Papillomavirus Part 4: Equine Canker
From Guest Author Dr. Angelika Schoster, Department of Clinical Studies, University of Guelph.
Equine hoof canker (pododermatitis chronica verrucosa) is described as a chronic, proliferative dermatitis, beginning in the caudal part of the cleft of the frog and gradually expanding to the sole and wall. Equine canker is not lethal in and of itself, but because of where it occurs on the foot, and because it can be so difficult to treat and it recurs so often, it can severely compromise a horse’s ability to do its job (even if that job is just walking around in a field sometimes). The etiology of equine canker has been a topic of discussion for over 50 years, but so far no specific cause for the disease has been found.
Canker is usually diagnosed based on the appearance of the affected horny tissue and a distinctly fetid odour. The definitive diagnosis has to be confirmed by microscopic examination (histopathology) of biopsies collected from the affected tissue.
Treatment of canker has always been a dilemma for veterinarians and farriers because it is so difficult. Treatments used today can range from surgical intervention (removal of the affected tissue) to conservative medical management using topical medications of many different kinds.
The proliferative but non-metastatic nature of canker is similar to that of equine sarcoids. Like canker, sarcoids also tend to be difficult to treat and often recur. Both canker and sarcoids often include a mixture of proliferative and erosive changes in the skin secondary to overgrowth and thickening of the tissues. Due to these similarities, it has been speculated that bovine papillomavirus (BPV) might also be involved in causing canker. A large study in Europe (which will hopefully be published soon) has found evidence to suggest that a variant of BPV-1 plays a role in the development and/or maintenance of canker lesions in horses. Much more study is still needed, but this is another interesting example of how an infectious pathogen may ultimately play a role in a disease that’s origin has remained a mystery for decades.
More information about papillomaviruses is available in our archives.
Image: Severe canker in the frog of a horse's hoof (source: www.answers.com)
