Porcine circovirus type 3 (PCV3) is an emerging pathogen with high genetic variability, posing a continuous challenge to swine health and disease control. Ongoing viral evolution highlights the need for molecular surveillance to monitor circulating PCV3 strains. From 2023 to 2024, 257 blood and tissue samples from pigs with reproductive and respiratory disorders were collected in Henan Province, China. PCV3 was detected in 21.79% (56/257) of samples by quantitative real-time PCR (qPCR). Genetic characterization of 15 new PCV3 strains showed 98.95–99.95% nucleotide (nt) identity among themselves and 98.70-99.85% identity with global reference strains. Phylogenetic analysis of the ORF2 genes identified PCV3a-1, PCV3a-2, PCV3a-IM, PCV3b, and PCV3c subtypes, with PCV3b predominating. Notably, a genetically divergent strain, HN240609, clustered within the PCV3c subgroup. Additionally, multiple unique amino acid (aa) mutations were observed in the predicted T-cell and B-cell epitope regions of the capsid (Cap) protein (R10K, A35V, T102A, T102S, F104Y, T170A, and V180I). Genetically diverse PCV3 strains are co-circulating in Henan Province, and mutations in antigenic regions of the Cap protein may facilitate immune evasion. Continuous molecular surveillance is therefore essential for effective PCV3 prevention and control.
Song et al. (Mon,) studied this question.