Equine canker is defined as chronic hypertropic, moist pododermatitis that usually affects the frog, bars and adjacent sole of the foot. It often originates in the frog and can be mistaken for thrush in the early stages. Canker is characterized by numerous small finger-like papillae of soft off-white material that resembles a cauliflower-like appearance. The condition is accompanied by a foul odor and a caseous white exudate that looks like cottage cheese. The affected tissue will bleed easily when abraded. Varying degrees of lameness will be present depending on the extent and depth of the infection. Canker can occur in one foot or multiple feet may be involved. The disease is commonly seen in draft breeds but can affect any breed or sex. It appears to have an affinity for wet or moist unhygienic conditions.

Equine Canker
Note: the vegetative appearance of the frog

A presumptive diagnosis of canker should be confirmed with a biopsy. Care must be taken to remove the superficial necrotic tissue before the biopsy is taken from the margin of the lesion. The biopsy should include both normal and abnormal tissue. A 6 mm biopsy punch works well.

Treatment

Canker always carries a guarded prognosis but recently this author has been successful with the following approach. Careful, thorough debridement of the affected tissue is required and is the most important aspect of therapy. The horse can be placed under general anesthesia or regional anesthesia can be used with the horse standing. A tourniquet placed around the fetlock is essential to provide a bloodless field in which to work. Debridement is best performed using a sharp hoof knife or loop knife. All abnormal tissue is removed down to normal corium. A clear demarcation will be seen between normal and abnormal tissue. Next cryotherapy is used to freeze the area that has been debrided. The area of the foot that has been debrided will be soft and pliable. Freeze this affected area until the tissue becomes hard (known as hard freeze), allow the area to thaw and then repeat the freeze once more.

Following the above procedure, the horse is placed in dry bandages. It is also important to keep the animal in a dry environment. The bandages are changed every 2 or 3 days. Topical treatment is optional. If a topical ointment is used, I would suggest mixing metronidazole (an antibiotic) with betadine ointment. A shoe with a treatment plate can also be used but it is sometimes hard to keep the foot as dry as necessary with this method.

The freezing procedure should be repeated if there is any sign of reoccurrence of the disease.

A commitment is necessary from the owners, as aftercare will take several weeks until the affected tissue is cornified.