Whole‐genome analysis of red sea bream iridovirus spread in 2021 in Japan provided epidemiological and viral traits insight

Abstract

Red sea bream iridovirus (RSIV) is the pathogen that causes red sea bream iridoviral disease. It causes a huge loss to the Japanese aquaculture industry. In 2021, outbreaks of red sea bream iridovirus occurred in South Japan. This study analysed nine whole‐genome sequences of RSIV isolated in Oita and Ehime Prefectures in 2021 using a short‐read next‐generation sequencer. Nine isolates had highly uniform sequences, and there was no variant depending on locations or host species. Phylogenetic analyses with other reported megalocytivirus isolates showed that RSIV isolated in 2021 was genetically different from RSIV previously isolated in Oita and Ehime Prefectures in 2017–2019. These results suggest that RSIV isolated in Oita and Ehime Prefectures in 2021 might spread from a common ancestor different from the recent one. Additionally, it was found that RSIV isolated in 2021 had sequence mutations on protein‐coding sequences that may be involved in viral pathogenicity and infectivity.

The Inactivated ISKNV-I Vaccine Confers Highly Effective Cross-Protection against Epidemic RSIV-I and RSIV-II from Cultured Spotted Sea Bass Lateolabrax maculatus

“…The results showed that the genomes of SBIV-VP13 and SBIV-V12 are composed of 112,158 bp and 111,876 bp and encode 119 and 118 putative ORFs, respectively. The GC content of both genomes is 53%, which is highly consistent with those of several other sequenced ISKNV, RSIV, RBIV, orange-spotted grouper iridovirus (OSGIV), and large yellow croaker iridovirus (LYCIV) isolates ( 12 – 14 , 38 , 39 ).…”

“…Generally, members in ISKNV species, regardless of genotype, have GC content ranging from 53% to 55% and similar genomic sizes of 110,104 bp to 112,636 bp. The general genomic identities among ISKNV species are shared from 93% to 98% ( 12 – 14 ). In contrast, SDDV has a larger genome size (>130 kb) but a much lower genomic identity than ISKNV species ( 9 , 10 , 15 ).…”