Canker is now rarely seen but is a serious infection of the horn
of the foot, which results in the formation of a soft, moist,
disintegrating growth of horn. It most commonly affects the hind
feet and is most often seen in horses kept in wet tropical
climates, or in large draught type horses. It is predisposed by
long heel conformation which results in deep sweaty sulci
adjacent to the frog.
What causes canker?
Infection is most commonly associated with bacterial and
sometimes fungal invasion of the epidermal horn of the foot,
starting around the frog and extending to the sole and wall. In
advanced cases infection may enter the underlying sensitive
laminae of the hoof.
How is canker diagnosed?
In the early stages, a foul-smelling, moist, vegetative mass of
horn is seen, although lameness is rarely encountered. The
characteristic, fragile, fronds of horn growth start at the back
of the frog and are sometimes covered with a crusty overgrowth.
In advanced cases, a cauliflower-like proliferative growth may be
seen along the heels, bars, sole and hoof wall and lameness may
develop at this stage. Affected horses may stamp the affected
foot, reflecting irritation. If deeper tissues are involved,
there may be swelling of the pastern and lower limb. Radiographic
(x-ray) examinations may be required to determine the extent of
the damage to the bony structures of the foot and the collateral
How is canker treated?
Your veterinary surgeon will thoroughly clean the sole, sulci and
frog, debriding and curetting (removing) all abnormal, dead and
infected tissues, under general anaesthesia, if necessary. The
clean wound is then packed with sterile gauze soaked in
antiseptic solution (e.g. dilute povidone iodine) and the foot is
bandaged. The horse will often require treatment with
antibiotics, active against both aerobic and anaerobic bacterial
infections and so the cleaned area may be swabbed, to determine
which bacteria or fungi are present, in order to determine the
most appropriate antibiotic or antifungal treatment to use.
Lockjaw antitoxin must be given, if the horse is not fully
vaccinated up to date or if vaccination status cannot be
Afterwards, you must ensure clean, dry stable conditions and the
bandage and antiseptic gauze pack must be changed every 2-3 days
until there is no more discharge and the tissues appear healthy
and healing. The horse must be kept out of wet and muddy
conditions until the wound is completely healed. When recovered,
the affected foot should be re-shod and any hoof malformation
should be gradually corrected.
How can canker be prevented?
Prevention is always better than cure and canker can be avoided
by good stable management, and regular foot care and inspection.
You should stable your horse in clean dry conditions and you
should exercise your horse regularly. Your horses' feet should be
regularly trimmed and shod, in order to avoid the development of
long heel conformation and to keep the frog healthy.
The prognosis for complete recovery for true canker is always
more guarded than for thrush. The prognosis for complete
resolution is poor for long-standing cases with spread to the
sole involving deeper tissues, because recurrence is common,
especially in those horses with hoof deformity.
Make sure that your horses are always fully vaccinated against
lockjaw, an invariably fatal infection which can gain access
through hoof injuries.