…However, all 3 forms of 'grouper iridovirus' (i.e. ISKNV megalocytivirus, RSIV megalocytivirus and ranavirus) have been documented from Taiwan (Huang et al 2011), and no details were provided by Chao et al (2004) to establish how megalocytiviral infection was confirmed, or which genotype was responsible, or whether a megalocytivirus was in volved at all. Consequently, the situation in 1980 is ambiguous and cannot be confirmed as the megalocytivirus index case.…”

“…2 & 3). Given that RBIV/Tp/45/08 was considered by Huang et al (2011) to be TRBIV-like, this convention will also be followed here and this clade will be regarded as a subgroup of the TRBIV genotype, and designated as Clade 2 (Figs. 2 & 3).…”

Isolation of a Ranavirus-type grouper iridovirus in mainland China and comparison of its pathogenicity with that of a Megalocytivirus-type grouper iridovirus

“…Coldblooded vertebrate viruses, including the genera Lymphocystivirus, Ranavirus, and Megalocytivirus, are collectively called piscine iridoviruses because they are important causative agents of bony fish diseases (Kurita and Nakajima, 2012;Li et al, 2014). Furthermore, Ranavirus and Megalocytivirus are commonly associated with viral diseases of numerous kinds of groupers (Huang et al, 2011;Lü et al, 2005;Tsai et al, 2005). Thus, grouper iridovirus (GIV) mainly includes two different genera, namely, Ranavirus and Megalocytivirus, which belong to Iridoviridae.…”

Establishment and Characterization of a Novel Kidney-cell Line from Orange-spotted Grouper, Epinephelus coioides, and its Susceptibility to Grouper Iridovirus

“…Developing an ideal cell line for in vitro studies of cell-virus interactions, virus propagation, isolation and vaccine development is critical to disease control in aquaculture. Taiwanese iridovirus isolates consist of three major genotypes : grouper iridovirus (GIV) which belong to Ranavirus, red sea bream iridovirus (RSIV), and infectious spleen and kidney necrosis virus (ISKNV) that are classified to Megalocystivirus genuses [7]. Hence, development a continuous cell line from tropical fish species for identifying pathogenesis of viral diseases and for vaccine production is imperative.…”