Isolation and phylogenetic analysis of orf virus from the sheep herd outbreak in northeast China

From the recent outbreak of a sheep herd in Nongan, northeast of China, the novel orf virus (ORFV) strain NA1/11 was successfully isolated. Western blot analysis indicated that the NA1/11 strain cross reacts with monoclonal antibody A3 and infected sheep ORFV antiserum. The purified virions revealed the typical ovoid shape when observed by atomic force microscopy. To determine the genetic characteristics of the NA1/11 strain, the sequences of ORFV011 (B2L), ORFV059 (F1L), ORFV109, ORFV110 and ORFv132 (VEGF) genes were amplified and compared with reference parapoxvirus strains. Non-metric multidimensional scaling (nMDS) was performed to analyze the nucleotide similarities between different ORFV strains.Phylogenetic analysis based on ORFV 011 nucleotide sequences showed that the NA1/11strain was closely related to Xinjiang and Gansu strains. ORFV110 and ORFV132 genes are highly variable. The results revealed that precise phylogenetic analysis might provide evidence for genetic variation and movement of circulating ORFV strains in Northeast China. In addition, nMDS analysis showed that geographic isolation and animal host are likely major factors resulting in genetic differences between ORFV strains.Orf, also known as contagious pustular dermatitis or contagious ecthyma, is an epitheliotrophic disease that mainly affects sheep, goats, wild ruminants, and humans with a worldwide distribution [1-3]. The lesions are characterized by maculopapular, vesicular pustules that mainly affect the skin around the lips, mouth muzzle, nostrils, teats, and oral mucosa and rarely extend into the esophagus, stomach, intestine, or the respiratory tract of sheep, goats and wild animals [3-6]. In humans, the most common lesions are self-limiting, painful pustules on the hands and fingers [3,4]. The infective lesions are usually confined to the areas surrounding the virus entry sites. The development stages include erythema, vesicles, pustules, and scabs [6,7]. Primary lesions are usually