Isolation Identification and Biological Characteristics of an Attenuated Strain of Pseudorabies Virus

A virus isolate designated F971 was isolated from pigs in Shanghai.The virus isolate was purified by plaque technique on CEF monolayer and the titer was 10 7.59 TCID 50 /ml.Virus Neutralization (VN)test showed that the isolate could be neutralized by PRV positive serum.Envelope and peplomers were observed on the surface of the virus under electron microscope.The virus isolate was pathogenic to 3 day mice and safe to rabbits and neonatal pigs.The neonatal pigs inoculated different doses(10 0 ,10 -1 ,10 -2 )of the isolate showed no clinical signs after challenged with a virulent strain of PRV 14 days postvaccination. Weaned pigs acquired high titer maternal antibodies from vaccinated sows and could be protected against PRV infection.Antibody to the isolate was detected from the vaccinated pigs with PRV antibody test kit(for screening),but not detected with PRV g I antibody test kit.According to the above results,it was suggested that the virus isolate was an attenuated PR virus with g I deletion.