Equus caballus papillomavirus 8 (EcPV8) associated with multiple viral plaques, viral papillomas, and squamous cell carcinoma in a horse.
Authors: Peters-Kennedy J, Lange C E, Rine S L, Hackett R P
Journal: Equine veterinary journal
Summary
# Editorial Summary: EcPV8-Associated Papillomatosis and Malignant Transformation in Equine Dermatology Equus caballus papillomavirus 8 (EcPV8) represents an emerging pathogen in equine medicine with potentially serious clinical consequences; this 2019 case report documents the first confirmed association between EcPV8 infection and malignant squamous cell carcinoma progression. A 16-year-old horse presented with dozens of crusted papular and nodular lesions over four years, with recurring masses despite four surgical excisions and three courses of cisplatin chemotherapy to the inguinal region, ultimately diagnosed as multiple viral plaques, papillomas, squamous cell carcinoma in situ, and invasive squamous cell carcinoma via histopathology with EcPV8 DNA confirmed by PCR. This case is particularly significant as the first documented example of EcPV8-associated malignant transformation, joining only three previously reported cases of EcPV8-related viral papillomatosis, highlighting that our understanding of this virus's pathogenic potential and prevalence in the equine population remains incomplete. The recurrent nature of lesions despite aggressive intervention—including surgical removal and chemotherapy—suggests EcPV8 may establish persistent, potentially multifocal infections warranting reassessment of treatment protocols and surveillance strategies. Until epidemiological data clarify the true incidence of EcPV8 and its malignant transformation rates, practitioners should maintain high diagnostic suspicion for this virus in cases of recurrent papillomatous lesions, particularly in older horses, and consider PCR confirmation to guide management decisions and prognosis counselling.
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Practical Takeaways
- •EcPV8 should be considered as a differential diagnosis in horses presenting with recurrent or progressive crusted papular/nodular lesions, particularly in the inguinal region
- •Squamous cell carcinoma may develop secondary to EcPV8 infection; early identification and aggressive treatment may be warranted to prevent malignant transformation
- •Conventional surgical and chemotherapy approaches (excision and cisplatin) may be insufficient for EcPV8-associated lesions, suggesting need for alternative or adjunctive treatment strategies
Key Findings
- •A 16-year-old horse developed dozens of crusted papular to nodular lesions over 4 years in the inguinal region associated with EcPV8
- •Histopathology confirmed multiple viral plaques, viral papillomas, SCC in situ, and invasive squamous cell carcinoma, all associated with EcPV8 DNA detected via PCR
- •This is the first reported case demonstrating an association between EcPV8 and squamous cell carcinoma in a horse
- •Surgical excision and cisplatin bead/emulsion treatment were unsuccessful in preventing recurrent mass development at previous and new sites