Isolation and comprehensive characterization of bovine parvovirus 1 from diarrheic calves in Northeast China: Insights into evolution and biology.

Bovine parvovirus (BPV) is among the pathogens associated with respiratory, digestive, and reproductive disorders in cattle, contributing to significant economic losses in the global cattle industry. To investigate the prevalence and genetic variability of BPV in diarrheic cattle, 14 BPV strains were isolated from 673 bovine diarrhea samples (2017-2022, Northeast China) using BT cells. Notably, the DQ7498 strain exhibited the highest proliferation efficiency (titer reaching 10^8.12TCID₅₀/mL). Sensitive cell detection assays showed isolated strains stably serially passaged only in BT and bovine lung cells. Electron microscopy revealed that all isolates as non-enveloped icosahedrons structures (approximately 25 nm in diameter), consistent with parvovirus morphology. Complete coding sequence (CDS) and phylogenetic analysis revealed that the 14 isolates strains were closely related to BPV1 reference strains (DQ335247, NC001540), with high genetic identity (96.5%-99%). Recombination analysis identified genomic recombination events in four strains (JL108, JL60, DQ7706 and DQ7728), suggesting DQ8186 and ZD0510, or earlier unisolated strains, as potential parental strains. Amino acid sequence analysis revealed multiple coding mutations among the 14 isolates. Although antigenic epitope mutations (A362T and N399D) were identified in VP2, they did not induce significant conformational changes. Physicochemical characterization demonstrated that the virus exhibited sensitivity to chloroform and loses its infectivity after chloroform treatment, which is inconsistent with previous research reports. This study reports the first isolation of 14 BPV1 strains in Northeast China, revealing BPV1 genetic evolution, antigenic variation, and the first documented recombination events among regional strains, providing new insights into the molecular evolution of BPV1 and disease control.