This moderately contagious disease is caused by Corynebacterium renale , a gram-positive, diphtheroid bacterium capable of hydrolyzing urea. When protein intake is high, urinary urea concentration increases. Hydrolysis of urea by C renale results in local production of large quantities of ammonia, which is believed to irritate the penis, lamina interna of the prepuce, and skin surrounding the preputial orifice. The condition is more common in male castrates, probably because of the hypoplastic nature of the penis, exacerbated in some cases by failure of penile-preputial separation that leads to pooling of urine in the prepuce. If preputial hair is cut too short or becomes caked with mud or organic matter, drainage of urine away from the preputial orifice (normally facilitated by this hair) is impaired, and ulcerative lesions may develop.
In mild cases, signs are limited to swelling of the prepuce. In severe cases, swelling and inflammation interfere with urination and result in straining. Ulcers and scabs may be found around the preputial orifice, on the lamina interna of the prepuce, and on the shaft of the penis. Urine and exudate may accumulate in the prepuce. The condition may cause severe discomfort. If the preputial orifice or urethra is occluded, affected animals may die.
Ulcerative posthitis (sheath-rot, pizzle-rot) is a moderately contagious disease associated with high protein diets and a concurrent Corynebacterium renale bacterial infection of the prepuce. A diet of 18 percent or more protein results in alkaline urine containing large amounts of urea. Corynebacterium renale converts urea to ammonia in the sheath, which irritates the tissues. Ulcers or sores form, usually at the prepuce opening. Scarring of the prepuce can result from prolonged infections. The infection can be spread to ewes at breeding. Treatment of this condition can be accomplished either medically or surgically. Affected animals need to be identified before the breeding season, so that either treatment and control regimes can be implemented or new breeding animals obtained.
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