Equine penile squamous cell carcinomas are associated with the presence of equine papillomavirus type 2 DNA sequences.
Authors: Knight C G, Munday J S, Peters J, Dunowska M
Journal: Veterinary pathology
Summary
# Editorial Summary This 2011 study investigated whether equine papillomavirus (EqPV) type 2 contributes to the development of penile squamous cell carcinomas (SCCs) in horses, a condition typically affecting older stallions and geldings with a mean age of 23.9 years. Using polymerase chain reaction screening on 40 penile samples from northeastern US horses—20 with SCC and 20 with other penile diseases—Knight and colleagues detected EqPV-2 DNA in 45% of SCC cases but only 5% of non-SCC penile conditions, representing a nine-fold higher prevalence in malignant tumours. Whilst confirmation by in situ hybridization and immunohistochemistry was less consistent, the strong association between EqPV-2 presence and SCC development mirrors established papillomavirus-cancer relationships in other species and humans, suggesting a potential aetiological role rather than mere incidental infection. For practitioners, this finding implies that stallions and geldings presenting with penile masses warrant thorough diagnostic evaluation and potentially closer monitoring, though further work is needed to establish whether EqPV-2 detection should inform prognosis or treatment strategy in clinical management.
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Practical Takeaways
- •Older stallions (average age 24 years) presenting with penile SCC should be considered at higher risk for equine papillomavirus type 2 infection; screening may inform prognosis and management
- •The strong association between EPV-2 and penile SCC suggests potential causative role; monitoring breeding soundness and considering breeding restrictions may be warranted in affected animals
- •Early detection and removal of penile lesions becomes increasingly important given the papillomavirus association and advanced age of affected horses at diagnosis
Key Findings
- •Equine papillomavirus type 2 DNA was detected in 45% (9/20) of horses with penile squamous cell carcinoma versus only 5% (1/20) of horses with non-SCC penile disease
- •Mean age of horses with SCC was 23.9 years compared to 13.3 years for non-SCC penile disease cases
- •This is the first report of equine papillomavirus type 2 infection documented in North American horses
- •In situ hybridization confirmed papillomavirus presence in 6 of 10 PCR-positive cases, though immunohistochemistry was positive in only 1 case