Bovine and ovine deltapapillomavirus coinfection associated with equine sarcoid

Papillomaviruses (PV) are significant agents capable of inducing simple, multiple, and/or proliferative lesions in the dermis and epidermis of animals, known as cutaneous papillomatosis. These lesions can be benign or malignant and have been identified in various hosts, including mammals, birds, reptiles, and fish. PVs are strictly species- and tissue-specific, although some established and unusual cases of cross-infection, such as BPV in equine sarcoids, have been reported. Sarcoids are horses' most common skin tumors, which can be locally aggressive and cause significant clinical signs. It is recurrently associated with Bos taurus papillomavirus (BPV) and, more recently, Ovis aries papillomavirus (OaPV). Interestingly, OaPV2s, initially identified in sheep, have been detected in other species, such as horses, cattle, and pigs. Therefore, the present study aimed to detect and sequence PVs in an equine sarcoid through rolling circle amplification followed by high-throughput sequencing (RCA-HTS) on the Illumina MiSeq platform. Sequencing yielded 387,923 reads and 17 contigs classified as Deltapapillomavirus genus. A complete BPV1 genome, with 99% coverage, was sequenced, and partial E1 and L1 genes of OaPV2 were detected. Histopathological analysis revealed fibroblastic sarcoid, which has been associated with BPV1 and OaPVs. Our results agree with recent BPV and OaPV2 association observations in sarcoid lesions in equine and swine. This broad host range of OaPVs deserves attention, as it may indicate potential interspecies transmission that is not yet fully understood, especially in coinfections, which could influence viral dynamics, transmission patterns, and disease outcomes. Until now, only OaPV1, 3, and 4 had been detected in equine sarcoids; thus, this is the first detection of OaPV2 in an equine sarcoid. In conclusion, OaPV2 should be considered a potential etiological agent of sarcoids, particularly in association with BPV1.