title: Full-Genome Sequencing and Confirmation of the Causative Agent of Erythrocytic Inclusion Body Syndrome in Coho Salmon Identifies a New Type of Piscine Orthoreovirus.
abstract: Erythrocytic inclusion body syndrome (EIBS) causes mass mortality in farmed salmonid fish, including the coho salmon, Onchorhynchus kisutchi, and chinook salmon, O. tshawytscha. The causative agent of the disease is a virus with an icosahedral virion structure, but this virus has not been characterized at the molecular level. In this study, we sequenced the genome of a virus purified from EIBS-affected coho salmon. The virus has 10 dsRNA genomic segments (L1, L2, L3, M1, M2, M3, S1, S2, S3, and S4), which closely resembles the genomic organization of piscine orthoreovirus (PRV), the causative agent of heart and skeletal inflammation (HSMI) in Atlantic salmon and HSMI-like disease in coho salmon. The genomic segments of the novel virus contain at least 10 open reading frames (ORFs): lambda 1 (λ1), λ2, λ3, mu 1 (μ1), μ2, μNS, sigma 1 (σ1), σ2, σ3, and σNS. An additional ORF encoding a 12.6-kDa protein (homologue of PRV p13) occurs in the same genomic segment as σ3. Phylogenetic analyses based on S1 and λ3 suggest that this novel virus is closely related to PRV, but distinctly different. Therefore, we designated the new virus 'piscine orthoreovirus 2' (PRV-2). Reverse transcription-quantitative real-time PCR revealed a significant increase in PRV-2 RNA in fish blood after the artificial infection of EIBS-naïve fish but not in that of fish that had recovered from EIBS. The degree of anemia in each fish increased as the PRV-2 RNA increased during an epizootic season of EIBS on an inland coho salmon farm. These results indicate that PRV-2 is the probable causative agent of EIBS in coho salmon, and that the host acquires immunity to reinfection with this virus. Further research is required to determine the host range of PRV species and the relationship between EIBS and HSMI in salmonid fish.
authors: Research Center of Fish Diseases, National Research Institute of Aquaculture, Japan Fisheries Research and Education Agency, Minami-Ise, Mie, Japan.
authors: Tomokazu
authors: T
authors: Takano
authors: Miyagi Prefecture Fisheries Technology Institute, Ishinomaki, Miyagi, Japan.
authors: Akatsuki
authors: A
authors: Nawata
authors: Research Center of Fish Diseases, National Research Institute of Aquaculture, Japan Fisheries Research and Education Agency, Minami-Ise, Mie, Japan.
authors: Takamitsu
authors: T
authors: Sakai
authors: Research Center of Fish Diseases, National Research Institute of Aquaculture, Japan Fisheries Research and Education Agency, Minami-Ise, Mie, Japan.
authors: Tomomasa
authors: T
authors: Matsuyama
authors: Research Center of Fish Diseases, National Research Institute of Aquaculture, Japan Fisheries Research and Education Agency, Minami-Ise, Mie, Japan.
authors: Takafumi
authors: T
authors: Ito
authors: Research Center of Fish Diseases, National Research Institute of Aquaculture, Japan Fisheries Research and Education Agency, Minami-Ise, Mie, Japan.
authors: Jun
authors: J
authors: Kurita
authors: Research Center of Fish Diseases, National Research Institute of Aquaculture, Japan Fisheries Research and Education Agency, Minami-Ise, Mie, Japan.
authors: Sachiko
authors: S
authors: Terashima
authors: Research Center for Bioinformatics and Biosciences, National Research Institute of Fisheries Science, Japan Fisheries Research and Education Agency, Yokohama, Kanagawa, Japan.
authors: Motoshige
authors: M
authors: Yasuike
authors: Research Center for Bioinformatics and Biosciences, National Research Institute of Fisheries Science, Japan Fisheries Research and Education Agency, Yokohama, Kanagawa, Japan.
authors: Yoji
authors: Y
authors: Nakamura
authors: Research Center for Bioinformatics and Biosciences, National Research Institute of Fisheries Science, Japan Fisheries Research and Education Agency, Yokohama, Kanagawa, Japan.
authors: Atushi
authors: A
authors: Fujiwara
authors: Miyagi Prefecture Fisheries Technology Institute, Ishinomaki, Miyagi, Japan.
authors: Akira
authors: A
authors: Kumagai
authors: Research Center of Fish Diseases, National Research Institute of Aquaculture, Japan Fisheries Research and Education Agency, Minami-Ise, Mie, Japan.
authors: Chihaya
authors: C
authors: Nakayasu
mesh_terms: D000818:Animals; D005393:Fish Diseases / Q000821:virology*; D023281:Genomics; D017683:Oncorhynchus / Q000097:blood / Q000821:virology*; D018165:Orthoreovirus / Q000235:genetics* / Q000502:physiology*; D012367:RNA, Viral / Q000235:genetics
chemical_list: D012367:RNA, Viral