Usually beginning in the horse's frog, canker is a chronic anaerobic infection that is characterized by the proliferation of horn tissue. Other variations of this disease occur in different species including hoof rot in sheep and trench foot in humans. Historically, canker was thought to be caused by poor living conditions such as a wet or unhygenic environment, but many horses that are well cared for can contract canker. In the earlier stages, canker may be confused with an unresponsive case of thrush. Once the disease progresses, the frog area will develop small finger-like papillae made of light brown or grey tissue that resembles cauliflower. A strong fetid odor will also accompany the previous symptoms. If the canker is left untreated during the early stages, horses with this disease will become lame, and the affected tissue will bleed easily and be painful to the horse when touched.
Unfortunately, there is no standard cure for Canker, and many of the treatments used for horses with infection are ineffective. Surgical debridement of the disease has been the most successful treatment. This process usually involves placing the horse under anesthesia because of the pain involved in this surgery. The infected areas can be removed with a sharp hoof knife and a scalpel. Since the hoof will be extremely sensitive after the surgery, this method of treatment also requires cryotherapy to freeze the area that was debrided. Until no traces of the disease remain, the hoof must be wrapped, washed with surgical scrub, and packed with antibiotics daily. On the other hand, many topical treatments are available such as Magic Cushion Extreme and Well-Horse Antibacterial Resin. However, there is no clinic evidence available to support the success of these products. Obviously, the treatment for canker is extremely labor intensive and may not remove the disease. For these reasons, many horses that develop canker are euthanized especially those that do not receive treatment in the early stages of the disease.
Although the horse pictured above does not have canker, this picture demonstrates the stance a horse with canker will assume to relieve the pressure on the frogs of its back feet. This is different from the stance a horse with laminitis that shifts the weight to the heels.