Persistent, widespread papilloma formation on the penis of a horse: a novel presentation of equine papillomavirus type 2 infection
A 9‐year‐old gelding presented with approximately 100 papillomas that covered about 75% of the distal penis. Biopsy was performed, and histology showed evidence of viral cytopathic change and koilocytosis. Polymerase chain reaction using DNA extracted from biopsied tissue amplified equine papillomavirus type 2 (EcPV‐2) DNA sequences. Sixteen months later, the horse was re‐examined and the appearance of the papillomas was unchanged. Equine papillomavirus type 2 DNA sequences were again amplified from both biopsied tissue and swabs of the penis. Papillomavirus was localized to the lesions by immunohistochemistry and in situ hybridization. An examination 2 years after the initial presentation revealed no detectable change in the appearance of the penis. The large number of papillomas and their failure to regress over an extended period support a clinical classification of papillomatosis. To the authors’ knowledge, this is the first report of papillomatosis of the equine penis. This novel clinical manifestation suggests that persistent EcPV‐2 infection is possible in horses. As there is evidence that EcPV‐2 may promote development of equine penile squamous cell carcinoma, understanding the natural history of EcPV‐2 infections may be important in preventing equine penile neoplasia.
Document Type: Research Article
Affiliations: 1: Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Palmerston North, New Zealand 2: Department of Pathobiology and Diagnostic Investigation, Diagnostic Center for Population and Animal Health, Michigan State University, East Lansing, MI, USA
Publication date: December 1, 2011