Taura syndrome virus (TSV) is an important virus infecting penaeid shrimp in the western hemisphere. Genetic variation and immunohistochemical differences of 20 TSV isolates collected from the USA, Taiwan, Mexico and Nicaragua were compared. Capsid protein genes CP1 (546 bp) and CP2 (584 bp) were amplified by RT-PCR and the cDNAs were sequenced. Pairwise comparison of nucleotide sequences showed a 0-2.4% difference in CP1 and a 0-3.5 % difference in CP2. Phylogenetic analyses clustered the TSV isolates into two groups: one contained USA, Taiwan and some Mexican isolates, the other contained Mexican isolates only. Immunohistochemical analysis using a TSV-specific monoclonal antibody produced positive results for the USA and Taiwan isolates but negative results for the Mexican and Nicaraguan isolates. Molecular and immunohistochemical data suggest the existence of at least two TSV strains, one of which might have evolved following contact with a new penaeid host, Penaeus stylirostris.
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