Complete genomic characterization of bovine papillomavirus type 1 and 2 strains infers ongoing cross-species transmission between cattle and horses.
Authors: Gysens L, Vanmechelen B, Maes P, Martens A, Haspeslagh M
Journal: Veterinary journal (London, England : 1997)
Summary
# Editorial Summary: BPV Cross-Species Transmission and Equine Sarcoid Development Equine sarcoids, the most prevalent skin tumours in horses, are caused by bovine papillomavirus types 1 and 2 (BPV-1/-2), yet these same viruses typically regress in cattle—a clinical paradox that has prompted investigation into whether horse-specific viral variants might explain this difference. Gysens and colleagues sequenced 98 complete BPV-1/-2 genomes from equine and bovine sources using Nanopore technology, then constructed phylogenetic trees and tested for host-specific genetic clustering using Bayesian analysis. Despite identifying 179 unique BPV-1 and 128 BPV-2 substitutions overall (including notable deletions of up to 1.5 kb in the L1/L2 region found only in horse samples and 81% non-synonymous mutation rates in the E2 region), the most frequently detected variants were shared between species, with no statistically significant phylogenetic-host correlation. These findings suggest that BPV transmission from cattle to horses remains an active, ongoing process rather than an ancient event followed by viral adaptation—challenging the hypothesis that horse-specific variants drive persistent sarcoid development. For equine practitioners, this underscores the importance of biosecurity measures to limit cattle-horse contact and continued investigation into host factors (immune response, wound characteristics, anatomical predisposition) rather than viral genetics alone as drivers of sarcoid persistence in equine populations.
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Practical Takeaways
- •Equine sarcoids may result from repeated cross-species transmission of BPV from cattle rather than horse-specific viral variants, suggesting epidemiological control should focus on cattle-horse contact management
- •The absence of horse-adapted BPV variants explains why equine sarcoids persist and recur unlike regressive BPV papillomas in cattle—horses lack biological adaptation to the virus
- •Veterinarians managing horses with sarcoids should consider herd epidemiology and potential cattle exposure when developing treatment and prevention strategies
Key Findings
- •179 unique BPV-1 and 128 unique BPV-2 substitutions were identified across 98 complete genomes using Nanopore sequencing
- •E2 coding region showed exceptionally high non-synonymous mutation rate of 81% (13/16 mutations)
- •Large deletions in L1/L2 region (up to 1.5 kb) were found exclusively in horse-derived samples
- •Most frequent SNPs were shared between equine and bovine hosts with no phylogeny-host correlation, indicating ongoing cross-species transmission from cattle to horses rather than ancient horse-adapted variants