Page 92 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Musculoskeletal system: 1.3 The foot 67

VetBooks.ir (2) thrush is confined to the frog and paracuneal Furthermore, bovine papilloma virus DNA has
been identified in 100% of canker lesions in
sulci, whereas canker may extend to any part of
the hoof; (3) horses with thrush are less likely to
be lame; and (4) remedies that usually cure cases of one study and was absent in all control samples.
However, it has not yet been established whether
thrush frequently fail to improve canker. canker in fact represents one or more disease pro-
cesses or aetiological agents.
Management
Thrush is effectively treated with debridement of Clinical presentation
ragged and undermined frog, transferring the horse The duration of the disease is usually chronic, over
to hygienic and dry conditions, improving daily several weeks to months. It may affect one or more
foot management and applying topical antiseptics feet. Canker has a characteristic proliferative appear-
and astringents (e.g. povidone–iodine, 2% tincture ance from which extend finger-like projections, and
of iodine or proprietary preparations of formalin it is usually associated with a yellow, creamy exudate.
[but formalin in its aldehyde state is best avoided]). The lesion is typically located on the frog, but may
Corrective trimming and shoeing are essential have extended to involve any other part of the hoof.
where there is poor foot conformation. Daily foot Palpation of the affected area is likely to elicit a pain-
care should be considered and improved if neces- ful response. Early in the course of the disease the
sary and the ground and stable bedding conditions horse may be sound or slightly lame, but as the dis-
changed if appropriate. ease becomes more advanced the lameness becomes
progressively worse.
Prognosis
The prognosis is almost always good. Horses with Differential diagnosis
narrow frogs and deep sulci are likely to experience Thrush.
recurrence if they have to stand on moist unhygienic
surfaces. Diagnosis
Diagnosis is usually based on the physical appear-
CANKER ance of the foot (Fig. 1.111), but a biopsy and histo-
pathology are required for confirmation. Canker is
Definition/overview frequently mistaken for thrush early in the course
Canker is defined histologically as a chronic prolif- of the disease but is much less common. There are
erative pododermatitis.

Aetiology/pathophysiology 1.111
The disease classically starts in the central or par-
acuneal (collateral) sulci and then rapidly spreads
to the crura of the frog. It may extend to the sole
or bulbs of the heel and occasionally even to the
walls of the hoof. Canker classically occurs in the
hooves of horses that are standing for prolonged
periods on a wet ground surface that is contami-
nated with faeces. The aetiology and pathogenesis
of canker are unknown, but anaerobic bacterial
infection affecting the germinal layer of the epi-
thelium has been hypothesised in the literature.
Spirochaetes have been demonstrated to be pres-
ent in biopsy samples taken from horses with can-
ker, but as yet it is undetermined whether they are Fig. 1.111 Canker. Extensive moist proliferation of
a causal/partially causal or a commensal organism. the epidermis of the crura and sulci of the frog.