Investigation on pseudorabies prevalence in Chinese swine breeding farms in 2013-2016.

Pseudorabies (PR) has been prevalent in Chinese swine breeding farms since the outbreak at the end of 2011. For investigating current prevalence of PR, a nationwide surveillance has been performed in this study. The swine serum samples were collected from 93, 100, 92, and 91 swine farms in China during 2013-2016, respectively. Since the extensive use of gE-deleted pseudorabies virus (PRV) vaccine, we could apply the PRV-gE antibody for determining wild-type virus infection and the PRV-gB antibody for evaluating vaccine immunization. The results were concluded as follows: (1) Nationally, the positive rate of PRV-gB was maintained at a high level (> 90%), while the positive rate of PRV-gE continued to decrease (from 22.17 to 13.14%). (2) The positive rates of PRV-gE were greatly varied in different geographical regions and swine farms (0~100%), while the positive rate of PRV-gB was generally high (> 90%). (3) The number of imported PRV attenuated vaccines were about twice that of domestic PRV attenuated vaccines, while the positive rate of PRV-gB was not significantly different (P > 0.05). (4) The performance of PR eradication developing or developed farms was better than the performance of common farms, with higher positive rate of PRV-gB (> 90%) and much lower positive rate of PRV-gE (nearly 0%).