Dose-dependent pathogenicity of a pseudorabies virus variant in pigs inoculated via intranasal route

Pseudorabies (PR) or Aujeszky's disease (AD), caused by pseudorabies virus (PRV), is an economically important viral disease in many countries. The modified live vaccine Bartha-K61 strain has played an important role in the control of PR in many countries including China. Since late 2011, however, increasing PR outbreaks caused by an emerging PRV variant have been reported in Bartha-K61-vaccinated swine population on many farms in China. Previously, we showed that the PRV variant TJ strain exhibited enhanced pathogenicity in pigs inoculated via intramuscular route. To develop an animal infection model for accurate evaluation of novel vaccines against the emergent PRV variant, we evaluated the pathogenicity of the PRV TJ strain of different doses in pigs infected via intranasal route. Groups (n=5) of 7-week-old healthy pigs were inoculated intranasally with 10(3), 10(4), 10(5), or 10(6) TCID50 (median tissue culture infective dose) PRV TJ strain. Clinical signs, rectal temperature, virus shedding, pathological changes, and seroconversion were monitored. The results showed that the PRV TJ strain induced varied morbidity and mortality (0/5 to 5/5), clinical signs, and tissue lesions, increasingly correlated with the infection doses, and the median lethal dose (LD50) of the virus was determined to be 10(4.5) TCID50. Together, this study demonstrates the dose-dependent pathogenicity of the PRV variant via the intranasal route of infection, which provides an ideal animal infection model for evaluation of novel vaccines against the emerging PRV variant.