Molecular evolution of American field strains of bluetongue and epizootic haemorrhagic disease viruses.

Recent Orbivirus occurrences in the Americas have been investigated using whole genome amplification and sequencing followed by phylogenetic analysis. The Bluetongue virus (BTV) and Epizootic haemorrhagic disease virus (EHDV) whole genomes were amplified without prior sequence knowledge and deep sequenced. This technology was applied to evaluate BTV-3 isolates spanning 4 decades from Florida, Arkansas, Mississippi, South Dakota, Central America, and the Caribbean Basin. The results of the dataset analysis are consistent with the hypothesis that these viruses were introduced into the United States from Central America and the Caribbean Basin. A similar analysis has been performed on a recent BTV-2 isolate from California. It indicates that the BTV-2 strain was likely introduced into Florida and then moved South to the Caribbean and West to California. A historical (1955-2012) molecular characterisation of EHDV strains was also completed, and subsequently used as reference sequence for comparison of genomes from recent 2012 cattle isolates associated with clinical disease. Finally, this analysis was performed on BTV-11 isolated from 2 canine cases and demonstrated that the genome sequences of the virus isolates from these cases were almost identical. These studies indicate the value of this technology in understanding virus epidemiology and ecology.