Canker is a more serous form of thrush and alters the normal growth of the hoof wall. Thankfully nowadays it is rarely seen and is most often seen in horses kept in wet tropical climates, or in large draught type horses. Canker affects the hind legs primarily.
What causes canker?
As for Thrush, Canker is predisposed to long heel conformation, which results in deep sulci (clefts) adjacent to the frog. Damp dirty conditions develop within the sulci allowing bacteria and fungi to invade. This infection then extends from the frog to the sole and wall and in advanced cases to the sensitive underlying tissues of the hoof.
What are the signs of Canker?
Canker generally originates in the frog and can be mistaken for thrush in the early stages. Whilst thrush is limited to the sulci or the base of the frog, canker invades the horn of the frog anywhere throughout its structure. Canker also causes the hoof tissues to grow excessively whereas Thrush destroys them. Lameness is not usually associated with Canker early on but horses may stamp their feet due to the irritation. As the disease progresses, lameness may develop depending on the severity of the condition. The lower limb may also begin to swell as deeper tissues become involved in the condition and become inflamed.
How can I prevent Canker?
This condition can be prevented by good hygiene – daily cleaning of the stable and regular foot care and inspection. Regular attention from a farrier ensures the development of long heels is avoided and also to keep the frog healthy. It is also important that your horse has regular tetanus vaccinations as thrush can allow tetanus to infect your horse. Advice on vaccination can be sought from your veterinary surgeon.