Overview of Ulcerative Dermatosis of Sheep
(Lip and leg ulceration, Venereal balanoposthitis and vulvitis)
Ulcerative dermatosis is an infectious disease of sheep caused by a virus similar to the ecthyma virus. It manifests in two somewhat distinct forms, one characterized by formation of ulcers around the mouth and nose or on the legs (lip and leg ulceration), and the other as a venereally transmitted ulceration of the prepuce and penis or vulva.
The lesion, regardless of location, is an ulcer with a raw crater that bleeds easily, varies in depth and extent, and contains an odorless, creamy pus; it is covered from the beginning with a scab.
Face lesions occur on the upper lip, between the border of the lip and the nasal orifice, on the chin, and on the nose. In severe cases, the ulcers may perforate the lip. Foot lesions are seen anywhere between the coronet and the carpus or tarsus.
Venereal lesions partially or completely surround the preputial orifice and may become so extensive as to cause phimosis. Rarely, the ulcers may extend to the glans penis so that the ram becomes unfit for natural breeding. In ewes, edema, ulceration, and scabbing of the vulva have less serious consequences.
There are no noticeable early systemic reactions. Morbidity rates of 15%–20% are usual, although up to 60% of a flock may be infected. Often, the disease remains unrecognized until the lesions are so advanced that signs of lameness or disturbed urination become apparent.
Diagnosis depends entirely on recognition of the characteristic ulcerative lesion. Differentiation between this lesion and that of contagious ecthyma (see Contagious Ecthyma), which is essentially proliferative in character, is fundamental. In most cases, on removal of the scabs, the lesions of ulcerative dermatosis are crateriform or ulcerative, whereas lesions of contagious ecthyma are proliferative. The question of the similarity of the agents of these two conditions is not clearly defined, but inoculation of sheep previously immunized against contagious ecthyma helps in making a diagnosis. It is also difficult, and in some instances impossible, to differentiate between ulcerative posthitis and vulvitis (see Posthitis and Vulvitis in Sheep and Goats) and ulcerative dermatosis without resorting to sheep inoculation.
Infected sheep should be isolated, and those with genital lesions should not be bred. Recovery takes 2–8 wk and is not greatly influenced by treatment. Therapy is usually not attempted unless the animals are to be bred soon, lip lesions interfere with eating, foot lesions make the animals so lame that they are losing condition, or secondary bacterial infections become severe.
Treatment consists of removing the scabs and all necrotic tissue from the ulcers and applying any one of the following preparations: silver nitrate (styptic pencil), strong tincture of iodine, 30% copper sulfate solution, 4% formaldehyde, 5% cresol (sheep dip), or sulfa-urea powder. Foot and lower leg lesions can be treated with copper sulfate or formaldehyde solutions in footbath troughs.