Page 1308 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Skin 1283

VetBooks.ir inclusion in an ASIT treatment set should be con- then deposited within vessels, activating complement
and inducing inflammatory mediators. Inflammatory
sidered. Long-term use of corticosteroids and/or
antihistamines may be required in some situations.
affect the endothelial cells and play a role in the man-
Oral administration of dexamethasone at the lowest mediators, adhesion molecules and local factors may
possible dose on an alternate-day basis or oral anti- ifestations of this disease. Exacerbation of lesions by
histamine (cetirizine hydrochloride, 0.2–0.4 mg/kg photoaggravation is common.
q12–24 h) are options. Antihistamines should be
used daily for at least 2 weeks to determine their Clinical presentation
efficacy. Doxepin (0.5–0.75 mg/kg q12 h) is a tricy- The most common sites of vasculitis are the coronet,
clic antidepressant with antihistaminic activity that pastern, fetlock (Fig. 12.88), lips and periorbital tis-
has been used successfully for patients that do not sues. Oedema, erythema, necrosis and ulceration are
respond to cetirizine. seen. Pyrexia, depression, anorexia and weight loss
may also be present. There is no pruritus or pain,
VASCULITIS except in early crusts.

Definition/overview Differential diagnosis
Vasculitis is an uncommon disorder characterised Equine granulomatous enteritis; equine leucocyto-
by purpura, oedema, necrosis and ulceration of the clastic vasculitis (Fig. 12.89); greasy heel.
lower limbs and oral mucosa.
Diagnosis
Aetiology/pathophysiology The clinical appearance is suggestive. Biopsy is used
Vasculitis is thought to be mediated by immune com- for confirmation. Diagnostic biopsies are best taken
plex deposition. In this form of vasculitis, circulating in the first 24 hours of a fresh lesion occurring.
antigens in the body (possibly triggered by factors
such as medications, infections [e.g. Streptococcus Management
equi, 2–4 weeks after infection], food antigens, envi- If possible, the underlying disease should be treated.
ronmental allergens or neoplasia) induce antibody Provided the diagnosis is very rapid, oral prednisolone
formation. These antibodies bind to the circulating (1–2 mg/kg) should be given twice daily until regres-
antigen and create immune complexes, which are sion occurs, and then reduced to the lowest possible

12.88 12.89

Fig. 12.88 Vasculitis following
S. equi vaccination during a
severe outbreak of strangles
on a Standardbred farm. This
yearling had lesions on all four
pasterns and fetlocks.

Fig. 12.89 Leucocytoclastic
vasculitis in a mature horse,
with swelling on the black areas
of the limbs. The cause was
undetermined.