Identification of bovine papillomavirus types by PCR on biopsies of equine sarcoid in Chile

Neoplasms are an important cause of morbidity and mortality in horses, with approximately 50% of cases related to the integumentary system. Equine sarcoid is the most common cutaneous neoplasm of this species worldwide and it is characterized by its locally aggressive behavior. Cross-species infection by the Bovine Papillomavirus (BPV) genus Deltapapillomavirus (types BPV-1, BPV-2, and BPV-13) is a key factor for sarcoid development. However, no studies have been conducted in Chile on the prevalence and distribution of the disease or the identification of circulating BPV types. Therefore, this study focused on identifying the BPV types present in equine skin biopsies from different regions of the country. For this study, 23 paraffin blocks of equine biopsies with a histopathological diagnosis of sarcoid were collected from five localities in Chile, including cases from 2004 to 2025. Histopathological diagnoses were verified before DNA extraction, and PCRs were performed to detect BPV-1, BPV-2, and BPV-13. Fisher’s exact test was applied to evaluate the associations between viral type and sex, breed, and age of the sampled individuals. Of the 23 samples analyzed, 100% met at least one histopathological criterion for inclusion in the study. PCR analysis revealed that 35% (8/23) of the samples tested positive for BPV-1, 91% (21/23) tested positive for BPV-2, 26% (6/23) exhibited co-detection of BPV-1 and BPV-2, and no sample (0/23) tested positive for BPV-13. Regarding geographical distribution, BPV-1 was identified in three regions, whereas BPV-2 was identified in all five regions (5/5). There were no statistically significant associations between viral type and sex, breed, or age (P > 0.05). This study provides a baseline for the viral characterization of this equine disease across the country, allowing for the development of prevention and treatment strategies that align with the context of the affected local population.