| Budget Amount *help |
¥17,680,000 (Direct Cost: ¥13,600,000、Indirect Cost: ¥4,080,000)
Fiscal Year 2022: ¥2,470,000 (Direct Cost: ¥1,900,000、Indirect Cost: ¥570,000)
Fiscal Year 2021: ¥3,510,000 (Direct Cost: ¥2,700,000、Indirect Cost: ¥810,000)
Fiscal Year 2020: ¥4,160,000 (Direct Cost: ¥3,200,000、Indirect Cost: ¥960,000)
Fiscal Year 2019: ¥7,540,000 (Direct Cost: ¥5,800,000、Indirect Cost: ¥1,740,000)
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| Outline of Final Research Achievements |
The objective of this study is to elucidate the factors behind the recent increase of virulence of infectious hematopoietic necrosis (IHN) virus. Virus isolates from dead rainbow trout fry tended to show strong virulence to the fry strain from which they were isolated, and the virus might be less sensitive to interferon of the fish strain. Many isolates from ovarian fluid of spawning fish were low virulent. Persistent virus infection was more likely to occur in infected fish with a low mortality rate and blood antibodies against the virus can be involved in suppressing the persistent infection. Adult fish were found to be re-infected with the virus just before spawning when their immunity was suppressed. These results suggests that persistent infection occurs in the juvenile fish surviving in a primary infection with low virulent virus, resulting in appearance of virus diversity in the fish during the growing up period and consequently emerging of highly virulent viruses.
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