Canker is an uncommon hoof infection that usually occurs in draft horse breeds living in poor sanitary environmental conditions. The infection is caused by an intracellular microorganism that attaches itself to the frog and heel bulbs within the horse's foot. The organism causes abnormal keratin production, resulting in the development of proliferative painful cauliﬂower-like masses and yellow-white tissue along the frog and heel bulbs. Sometimes necrotic areas develop, which produce foul-smelling caseous exudate.
Canker can easily be mistaken for thrush in the early stages of the condition, as it generally originates in the frog of the foot. If canker is left untreated, it will progress to the other parts within the foot and in severe cases, the adjacent hoof wall. Depending on the severity of the infection, the horse may or may not be lame.
Treatment for canker requires surgical debridement of the abnormal tissue, cryotherapy, and thermal cautery in order to fully remove all the abnormal tissue growth. Some veterinarians use a metronidazole/oxytetracycline combination paste following surgery to help with treatment. During recovery and following treatment, horses need to be kept in a clean, well-maintained environment where the feet are kept clean and dry. However, during recovery it is even more important that the hoof is kept protected.