Molecular epidemiology of white spot syndrome virus within Vietnam.
White spot syndrome virus (WSSV), the sole member of the virus family Nimaviridae, is a large double-stranded DNA virus that infects shrimp and other crustaceans. By alignment of three completely sequenced isolates originating from Taiwan (WSSV-TW), China (WSSV-CN) and Thailand (WSSV-TH), the variable loci in the genome were mapped. The variation suggests the spread of WSSV from a common ancestor originating from either side of the Taiwan Strait to Thailand, but support for this hypothesis through analysis of geographical intermediates is sought. RFLP analysis of eight Vietnamese WSSV isolates, of which six were collected along the central coast (VN-central) and two along the south coast (VN-south), showed apparent sequence variation in the variable loci identified previously. These loci were characterized in detail by PCR amplification, cloning and sequencing. Relative to WSSV-TW, all VN-central isolates showed a approximately 8.5 kb deletion in the major variable region ORF23/24, whereas the VN-south isolates contain a deletion of approximately 11.5 or approximately 12.2 kb, compared to a approximately 1.2 or approximately 13.2 kb deletion in WSSV-CN and WSSV-TH, respectively. The minor variable region ORF14/15 showed deletions of various sizes compared with WSSV-TH for all eight VN isolates. The data suggest that the VN isolates and WSSV-TH have a common lineage, which branched off from WSSV-TW and WSSV-CN early on, and that WSSV entered Vietnam by multiple introductions. A model is presented for the spread of WSSV from either side of the Taiwan Strait into Vietnam based on the gradually increasing deletions of both 'variable regions'. The number and order of repeat units within ORF75 and ORF125 appeared to be suitable markers to study regional spread of WSSV.
Dieu
Bui Thi Minh
BTM
Laboratory of Virology, Wageningen University, Binnenhaven 11, 6709 PD Wageningen, The Netherlands.|Biotechnological Research and Development Institute, Can Tho University, 3/2 Street Nr 1, 008471 Can Tho City, Vietnam.
Marks
Hendrik
H
Laboratory of Virology, Wageningen University, Binnenhaven 11, 6709 PD Wageningen, The Netherlands.
Siebenga
J Joukje
JJ
Laboratory of Virology, Wageningen University, Binnenhaven 11, 6709 PD Wageningen, The Netherlands.
Goldbach
Rob W
RW
Laboratory of Virology, Wageningen University, Binnenhaven 11, 6709 PD Wageningen, The Netherlands.
Zuidema
Douwe
D
Laboratory of Virology, Wageningen University, Binnenhaven 11, 6709 PD Wageningen, The Netherlands.
Duong
Tran Phuoc
TP
Biotechnological Research and Development Institute, Can Tho University, 3/2 Street Nr 1, 008471 Can Tho City, Vietnam.
Vlak
Just M
JM
Laboratory of Virology, Wageningen University, Binnenhaven 11, 6709 PD Wageningen, The Netherlands.
D000818:Animals; D004259:DNA-Directed DNA Polymerase / Q000235:genetics; D014644:Genetic Variation; D018598:Minisatellite Repeats; D016366:Open Reading Frames; D033561:Penaeidae / Q000821:virology*; D046848:White spot syndrome virus 1 / Q000235:genetics*
D004259:DNA-Directed DNA Polymerase