TAILIEUCHUNG - Báo cáo y học: " Molecular epidemiology of salmonid alphavirus (SAV) subtype 3 in Norway"

Molecular epidemiology of salmonid alphavirus (SAV) subtype 3 in Norway | Jansen et al. Virology Journal 2010 7 188 http content 7 1 188 VIROLOGY JOURNAL RESEARCH Open Access Molecular epidemiology of salmonid alphavirus SAV subtype 3 in Norway Mona D Jansen 1 Britt Gjerset2 Ingebjorg Modahl2 Jon Bohlin1 Abstract Background Pancreas disease PD is a viral fish disease which in recent years has significantly affected Norwegian salmonid aquaculture. In Norway the aetiological agent salmonid alphavirus SAV has been found to be represented by the subtype 3 only. SAV subtype 3 has in previous analyses been found to show a lower genetic divergence than the subtypes found to cause PD in Ireland and Scotland. The aim of this study was to evaluate the nucleotide nt and amino acid divergence and the phylogenetic relationship of 33 recent SAV subtype 3 sequences. The samples from which the sequences were obtained originated from both PD endemic and nonendemic regions in an attempt to investigate agent origin spread. Multiple samples throughout the seawater production phase from several salmonid populations were included to investigate genetic variation during an outbreak. The analyses were mainly based on partial sequences from the E2 gene. For some samples additional partial 6 K and nsP3 gene sequences were available. Results The nucleotide divergence for all gene fragments ranged from total identity divergence to 1103 nt fragment of E2 451 nt fragment of E2 6 K and nsP3 . This low nucleotide divergence corresponded well to previous reports on SAV 3 sequences however the observed divergence for the short E2 fragment was higher than that previously reported. When compared to SAVH20 03 AY604235 amino acid substitutions were detected in all assessed gene fragments however the in vivo significance of these on for example disease outbreak mortality could not be concluded on. The phylogenetic tree based on the 451 nt E2 fragment showed that the sequences divided into two clusters with low genetic divergence .

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