Looking back: a genetic retrospective study of Brazilian Orf virus isolates.

Orf virus (ORFV), the prototype of the genus Parapoxvirus, is the aetiological agent of contagious ecthyma (CE), a pustular dermatitis that afflicts domestic and wild small ruminants. CE is one of the most widespread poxvirus diseases in the world, causing public health impacts. Outbreaks of ORFV have been observed in all geographical regions of Brazil, affecting ovine and caprine herds. The origins, epidemiology and identity of Brazilian ORFVs are unknown, and no comparative or phylogenetic studies of these viruses have been performed. In the present study, we revisited CE outbreaks which occurred until 32 years ago, and we assessed, genetically, five viral isolates. We performed the sequencing and analysis of the three ORFV molecular markers: B2L gene, virus interferon resistance gene (VIR) and the vascular endothelial growth factor gene. Nucleotide and amino acid analysis of the analysed genes demonstrated that Brazilian ORFVs do not form a unique cluster, and presented more similarity to other worldwide ORFV samples than with each other. These data raise the questions of whether there are different worldwide ORFVs circulating in Brazil, or if all the Brazilian ORFV samples are of the same virus taken at distinct time points.