Phylogenetic Characterization of the Palyam Serogroup Orbiviruses

The Palyam serogroup orbiviruses are associated with abortion and teratogenesis in cattle and other ruminants. Of the 13 different serotypes that have been identified, the full genome sequence of only one, Kasba, has been published. We undertook to perform Next Generation Sequencing (NGS) and phylogenetic analysis on 12 Palyam serotypes plus field isolates of the African serotypes in our possession. The Palyam serogroup was found to be most closely related to the African horse sickness virus group and showed the most distant evolutionary relationship to the equine encephalosis viruses (EEV). Amino acid sequence analysis revealed that the gene encoding VP7 was the most conserved within serotypes and VP2 and VP5 showed the highest degree of variation. A high degree of sequence identity was found for isolates from the same geographical region. The phylogenetic analysis revealed two clades where the African serotypes were all very closely related in one clade and the other clade contained the Australian and Asian serotypes and one African serotype, Petevo. It was evident from the sequence data that the geographical origin of Palyam serogroup viruses played an important role in the development of the different serotypes.