Epidemiological investigation and gC, gE, TK genetic characteristics of pseudorabies virus in Sichuan province of China between 2018−2019

Abstract:

[Background] Pseudorabies virus (PRV) is an important pathogen to pig industry, a large-scale of pseudorabies (PR) has swept many Bartha-K61-vaccined farms in China since 2011. [Objective] In order to investigate the epidemiological characteristics of PRV strains prevalent in Sichuan province, China, 384 suspected PRV infected samples were collected from 86 pig farms in 2018?2019. [Methods] According to the amplification of PRV-gE gene, 384 samples were detected by PCR. The positive rates of PRV in different seasons and regions were counted, and the correlation between PRV infections and clinical symptoms was statistically analyzed. We selected some PRV positive samples for virus isolation through BHK-21 cells, followed by gC, gE and TK genetic informatic analysis of isolated strains. [Results] The individual positive rate of PRV was 9.9% (38/384); the group positive rate of PRV was 16.3% (14/86); the positive rate in aborted fetuses was 32.1% (27/84); the positive rate in semen of breeding boars was 2.0% (4/198); the positive rate in nervous symptoms pig was 11.4% (4/35); the positive rate in respiratory symptoms pig was 4.5% (3/67). Statistical analysis indicated that PRV infection was associated with pig reproductive failure (P<0.01). The highest PRV infection rate was detected in winter (December, January, February), with a positive rate of 33.0% (31/94); Spring (April, March, May) ranked the second highest positive rate of 9.1% (3/33); Summer and autumn was about 1.5% (2/130) and 1.6% (2/127) respectively. Totally, we isolated 3 PRV strains between 2018?2019, named PRV-SN, PRV-DJY, PRV-CD respectively. PRV-XJ, a strain isolated by our laboratory in 2016 in Sichuan province was also included, these strains were used for gC, gE, TK gene sequencing. Sequence alignment shows that Sichuan isolates were similar to those Chinese isolates, except for sporadic mutations and deletions. [Conclusion] Farms should strengthen the purification of pseudorabies in breeding herds.