Molecular epidemiology and evolution of porcine parvovirus 1

Porcine parvovirus 1 (PPV1) is a pathogenic agent of infectious reproductive diseases. However, systematic studies on the molecular evolution of PPV1 are still relatively limited worldwide. Our research findings indicate that PPV1 can be classified into four evolutionary groups (Groups I–IV), with Group IV being the dominant group. Over time, the variation within the genotype has shown a declining trend. The nucleotide substitution rate of PPV1 is approximately 8.36 × 10⁻⁵ per site per year, suggesting that its most recent common ancestor appeared around 1891. Since 2005, the effective population size of PPV1 has shown a decreasing trend. In selection pressure analysis, only a few positive selection sites were identified, with Group III having more positive selection sites compared to other evolutionary groups. These results suggest that PPV1 may be gradually evolving towards a more conserved state. Additionally, 1,644 tissue samples were tested via polymerase chain reaction (PCR), with a positivity rate of 4.93% (81/1,644）between 2022 and 2024. Subsequently, 14 PPV1 strains were isolated and identified, and a phylogenetic tree was constructed, revealing that no strains were located in Group I; five strains were in Group II; three strains in Group III; and six strains in Group IV. Furthermore, amino acid differences between the evolutionary groups were also observed. In conclusion, this study provides a systematic description of the genetic characteristics and molecular evolution of PPV1.