Page 93 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

68 CHAPTER 1

VetBooks.ir several features that help differentiate thrush from soaked and dried, has been successful. Alternatively,
topical dressings saturated with 10% benzoyl per-
canker. In thrush the lesion is degenerative, whereas
in canker it is proliferative. In thrush the disease is
Several other topical treatments have also been tried
confined to the frog, whereas canker may spread to oxide in acetone have also been used successfully.
other parts of the hoof. Both may cause lameness, with varying success including chloramphenicol and
but this is more common in canker. Traditional topi- fungicides. More recently, based on the potential
cal medications that are effective against thrush are role of bovine papilloma virus in the pathogenesis
ineffective against canker. of the disease, topical cisplatin in a cream has been
used successfully. Systemic use of antibiotics with an
Management anaerobic spectrum of activity (e.g. metronidazole
Treatment comprises a combination of surgical or penicillin) are unlikely to be successful as a sole
debridement and medical therapy. Prior to debride- therapy but may be useful as an adjunct to local ther-
ment the foot should be trimmed to ensure maximal apy. Additionally, systemic steroids have been used as
width between the heels and, if necessary, part of the an adjunct to therapy, with apparent success without
bars can be removed to open up the sulci as much documented complications.
as possible. This maximises drainage and limits the In uncomplicated cases the lesion is dramati-
crevices in the sulci within which the causative agent cally improved within 2 weeks and resolved within
can linger. Debridement is usually satisfactorily per- 4 weeks. In complicated cases where there is a res-
formed in the standing sedated horse using perineu- ervoir of the causative agent in a protected location
ral analgesia of the palmar nerve at the level of the in either the hoof or the environment, recurrence is
proximal sesamoids, but difficult horses may require common.
general anaesthesia. The goal of surgical excision of
the proliferative tissue is to preserve as much of the Prognosis
germinal layer of the epidermis as possible so that The response to treatment in this disease is highly
healing occurs as a partial-thickness wound by epi- variable and, therefore, the prognosis must always
thelialisation without the formation of fibroplasia. initially be guarded. A cautious long-term outlook
More aggressive debridement that removes signifi- is advised because it is not currently known whether
cant amounts of the germinal epithelium results in individual animals may have a predisposition towards
healing by fibroplasia and epithelialisation, which developing this disease.
delays healing without improving results. The sur-
face tissue may be removed with a hoof knife, a scal- LAMINITIS
pel or laser, but the more intricate debridement is
best performed with a rongeur. Alternatively, after Definition/overview
gross debridement, sterile maggots may be used Laminitis is a disease in which a series of pathophys-
for the more detailed debridement. A tourniquet iological events cause injury to the dermal and epi-
is usually unnecessary if debridement is limited to dermal lamellae (Fig. 1.112). This in turn weakens
the tissues superficial to the germinal epidermis, the attachment between the lamellae and, at its most
but is necessary if more extensive debridement is to extreme, causes separation of the hoof capsule from
be performed. Many topical medications have been the underlying tissues. Laminitis has been defined
used in the treatment of canker. A 2–5% suspen- as acute if it is within 72 hours of onset of clinical
sion of metronidazole in saline or a paste made from signs and has not been accompanied by displacement
crushed metronidazole tablets and saline applied as a of the distal phalanx. It has been defined as chronic
wet-to-dry dressing after debridement is frequently once the distal phalanx has displaced in relation to
effective. In refractory cases, 0.05% enrofloxacin or the hoof capsule (regardless of duration). Laminitis
clindamycin in Tricide (Molecular Therapeutics that is present for more than 72 hours’ duration and
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LLC), applied either as a wet-to-dry dressing or as is not accompanied by displacement has been defined
a dry-to-dry dressing after the dressing has been as subacute. Clearly, the division between these