Identification of Pseudorabies Virus Variant and Control of Pseudorabies

Due to variant strain,pseudorabies virus (PRV) has broken out again and spread in China since 2011.A swine farm in Guangdong province was found pseudorabies (PR) symptoms-like miscarriage after introduction.The study was carried out to identify and control the PR.Serum of sows with and without miscarriage were randomly collected and the PRV gB and gE were detected by ELISA method,and brain tissues of sick piglets were sampled and the PRV gH gene was tested by PCR.All the sows in the farm were emergently inoculated PRV variant strainin activated vaccine.Serum before and after immunization were collected and detected by ELISA and micro-serum neutralization test.ELISA results showed that gE antibody of all the breeding sows with miscarriage were positive,and that of sows without miscarriage showed weekly positive;The average gB ELISA S/P value of sows with miscarriage was as high as 4.0,while that of sows without miscarriage was over 3.0.PCR of 3 sick piglets were all positive and the sequence of gB gene was 100% identical to BJ-YT-2012,a wide variant stain in 2012. The result of detection of the sows serum at before and after immunization showed that the S/P value of gB rose up from 1.603 before immunization to 2.88 at four weeks after immunization,and the neutralizing antibody rose up from 1:24 to 1:213.This agreed with the results that the sows showed less probability of miscarriage since the first week after immunization and almost no miscarriage after two weeks after immunization.This study suggested that classical PRV vaccine was not effective in this case,while the vaccine made from the variant PRV strain was.