Isolation And Identification Of ORF Virus And Its Gene Sequence Analysis In Shaanxi Guanzhong

Contagious ecthyma, commonly known as sore mouth, also known as scabby mouth orcontagious pustular dermatitis caused by Orf virus, which belongs to the genus Parapoxvirus,subfamily Chordopoxvirinae, family Poxviridae. Orf is an acute and epitheliotropic zoonoticskin disease that can make sheep, goats and some domesticated or wild ruminants infected. Thelambs are the most susceptible to this disease, the morbidity may reach up to100%and mortalitydue to secondary bacterial infections may get to15%. What’s more, humans particularlyveterinarians, farmers and meat porters have very high rate to contact with infected animals orfood. So once Orf outbreak, it not only causes huge economic losses to farmers and causesserious damage to the development of sheep and goats industry, but also poses a threat to foodsafety and public health. In recent years, lots of China’s provinces have reported Orf outbreak.Given the endemic nature of Orf and the fact that northwest China is the traditional animalhusbandry base, the outbreak rate of Orf is usually high. In March of2013, one suspected acuteoutbreak of contagious ecthyma occurred in a farm, in Guanzhong region of Shaanxi province ofChina. In this research, we will make a statistics on the infected goats in this farm and isolate anew ORFV, then identify the new strain and analyze the important gene sequences. All of theresults of this study would provide theoretical basis for thoroughly investigate the etiology andepidemic situation of this disease in Shaanxi province and study the pathogenic mechanism. Theresults are as follows.1. On the clinical observation of infected goats, they showed typified lesions that beganwith small red spots, papules and pustules, before forming thick nigger-brown scabs on the skinof the lips and tongue, around the nostrils and on the oral mucosa. In this farm, the morbidity ofOrf was21.3%and the mortality of Orf was5%. On the histopathological examination of liplesions, the spinous cells of the stratum spinosum showed acanthosis and ballooningdegeneration. Using the PCR technology to detect the B2L, F1L and VIR genes of111scabs,expected fragments were amplified, which manifested the infected goats were infected by ORFVin this farm. Sequencing the23B2L, F1L and VIR genes of positive samples selected at random,the results were same, which suggested that we could chose a positive sample for virus isolation at random.2. Using MDBK cells to isolate ORFV from positive scabs, the cells showed cytopathiceffect on the fifth generation after virus inoculating into MDBK cells. The electron microscopicexamination showed typical virions which were ovoid and had a spiral crisscross on the surface.From physico-chemical property test, the isolate was DNA virus and its virulence was stable andsensitive to ethyl ether, chloroform and so on. Finally, expected fragments were amplified fromthe new isolate by using PCR. So a new Orf virus, named as ORFV-SXGZ was successfullyisolated.3. The B2L, F1L and VIR genes of ORFV-SXGZ were cloned, compared the homology ofnucleotide and amino acids sequence with other PPVs. The results showed that the homology ofB2L, F1L and VIR genes were84.2%～99.6%,74.5%～97.9%and67.0%～99.3%, respectively.The homology of deduced amino acids sequence between ORFV-SXGZ and other strains were83.6%～99.7%,65.7%～98.5%and52.2%～98.4%, respectively. The phylogenetic treesshowed that the ORFV-SXGZ strain was not only closer to the strains isolated from diseasedsheep herds, but also was closer to the strains isolated from diseased goat herds. The three geneswere all closer to the northwest strains. Alignment of deduced amino acid sequences of thisisolate showed that part of the genes were different from other reported epidemic ORFV Chinesestrains, part of the genes were as the same as some northwest strains.In conclusion, ORFV infection exsited in Shaanxi Guanzhong and we successfully isolatedone Orf virus and analyzed sequences of part genes. The results would provide theoretical basisfor study the epidemic regular, the pathogenic mechanism and immunological control.