Reproductive tract herpes-like lesions associated with bovine herpesvirus 4 in dairy cows

Reproductive tract herpes-like lesions have been sporadically observed in dairy cows, but their pathological definition and etiological relevance remain unclear. In China, bovine herpesvirus 4 (BoHV-4) has recently gained attention as a pathogen associated with reproductive disorders in dairy cattle, including vulvovaginal herpes-like lesions and reproductive tract hemorrhage. In this case series, dairy cows presenting with a distinct clinical phenotype characterized by reproductive tract herpes-like lesions were investigated across different physiological stages. While herpes-like lesions were observed in all examined groups, hemorrhagic erosions of the reproductive tract mucosa were predominantly identified in early postpartum and dry cows. Pathological, molecular, and virological analyses were performed on lesion-associated tissues. BoHV-4 DNA was predominantly detected in samples from pregnant, dry, and early postpartum cows, whereas tissues from neonatal calves and replacement heifers were consistently negative. Infectious BoHV-4 was successfully isolated from lesion tissues and characterized by immunofluorescence assay and transmission electron microscopy. Histopathological analysis revealed multi-focal epithelial degeneration accompanied by cytoplasmic vacuolation, scattered focal epithelial necrosis, and diffuse inflammatory infiltration within the lamina propria, and immunohistochemistry demonstrated BoHV-4 antigen localization in lesion-associated epithelial and subepithelial regions. Although definitive causality cannot be established, the combined molecular, virological, and pathological findings support an association between BoHV-4 infection and this reproductive tract herpes-like clinical phenotype, which may represent a previously underdefined clinical-pathological presentation in dairy cows, particularly during specific physiological stages.