ulcerative posthitis (pizzle rot or sheath rot) | ulcerative dermatosis (lip and leg ulceration, ovine venereal disease) | caprine herpes
Introduction: Ulcerative posthitis (sheep and goats), ulcerative dermatosis (sheep), and caprine herpes (goats) are all problems that can cause lesions on the genitals, legs, feet, eyes or face of the affected animal. Although the clinical signs are similar, they are caused by different organisms and situations.
Ulcerative Posthitis (Pizzle rot or sheath rot)
Causative Agent: Pizzle Rot is most often caused by an interaction of the bacterium Corynebacterium renale and excess urinary urea. Excess urea accumulates as a result of too much protein in the animal's diet. C. renale converts excess urea into ammonia, which damages mucosal surfaces. This problem affects mostly male sheep, but has shown up in castrated goats as well.
Although the bacterium C. renale is common and can be transmitted by asymptomatic (not showing signs of disease) ewes, does, cows and insects, ulcerative dermatosis does not develop until the animal consumes increased protein. This is common in the spring when animals graze high protein feed, or in animals, such as goats for mohair production, that have higher protein requirements. It also turns up in pre-sale animals receiving more protein for finishing and in confinement settings where the bacterium is able to survive longer. Pizzle rot has also been associated with excessive hair at the preputial orifice (opening to the prepuce), causing the area to remain moist with urine, prolonging urea contact with bacteria. Because castrated animals have a decreased ability to extend the penis and tend to urinate in the sheath, castrating sheep and goats before puberty is a pre-disposing factor.
Clinical Signs: The affected animal will strain during urination, the prepuce will swell and occasionally there will be narrowing of the opening to the prepuce. Necrosis and ulceration of the preputial mucosa develops as well. Severe cases may cause the animal to suffer abdominal discomfort, colic and/or a stiff-stilted gait. The urine is usually malodorous and can appear thick or semi-solid.
There are similarities between pizzle rot and ulcerative dermatosis (which is a viral disease) causing confusion in the diagnosis. However, the two problems can be distinguished by the locations of the lesions they cause. Ulcerative dermatosis can affect both male and female animals, causing lesions on the penis, sheath, vulva, legs, lips and eyes of an affected animal.
Treatment: The first step is to reduce the protein content of the diet. (The condition has shown up as soon as 2 weeks after protein intake has increased. Diets as low as 12% protein have been associated with this condition, but affected animals are usually taking in more than 12% protein.) When protein intake cannot be lowered, urine acidifiers, such as ammonium chloride, and/or antimicrobial agents, such as chlortetracycline, may help.
Next, removing necrotic tissue and applying antiseptics or antibiotics, such
as iodine or triple antibiotic ointment, to skin lesions can also help. The
sheath may need to be irrigated and if the opening to the prepuce is scarred to
the point that normal urine flow is partially or completely stopped, the sheath
should be opened using surgical procedures. Placing the sheep or goat on a
broad-spectrum antibiotic such as tetracycline is another good practice. Shaving
the preputial area of hair and burning the removed fiber can help in prevention.
Ulcerative Dermatosis (Lip and leg ulceration, ovine venereal disease)
Causative Agent: This problem in male and female sheep is caused by a Parapoxvirus, which gains access into the affected animal through cuts, scrapes, shearing, and breeding trauma. It has also been associated with abrasions that are common around the vulva and penis caused by breeding unshorn sheep.
Clinical Signs: Ulcerative dermatosis is an infectious disease of sheep characterized by crusted ulcers on the skin of the face, feet, and external genitalia. The crusty lesions appear to be circular and range from 5 mm to 30 mm in diameter and 3 mm to 5 mm deep on the prepuce, penis, vulva, nostrils, eyes, legs and hooves. These lesions may contain a thick, odorless, pus-like secretion.
Treatment/Prevention: Astringents or antibiotic ointments can be applied
to the lesions in an effort to reduce pain. The virus should run its course in 2
to 6 weeks. Affected animals should be isolated until their lesions are healed.
All new animals should be quarantined up to 4 weeks before introduction to the
rest of the flock. Good facility hygiene is another important preventative.
Caprine Herpes (Bovid herpesvirus 6)
Causative Agent: Caprine herpes (CHV) is caused by a herpesvirus that is venereally transmitted in goats. This virus has been identified in cases found in New Zealand, Australia, the United States and Switzerland, especially in feral goat populations. It is considered an emerging disease of potential importance in goats. There are both respiratory and viremic kid forms as well.
Clinical Signs: Any goat of breeding age can be infected with the virus and can be carriers without showing any signs of the disease. When signs do show, they consist of an inflammation of the vagina and vaginal opening in the female (vulvovaginitis). There is a swelling and reddening of the vulva with loss of the membrane lining the vagina and its opening. There is usually a thick yellow discharge. The disease has been associated with abortion, both with and without vulvovaginitis. In the male there may be similar lesions on the penis (balanoposthitis) and possibly a preputial discharge.
Disease Transmission: Generally the disease in introduced to a flock/herd by an infected animal at mating. The disease then seems to spread fairly rapidly to a number of susceptible animals. Although lesions heal, it is likely that many animals remain infected for life and are capable of transmitting the disease at mating to other susceptible animals. However, kids do not seem to acquire infection by birth, nursing or close contact.
Treatment: There is no effective treatment at this time. Infected does and bucks usually heal spontaneously within 2 weeks; however, recurrent lesions are possible. Once CHV is identified in an animal, the rest of the flock/herd should be suspected as being infected. However, the CHV virus can only be diagnosed with a blood test. The only way to eradicate the disease from a farm is to eliminate the affected animals and start again. Sometimes secondary bacterial infections occur with CHV. They can be controlled by administering antibiotics when an animal with the disease has been diagnosed.
Prevention: There is no vaccine, so prevention involves blood testing all animals before introducing them to a clean flock/herd. This especially applies to animals introduced for breeding purposes. Kids should be separated from older animals before they become sexually mature and maintained as a separate group. Culling all positive animals upon detection is essential.