Page 1272 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Skin 1247

VetBooks.ir cell division. As secondary inflammatory changes 12.40
occur around them, they develop into typical
tumours of the skin, which may present as enlarged
nodules or verrucous forms, or develop ulcerative
changes and necrosis.
Swellings also include urticarial swellings,
abscesses and body swellings such as hernias and
cysts. Urticaria is covered later in this chapter (see
p. 1281). Abscesses are localised fluid- to solid-filled
lesions. They are the result of inflammatory changes,
usually related to trauma and/or infection, and con-
sist of dead cells, debris and local tissue components Fig. 12.40 Equine molluscum contagiosum is due to
that have liquefied through proteolytic and histo- a poxvirus occurring around genital organs of mares
lytic enzymes. Although usually related to infection, and stallions and presents with small papules and a
abscesses can be sterile. waxy skin surface. (Photo courtesy DW Scott; reprinted
Tumours, nodules and swellings tend to be pri- from Pascoe RR and Knottenbelt DC (1999) Manual
mary disease sites and in horses are infrequent mani- of Equine Dermatology, WB Saunders, with permission)
festations of systemic disorders. The major disease
considerations in establishing a differential diagno-
sis are physical causes, infectious diseases, hypersen- EQUINE VIRAL ARTERITIS (EVA)
sitivity reactions, sterile inflammatory diseases and
neoplasia. Definition/overview
Injuries to the skin and underlying tissues may EVA is a viral disease associated with abortion,
result in superficial trauma to the epidermis right infertility and skin disease. Some strains are rela-
through to joint, bone and muscle injury. This is tively avirulent and infection may go unnoticed and
manifested by an alteration in the normal contour of undiagnosed (see Chapter 2.1, p. 454).
the skin and may lead to diagnostic confusion among
cellulitis, haematoma, bursitis and hernias. PAPILLOMATOSIS
Bruising is extravasation of blood into the der-
mis and epidermis without severe dislocation of Definition/overview
the external epidermal layer. Haematoma involves Papillomatosis is a viral skin disease characterised by
the rupture of blood vessels in subcutaneous tis- small warts on the nose, lips, around the eyes, inside
sues leading to extravasation of blood into the the ear and very occasionally on the neck and limbs.
interstitial tissue. Cellulitis is extravasation of cel-
lular fluid into tissue spaces, which may or may not Aetiology/pathophysiology
be infected. Seven Equus caballus papillomaviruses (EcPV) have
been described in horses and each has been associated
INFECTIOUS CAUSES – VIRAL with one of three different conditions: (1) EcPV1
with classical warts; (2) EcPV2 and EcPV7 with
EQUINE MOLLUSCUM CONTAGIOSUM genital plaques, carcinoma in situ and SCCs; and
(UASIN GISHU DISEASE) (3) EcPV3–6 with aural plaques. Additionally, aber-
rant species infestation with bovine papillomavi-
Definition/overview ruses (BPV1 and BPV2) induces equine sarcoids.
This is a mild contagious cutaneous infection caused Transmission can occur via direct contact with an
by unclassified poxviruses. Lesions may occur on the infected horse, indirectly through contaminated
penis, prepuce, scrotum, mammary glands, thighs, fomites, sexual transmission or trauma including
axillae and muzzle (Fig. 12.40). insect bites.