Also Known As
chronic hypertrophy, necrosis of horn-producing tissues
Canker in horses is a chronic enlargement or increase of the horn producing tissues in the equine hoof of the horn-producing tissues of the foot. The disease generally originates in the frog, but if left untreated, spreads to the adjacent sole, bars, and hoof wall. Canker is characterized by numerous small finger-like papillae of soft off-white material that resembles a cauliflower-like appearance. Cancer starts out looking very similar to thrush, but soon distinguishes itself by color and odor.
The microorganism associated with canker causes abnormal keratin production, or overgrowth of the horn. This excessive proliferation occurs underneath the horn, as the infection spreads throughout the epithelial layer.
Commonly, an affected horse will have white or gray matter that is moist and spongy appearing in the sulci region (grooves on either side and in the center of the frog) of the hoof. This characteristic growth’s appearance has been described as similar to wet cauliflower with cottage cheese like exudates. If there is extensive infection, heat might be felt in the hoof, but usually only in extreme situations.
Generally, canker can be diagnosed based on the appearance of the tissue and foul odor, but the definitive diagnosis is achieved via biopsy. Several anaerobic bacteria are usually observed in the layers of epidermis of the frog.
- Gray or white matter on the hoof
- Thickening of the tissue on the frog
- Foul smell
- Holding the hoof off the ground
- Unwillingness to stand or walk
The cause of canker is unknown, although researchers have found that it occurs when there is a lack of oxygen to the hoof or more specifically the frog. It appears that many factors are involved in cases of development of canker in horses.
The best way to prevent canker is to keep bedding clean and dry and pick out the horse’s feet often. When a horse becomes sensitive to having his feet touched, has discharge from the foot area, or has development of strange-looking tissue, call your veterinarian immediately. Canker is most easily treated when it is caught early. Canker is often chronic, and relapses may occur after treatment. Your veterinarian and farrier are the go-to-team for early diagnosis and prevention of canker in your horse.
Treatment requires sharp debridement down to normal tissue, attempting to maintain any normal epithelium. All loose horn and affected tissue should be removed. After debridement, an antiseptic or antibiotic dressing should be applied daily; good results have been reported using a solution of 10% benzoyl peroxide dissolved in acetone. Metronidazole is commonly applied topically with the benzoyl peroxide/acetone treatment. Keep the infected site open to the air and apply an antibiotic and microbial cream. Be sure to keep the area clean and dry.
Depending on conditions, the affected area may be covered with a clean, dry bandage. A waterproof bandage is preferable. All bandages must be checked and changed regularly while the area is healing.
Limit exercise and typical daily routines while healing. This will give your horse a chance to rest and heal more quickly. If you notice that the affected area is staying moist or other hooves are beginning to look suspicious, call your veterinarian and have your horse re-checked.
A clean, dry wound environment must be maintained to allow healing, which may take weeks or months. Close attention is required over the healing period; if any questionable areas appear, they must be aggressively addressed.
Prognosis is always guarded with canker and daily foot care for the horse is essential to the successful treatment of this disease process. Horses have variable responses to treatment, with some cases healing within a week to 10 days and others lasting for months. Once the tissue is healed, the disease rarely recurs. However, if treatment is halted before healing is complete, canker may return - a trait that previously led many to believe it was a cancerous disease.