Equus caballus papillomavirus Type 7 is a rare cause of equine penile squamous cell carcinomas.
Authors: Munday John S, Knight Cameron G, Bodaan Christa J, Codaccioni Camille, Hardcastle Michael R
Journal: Veterinary journal (London, England : 1997)
Summary
# Editorial Summary: EcPV7 and Equine Penile Squamous Cell Carcinomas Whilst Equus caballus papillomavirus type 2 (EcPV2) is well-established as the primary aetiological agent of equine penile squamous cell carcinomas, a substantial proportion of cases yield negative results on EcPV2 testing, prompting investigation into alternative papillomavirus types. Munday and colleagues employed PCR-based molecular analysis on archived penile and oropharyngeal tumour samples to determine the prevalence and distribution of EcPV7, a previously unreported equine pathogen, alongside EcPV2. Of 20 penile SCC samples tested, EcPV7 was detected as a mono-infection in 5% of cases, as a co-infection with EcPV2 in 25%, and EcPV2 alone in 70%; notably, EcPV7 was also identified in 30% of oropharyngeal SCCs, exclusively as a co-infection with EcPV2. The clinical and histopathological presentation of EcPV7-associated lesions proved indistinguishable from EcPV2-driven carcinomas, meaning routine examination cannot differentiate between the two aetiologies. These findings carry significant implications for prevention strategies: current or future EcPV2-specific vaccines may not provide complete protection against penile squamous cell carcinomas, as a minority of cases are driven by other papillomavirus types, and practitioners should remain cognisant that negative EcPV2 results do not exclude papillomavirus involvement in tumour development.
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Practical Takeaways
- •Veterinarians should be aware that equine penile SCCs may be caused by EcPV7 in addition to EcPV2, which may affect diagnostic and vaccine strategies
- •Current EcPV2-targeting vaccines may not provide complete protection against all papillomavirus-associated penile carcinomas; broader-spectrum vaccines may be needed
- •Clinical and histological features cannot differentiate between lesions caused by EcPV7 versus EcPV2, so molecular testing may be required for accurate characterization
Key Findings
- •EcPV7 was detected as the sole papillomavirus in 1 of 20 penile SCC cases and as a co-infection with EcPV2 in 5 of 20 cases
- •EcPV7 DNA was identified in 3 of 10 oropharyngeal SCC samples, all as co-infections with EcPV2
- •EcPV7 is capable of causing equine penile squamous cell carcinomas, representing the first evidence that papillomavirus types other than EcPV2 can cause these neoplasms
- •Current EcPV2-only vaccines may not prevent all equine penile squamous cell carcinomas given the disease-causing potential of EcPV7