Prevalence and Genetic Variation Investigation of the Pseudorabies Virus in Southwest China

In 2022, a significant PRV outbreak in a southwestern China pig farm led to a high incidence of sow abortion. A serological analysis using <i>gE</i> antigen-based ELISA revealed a high prevalence (69.30%) of PRV <i>gE</i> antibodies among the affected pigs, with a significant variation across different pig populations (1.11-76.12%). We collected additional 5552 pig serum samples and 580 pig cerebrospinal fluid (CSF) samples from various pig farms in Southwest China between 2022 and 2024. The seropositive rates for PRV <i>gE</i> antibodies ranged from 2.36% and 8.65% in the serum samples, while the positive detection rates for the PRV <i>gE</i> gene in the cerebrospinal fluid samples, as determined by PCR, were between 1.06% and 2.36%. The PCR analysis and sequencing of the PRV <i>gB</i>, <i>gC</i>, <i>gE</i>, and <i>TK</i> genes from eight randomly selected samples identified two distinct strains, CQ1 and CQ2. CQ1's <i>gC</i> gene showed similarity to the vaccine strain Bartha, while the other genes aligned with Chinese classical strains, suggesting its potential genetic recombination. CQ2 aligned with the Chinese classical strain SC. Although the overall PRV infection in Southwest China's pig farms is relatively low, occasional outbreaks with high positivity rates are observed. These findings highlight the necessity for increased surveillance and stringent control measures to safeguard the swine industry.