Equus Caballus Papillomavirus Type 7 is A Rare Cause Of Equine Penile Squamous Cell Carcinomas.

This research article investigates the role of Equus caballus papillomavirus type 7 (EcPV7) in the occurrence of penile squamous cell carcinomas (SCCs) in horses, a type of cancer traditionally associated with EcPV type 2 (EcPV2). The findings suggest that EcPV7 can also cause these cancers, and its occurrence in oropharyngeal SCCs also indicates a possible contribution in such conditions too.

Research Background

• The research was driven by the prevalence of penile squamous cell carcinomas (SCCs) in horses, often fatal forms of cancer.
• Traditionally, these cancers have been linked with the Equus caballus papillomavirus type 2 (EcPV2), but it was noticed that this type of papillomavirus was not present in all cancer cases.

Study Design and Procedure

• The researchers examined multiple penile SCCs from a 23-year-old standardbred gelding horse that showed histological evidence of papillomavirus (PV) infection.
• Using consensus and specific PCR (Polymerase Chain Reaction) primers, the researchers identified the presence of EcPV7 DNA, but not EcPV2, or any other PV type in the lesions.
• A series of 20 archived samples of penile SCCs were then tested with specific primers to understand the frequency of EcPV7 versus EcPV2 prevalence.

Key Findings

• The study identified that EcPV7 was the only type of PV detected in one of the samples. Both EcPV2 and EcPV7 were found in 5 samples, while only EcPV2 was detected in the remaining 14 samples of penile SCCs.
• EcPV7 DNA was also present in 3 out of 10 archived oropharyngeal SCCs, but always as a co-infection with EcPV2.
• The lesions with EcPV7 DNA did not show any clinical or histological characteristics that differentiated them from those containing EcPV2 DNA.

Implications of the Study

• This study is the first to report the presence of EcPV7 in equine diseases, providing evidence that papillomavirus types other than EcPV2 can cause penile SCCs in horses.
• The research suggests that EcPV7 may cause a subset of these cancers, and implies a potential role for this PV type in oropharyngeal SCCs too.
• These findings suggest that vaccines preventing EcPV2 infections might not be sufficient to prevent all equine penile SCCs due to the potential involvement of EcPV7 in inducing such cancers.