Combining RNAScope and RCA reveals a novel epitheliotropic bovine xipapillomavirus in udder papillomas

The diversity of papillomaviruses (PVs) remains largely unexplored, with many viral types still unidentified among mammalian hosts. Data on PV presence is particularly scarce in several regions of the world, including Central America. In this study, we report the identification and characterization of a novel Xipapillomavirus detected in udder papillomas from two dairy cows in Costa Rica. A combination of histopathology, RNA in situ hybridization (RNAScope), rolling circle amplification (RCA), and sequencing confirmed the viral presence, enabling genetic characterization and assessment of its cellular tropism. Based on our findings, we propose classifying this novel PV as a new type within the Bovine papillomavirus species, designated BPV45. Results revealed that BPV45 is an epitheliotropic virus closely related to BPV12 and belongs to the species Xipapillomavirus 1. Further research is needed to confirm the viral tropism for bovine udder tissue and to evaluate the potential economic impact on milk production and lactation performance.