| Contagious ecthyma, also known as orf, is a zoonosis which primarily affects sheep and goats. The main clinical symptoms of the disease are papules, vesicles, pustules and crusting warty at the lips, oral mucosa, nose, breast mucous membranes and some other surrounding skins, In endemic areas, morbidity and mortality of orf were 90% and 10% respectively, which had caused numerous economic losses.Yulin and Weinan Cities are major cashmere and dairy goats breeding areas respectively in Shaanxi Province and had become characteristic industries in Shaanxi Province. In recent years, orf had occurred repeatedly in the two regions, but the epidemic status of the two areas are not very clear, which directly affects the development of the prevention and control strategies.In this study, molecular etiology investigation of orf were taken in Yuyang, Hengshan, and Shenmu counties of Yulin city and Fuping county of Weinan city, and inactivated vaccine were prepared using a previous isolated ORFV strain(FX0910 strain) and assayed the safety and immune effect. The main contents and results of this study are as follows:1.Molecular etiology investigation of orfBlood samples were collected in Yuyang, Hengshan, Shenmu and Fuping respectively, and the viral genomic DNA were extracted by the NaI method and detected by the method of PCR which had been established previously in our laboratory. The results suggested that the detection rate of orfV(orf virus) varied in different areas, which were 30%, 29.6%, 24.1% and 82.6% in Yuyang, Hengshan, Shenmu and Fuping respectively.2.Preparation and immune effect assay of inactivated vaccineThe orfV FX0910 strain isolated in our laboratory were amplified on calf testis primary cells and the titer was assayed by the method of Reed-Muench. The virus was treated by methanol in a concentration of 0.4% for 48 h. And then the virus was inoculated on calf testis primary cells and lips of lambs to test whether it had been inactivated completely. The inactivated virus was mixed with aluminum hydroxide adjuvant to be prepared as inactivated vaccine and inoculated on groin of lambs to test the safety.120 pregnant ewes were immunized with the inactivated vaccine on neck subcutaneously 2 mL per goat, and 80 pregnant ewes were treated with medium as control. All the pregnant ewes used in the experiment were predicted to be parturition 35-45 days later. Peripheral blood samples were collected to detect orfV by PCR and neutralizing antibodies by neutralization test before immunization and 14 d after first and second immunizations. Cord blood samples of the newborn lambs were collected to detect orfV by PCR and calculate the morbidity.The results were as follows: the titer of the orfV proliferated on calf testis primary cells was 106.8TCID50/100 μL. The virus treated with methanol was inactivated completely as it could not result in obvious CPE on calf testis primary cells or symptoms on lambs. The detection rates of orfV were 100% before immunization and 56.0% after twice immunizations, while the detection rates were 90.0% and 87.5% respectively in the control test. T in pregnant ewes of immunized or control group, while it raised up to 1:24.02 after twice immunizations with the inactivated vaccine. The detection rates of orfV in cord blood samples were 14.3% and 71.4% in immunized or control group respectively. The morbidities of the new born lambs were 0% and 36.7% in immunized or control group respectively. Conclusion: The orfV carrying status of the goats in the investigated areas were clear. The effects of the inactivated vaccine were raising the neutralizing antibodies and reducing orfV in pregnant ewes, reducing orfV in the newborn lambs and improving their anti-viral abilities.Effectively prevent orfV infected the fetal sheeps through placenta. |
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