Identification and phylogenetic analysis of an Orf virus isolated from an outbreak in sheep in the Jilin province of China

Abstract

This study investigated an acute outbreak of contagious ecthyma dermatitis that occurred in November 2008 in a herd of 180 small-tailed Han sheep in the Jilin province of China. The pathological findings of this case revealed severe vascular proliferation, viral cytopathic changes in keratinocytes by vacuolar degeneration, ballooning degeneration, and eosinophilic cytoplasmic inclusions, suggesting that the disease could have been caused by an Orf virus (ORFV) infection. Immunohistochemistry, indirect immunofluorescence (IFA), and transmission electron microscopy supported the diagnosis of ORFV infection. Finally, the pathogen of the disease was identified using polymerase chain reaction (PCR) and sequences of major envelope protein genes (ORFV 011(B2L) and ORFV 059(F1L)). The full-length ORFV 011(B2L) and ORFV 059(F1L) genes were cloned and sequenced. The nucleotide and amino acid sequences of ORFV 011(B2L) and ORFV 059(F1L) genes in these outbreaks were analyzed, and their phylogenetic trees were constructed. The phylogenetic studies of ORFV 011(B2L) genes and ORFV 059(F1L) genes showed that the ORFV-Jilin province isolate clustered in different branches and was closer to the ORFV-Mukteswar 67/04 isolate and the ORFV-OV/C2 isolate, respectively. To date, there is no report on the molecular characterization of any Orf virus with other isolates around the world in mainland China. Further, the above results may provide some insight into the genotype of the etiological agent responsible for the contagious ecthyma dermatitis outbreak in the Jilin province, and could also provide a comparative view of the central coding region genomics of parapoxvirus (PPV).