2006 Fiscal Year Final Research Report Summary
Molecular epidemiological studies on piscine nodavirus, the causative agent of viral nervous necrosis in marine fish
| Project/Area Number |
16380132
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
General fisheries
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| Research Institution | Hiroshima University |
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Principal Investigator |
NAKAI Toshihiro Hiroshima University, Graduate School of Biosphere Science, Professor, 大学院生物圏科学研究科, 教授 (60164117)
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| Co-Investigator(Kenkyū-buntansha) |
UEMATSU Kazumasa Graduate School of Biosphere Science, Professor, 大学院生物圏科学研究科, 教授 (00116542)
OKINAKA Yasushi Graduate School of Biosphere Science, Associate Professor, 大学院生物圏科学研究科, 助教授 (80363034)
MORI Koh-ichirou Fisheries Research Agency, National Research Institute of Aquaculture, Senior Researcher, 上浦栽培漁業センター, 技術開発官 (10426314)
SUGAYA Takuma Fisheries Research Agency, National Research Institute of Aquaculture, Senior Researcher, 上浦栽培漁業センター, 技術開発官 (30426316)
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| Project Period (FY) |
2004 – 2006
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| Keywords | Betanodavirus / Nodaviridae / Viral nervous necrosis / Molecular epidemiology / Virus transmission / Reassortant virus / Disease prevention / Marine aquaculture |
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| Research Abstract |
Betanodaviruses, family Nodaviridae, are the causal agents of viral nervous necrosis (VNN) that has given severe mortality worldwide in marine aquaculture. The viruses can be classified into four types, designated SJNNV, RGNNV, TPNNV, and BFNNV, based on similarities in the coat protein gene (RNA2). We have already demonstrated that virus-carrying bloodstocks are an important inoculum source of the virus to the offspring (larvae and juveniles). However, the virus inoculum source to older fish cultured in net-pens in open sea is still unknown. Through the present research project from 2004 to 2006, we obtained many valuable epidemiological data on the virus. We first detected betanodaviruses in a variety of wild marine fish species with no clinical signs, which were obtained from aquaculture areas and showed that their RNA2 sequences were closely similar to those of RGNNV isolates identified from diseased fish. Some virus isolates were obtained using E-11 cells and all the isolates were
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highly pathogenic to sevenband grouper, one of the most susceptible fish to RGNNV. Similarly, we demonstrated that fish from non-aquaculture areas have inapparently infected with the virus, not only RGNNV but also the other types (SJNNV, BFNNV). The RNA2 sequences of these viruses had much more variations than those from diseased fish and the subclinically infected wild fish caught in aquaculture areas mentioned above. Interestingly, we failed to isolate the virus in almost all cases, suggesting the lack of virulence-determining sequences. These results suggest that genetically varied betanodaviruses in wild fish are widely spread in Pacific, Japan Sea, and East-China Sea. Pelagic, highly migratory and mass-caught fish such as Japanese jack mackerel is possibly an effective vector to transmit betanodaviruses to geographically remote area, and might play an important role for the epidemic of VNN among cultured and also wild fish populations. We also developed some methods to prevent the disease through this project. Less
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