Epidemiological and evolutionary analysis of porcine circovirus type 2 within pig populations in central China during...

Porcine circovirus type 2 (PCV2) is a major swine pathogen associated with immunosuppression and diverse clinical syndromes, posing a persistent threat to the pig industry. Updated epidemiological and molecular data are essential for effective disease control. In this study, a total of 14,436 samples collected from 18 cities in Henan Province, central China, between 2021 and 2024 were examined for PCV2 using real-time PCR. Prevalence was analyzed according to year, season, region, and farm source, and farm-level infection rates were also assessed. In addition, 30 PCV2 whole genomes were sequenced and genetically characterized. Overall, PCV2 was detected in 22.32% (3,222/14,436) of samples and was present in all surveyed cities, with prevalence ranging from 6.47% to 49.93%. Temporal analysis revealed a peak in 2022 and a consistently lower prevalence in the third quarter. Significant geographic heterogeneity was observed across regions. PCV2 prevalence was highest in samples from diseased pigs, followed by slaughterhouses, whereas commercial and breeding farms showed lower detection rates. Multivariable logistic regression confirmed that region, season, and farm type were independently associated with PCV2 positivity. Phylogenetic analysis based on ORF2 sequences showed that PCV2d was the predominant genotype, alongside PCV2a and PCV2b, and sequence comparison revealed notable divergence from commonly used vaccine strains. These findings demonstrate that PCV2 remains widely circulating in central China, with distinct epidemiological patterns and ongoing genetic evolution, underscoring the need for continuous surveillance and optimized vaccination strategies.