Epidemiological characteristics and structural-functional implications of spike protein variations in a bovine coronavirus isolate from diarrheic calves

Bovine coronavirus (BCoV) is an important pathogen associated with enteric disease in calves, contributing to significant economic losses worldwide. To provide an updated overview of BCoV epidemiology, we conducted a systematic review and meta-analysis of studies published up to October 2025. Seventy-two eligible studies comprising 29,045 samples from nine countries were included, yielding a pooled global prevalence of 20.39% (95% CI: 15.07-26.99). Substantial heterogeneity was observed, reflecting variations in geographic regions, detection methods, and study populations. To complement the epidemiological analysis, 298 fecal samples from diarrheic calves in northeastern China were screened by RT-PCR, identifying 36 BCoV-positive samples (12.08%). Co-infection analysis revealed that most positive samples contained additional enteric viruses, indicating complex viral interactions in calf diarrhea. A novel BCoV strain was isolated in MDBK cells and designated DDFX98. Viral identity was confirmed by PCR, transmission electron microscopy, and immunofluorescence assay. Complete genome sequencing demonstrated that DDFX98 belongs to the GIIb subtype and shares high nucleotide identity with contemporary circulating strains. Comparative analysis of the spike (S) protein revealed multiple amino acid substitutions predominantly located within the S1 subunit. Structural modeling suggested localized conformational variations, particularly in surface-exposed and flexible regions, while preserving the overall spike architecture. In silico predictions further indicated minor alterations in glycosylation potential and epitope-associated regions. Collectively, this study integrates global epidemiological evidence with molecular and structural characterization of a contemporary BCoV isolate, providing insights into S protein variability and its potential structural - functional implications.