碩士 / 國立臺灣大學 / 動物學研究所 / 97 / Betanodaviruses, the causative agents of viral nervous necrosis disease, are classified into 4 genotypes, including red-spotted (RG), striped jack (SJ), barfin flounder (BF) and tiger puffer (TP) nervous necrosis virus (NNV). The aim of this study is to screen NNV in the wild fish collected from different aquatic area around Taiwan, and investigated the molecular phylogeny and epidemiology of those NNV isolates. Nested RT- PCR was applied for the screening of T4 segment of coat protein gene of NNV. Both RGNNV and SJNNV were detected in the wild fish in Taiwan, and the fish of 12 species of 4 orders were first reported to be NNV host. Strong positive selection was observed in RGNNV populations from both wild-field and cultured fish, indicating that the environment preferred to keep the mutations of RGNNV. Unequal gene flow, from trash fish to the seashore fish and then to cultured fish, was monitored in RGNNV populations. It is therefore suggested that the carrier fish or sea water played a role of RGNNV reservoir and might transmit the virus from sea area to land pond. The phylogenetic tree of SJNNV revealed that all isolates from carrier fish of Taiwan were clustered into one lineage, and all isolates from diseased fish in Japan and Europe were clustered into another lineage, indicating that the distinction was not due to geographic barrier. Negative evolution was revealed in SJNNV population of cultured fish in Japan and Europe, and neutral evolution was found in SJNNV from wild-field carrier fish around Taiwan, indicating that mutation of SJNNV would reduce viral pathogenecity on cultured fish, but would not affect the fitness in wild carrier fish. It is therefore suggested the SJNNV population would be less harm than RGNNV on aquatic industry.
| Identifer | oai:union.ndltd.org:TW/097NTU05312011 |
| Date | January 2009 |
| Creators | Kun-Chan Tsai, 蔡昆展 |
| Contributors | 齊肖琪 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 94 |
Page generated in 0.0395 seconds