Treating Prolific Equine Canker

In most texts canker is described as a chronic disease, more commonly found in draught type breeds and usually in the hind legs. The pictures at right show a progression of treament for canker. Historically more prevalent in untreated cases of thrush, greasy heel or a puncture wound. Canker was found more in damp places with a higher number of offending micro-organisms such as in cities or dirty stables. For legal and veterinary terms a horse with canker is unsound. Simply it could be described as a degenerative dermatitis. The lamella become tumefied and swollen and become soft and spongy. Left untreated it underruns the entire sole and can even travel up underneath the walls. Adams describes it as “chronic hypertrophy of the horn producing tissues of the foot” hypertrophy being excessive growth due to increase in size of cells. This is why Butler describes it as hoof cancer. This overgrowth of tissue degenerates and then becomes contaminated with a wide variety of germs. There is always a very offensive smell present, an un mistakable odour. The exact cause of canker is unknown. Horses with systemic or constitutional upset are more susceptible. Butler believes the cause to be “constant contact to strong ammonia compounds (urine and faeces) which irritate the sensitive structures and cause benign and possibly malignant growths to be produced.” Adams agrees with this theory and adds that “the specific cause is believed to be an infectious process, agent unknown”. Due to the difficulty and length of time taken to treat canker the disease is generally considered incurable. If the disease is discovered before the foot has suffered extensive damage the prognosis is favourable. However the prognosis is guarded if the sensitive structures of the hoof are involved. Cleanliness is the most important part of treatment, when treating topically the area should be cleaned and the treatment packed on and bandaged firmly Canker is a disease that has defied the attempts of veterinary surgeons to provide a specific remedy and affect a cure. Some products that have been used to treat canker are:

• Penicillin – systemically and topically

• Equal parts of phenol and iodine.

• 10 % formalin solution

• 10-15% Sodium sulfapyridine solution

• lotion combining antibiotics and corticosteroids.

• Metronidazole

• Stockholm tar, lard and sulphuric acid applied fresh daily.

• Phycofixer – the latest wonder drug ( phycofixer is composed of ketoconazole and rifampin, you just store it at room temperature. It is a liquid that should be applied topically daily. Dr Murray Brown of the University of Florida is the man behind the drug).

Much work has been done on studying canker but a specific casual organism has not been identified. Organisms that have been isolated infesting cankerous tissue are Spirochaeta (spiral bacteria with a flexible body and no rigid wall), gram positive bacteria. Various fungus and even protozoa’s. Treatment at MBHCC Patience and perseverance are imperative. Daily treatment is necessary for success. Step 1 the affected feet must be kept dry and sterile. Step 2 is to kill the offending and invading bacteria/fungus/organisms Step 3 is to slowly resect and burn back the deformed growing horny tubules. Step 4 to encourage growth of new normal tissue again. 1. The affected feet must be kept dry and clean and as sterile as possible. Stalls must be kept dry and free from soiled matter. Lime plays an important role. We kept the horse in a rubber laneway and cleaned the laneway twice daily. During wet weather a firm floored stable dusted with lime was used. Later during the treatment the affected feet were bandaged and or booted and the horse was allowed out to pasture. Bandages boots were not left on 24/7. Movement and exercise also play a role in healthy regeneration of tissue. 2. Soaking daily in a strong anti bacterial/ anti fungal/ antiviral solution. We have used Virkon with great success. A cheaper option in Phenyl (garbage bin sanitiser). 3. Removal of the diseased material and cankerous growth – This is often similar in histology to proud flesh and bleeds profusely. Surgical removal is the current veterinary recommendation; however there is documentation to show that this is often not successful. It seems that such disturbance of the tissues only cause the regrowth to be even more rapid. It is also very hard to slow the profuse bleeding. It is also very hard to fully resect into the corium and determine which the offending cells are and which the normal cells are. The rest of the unaffected hoof and frog should be trimmed back to their normal shape. We have found gradual resection in combination with chemical burning to be successful. In a dry environment we have used a twice daily application of equal parts yellow lotion, copper sulphate and DMSO. Applied with a toothbrush and generously dusted with lime. Once we had burnt back the externally evident canker with this treatment we changed to applying my own home made petty spurge (Euphorbia peplus) ointment, packing with swabs to apply pressure and finishing off with a baby nappy and bandage. (Still in combination with daily soaking). The difficulty we found is when to know all affected tissue (in underrun sole) has been removed. 4. Optimum body health is important to healing, a good diet, lots of movement and a positive state of mind is all important. To promote healthy new growth of tissue we are using a combination of ti tree oils, Manuka honey and calendula. Hardening and drying agents may be used to help harden up the hoof tissue, however the infection must be treated first.. We do not want to lock any anaerobes back in so they can thrive again ! Prevention is far better than cure – regular stall and hoof cleaning is important in stabled horses.