Canker is a chronic hypertrophy and apparent suppuration of the horn-producing tissues of the foot, involving the frog and the sole. The cause is unknown. Although frequently described as a disease seen in animals kept in moist or unsanitary environments, it is also encountered in well-cared-for animals. The disease can be observed in both front- and hindfeet. It most commonly starts in the caudal frog, where the affected area consists of an inflamed granulation tissue with proliferative epithelium, often appearing as fronds. The affected tissue is commonly covered by caseous exudate, which may be foul smelling. The surface of the lesion is irregular, with a characteristic, cauliflower-like vegetative growth. The disease process may extend to the sole and even to the wall, showing no tendency to heal.
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. 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.