Abstract
Pseudorabies (PR), caused by variant pseudorabies virus (PRV), is an economically important viral disease in China. Recently, PRV infection in humans has also received attention worldwide. To investigate the PRV infection in Hunan province, China, we collected a total of 18,138 serum specimens from 808 PRV-vaccinated pig farms cross this region during 2016–2020, and we detected the presence of PRV glycoprotein B (gB) and gE-specific antibodies. The enzyme-linked immunosorbent assay (ELISA) results revealed that 80.47% (14,596/18,138, 95 CI 79.9–81.0) and 23.55% (4,271/18,138, 95 CI 22.9–24.2) of serum samples were positive for PRV gB and gE-specific antibodies, respectively. Further analysis indicated that the seroprevalence of wild PRV infection was associated with the season and breeding scale (p < 0.01). In addition, five PRV strains were isolated from PRV-positive samples in Vero cells and the virus titers varied from 106.5 to 107.51 TCID50/0.1 ml. The phylogenetic analysis revealed that one isolate was a classical strain of PRV genotype II, and four other isolates belonged to the variants of genotype II. Collectively, the data indicate that the prevalence of PRV remains high in pigs in Hunan province, and the variant PRV strains are the major genotypes affecting the development of the pig industry.
Highlights
Pseudorabies virus (PRV) is a double-stranded linear DNA virus with ∼143 kb and encoding more than 70 proteins belonging to the genus Varicellovirus of the subfamily Alphaherpesviridae [1]
Anti-glycoprotein E (gE) antibody levels in serum were determined by using commercial blocking enzyme-linked immunosorbent assay (ELISA) Kits (Cat: CP144, IDEXX Laboratories, Westbrook, ME) according to the manufacturer’s instructions, which can differentiate the vaccine strain from the wild pseudorabies virus (PRV) strains
Data obtained from the ELISA assay demonstrated that 68.56% (554/808, 95% confidence intervals (CIs) 65.4–71.8) of the investigated pig farms meet the national requirement, in which the PRV-glycoprotein B (gB) sero-positive rate of the pig population should be higher than 70% after immunization, while the proportion of PRV-gE-positive farms was up to 43.19% (349/808, 95% CI 39.8–46.6), indicating that the current vaccines could not provide complete protection
Summary
Pseudorabies virus (PRV) is a double-stranded linear DNA virus with ∼143 kb and encoding more than 70 proteins belonging to the genus Varicellovirus of the subfamily Alphaherpesviridae (family Herpesviridae) [1]. Pseudorabies (PR) or Aujeszky’s disease caused by PRV is a major threat to the pig industry in China, and the symptoms of PR are mainly characterized by reproductive failure in sows, fatal encephalitis and neurological symptoms in newborn piglets, and respiratory disorders in fattening pigs [2, 3]. Pig is the natural host and reservoir for PRV, while this pathogen can infect various mammals, such as ruminants [4, 5], carnivores [6], bears [7], etc. A PRV strain has been isolated from an acute human encephalitis case, suggesting that humans may be potential PRV hosts [8]. PRV-triggering diseases have frequently been documented in Bartha-K61-immunized swine populations in China since late 2011 [10, 11]. Molecular analysis revealed that the causative agents were identified as PRV variants, which have high genetic variations in some antigenic regions (as gC, gD, and gE) compared to the classic PRV strains [12, 13]
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