Diseases of Bovine Teats and Skin
Bovine herpesvirus II and IV (BHV-II, BHV-IV) can cause an acute, ulcerative condition of teat and udder skin of dairy cows that is often referred to as bovine ulcerative mammillitis. BHV-II can occur sporadically or in outbreaks that often have a seasonal association with cold weather and may result in reduced milk production and increased susceptibility to bacterial mastitis.
Clinical signs range from relatively mild, small plaques of edema to severe ulceration. Early signs may vary, but the lesions often begin as one or more thickened, edematous plaques of varying size on the skin of one or more teats. Vesicles develop and may rapidly rupture, leaving a raw, ulcerated area that becomes covered with a dark-colored scab. The scabs tend to crack and bleed, especially if milking is attempted. The lesions are of variable size and can include much of the teat wall and orifice. Teats are generally painful, and affected cows often resist milking, leading to development of mastitis. The greatest incidence is often seen in first-lactation cows, but previously unexposed cows of any age are susceptible. Severe lesions may take several weeks to heal.
Diagnosis is based on clinical signs and confirmed by histopathology or by virus isolation from early lesions. Treatment is directed toward supportive care, because there is no effective therapy for this virus. The use of iodophore-containing teat dips with added emollients may help to inactivate the virus. It is important to isolate affected cows and to use separate milking equipment. Affected animals should be segregated to prevent spread among all animals. The use of separate milking equipment; clean, single-use towels to dry udders; and clean gloves for milking personnel help to prevent spread of the agent to susceptible animals.
Pseudocowpox is a condition of teat skin caused by a poxvirus that results in a characteristic horseshoe-shaped lesion or scab (see Pseudocowpox).
Several strains of bovine papillomavirus (BPV1, BPV5, BPV6, BPV9) cause the development of papillomas or fibropapillomas on teats. In some herds, pale, smooth, raised lesions develop frequently on teat skin and may persist indefinitely without causing problems. In other instances, filamentous or frond-like lesions develop at the teat orifice and interfere with milking. Bovine warts are spread by direct or indirect contact, and bovine papillomavirus DNA has been identified in blood, milk, urine, and other biologic fluids obtained from infected animals. Diagnosis is usually made presumptively based on examination of the lesion and exclusion of other causes. In many instances, treatment of warts is not necessary, but frond-like lesions that interfere with milking may require excision. The use of autogenous vaccines and virucidal teat dips may be recommended in herd outbreaks.
The development of raised smooth or rough rings at the teat ends of lactating cows is a common occurrence and is associated with the keratin dynamics of the streak canal. Teat ends affected with hyperkeratosis may progress from smooth, doughnut-shaped lesions that do not affect milking to severely hyperkeratotic rings with radial cracks. When teats are severely affected, the ability to properly sanitize teat ends before milking may be compromised. Diagnosis is usually made by clinical examination of affected teats. The degree of hyperkeratosis is often characterized by scoring teat ends using the following scale: 1) no ring, 2) smooth ring, 3) rough ring, and 4) very rough, cracked ring.
The cause of hyperkeratosis is multifactorial; thus, prevention is directed toward a number of potential risk factors. Hyperkeratosis is often associated with cold weather, probably because of changes in peripheral circulation. Risk factors for development of hyperkeratosis include incorrect use of teat sanitizers, exposure of wet teats to cold weather, improper milking machine settings leading to overmilking, inadequate massage phase during milking, and inadequate milk letdown. After underlying risk factors are addressed, affected teats generally recover over several weeks or over a dry period.
Dermatitis of the udder has a number of causes, including chemical irritants, sunburn, and bacterial infection. The udder can be exposed to chemical irritants from bedding additives (eg, some types of limestone) or chemicals used during milking. The irritation usually resolves after removal of the offending substance, but gentle udder washes and use of emollient products can accelerate healing. Udder impetigo (udder acne) is a bacterial dermatitis characterized by development of small pustules on the skin of the udder and teats. Staphylococci usually can be isolated from the pustules. Treatment of udder impetigo consists of clipping hair from the affected area and washing the skin thoroughly each day until the condition resolves.
Teat skin can chap and crack when wet teats are exposed to cold winds or frozen bedding areas. Exposure of wet skin to subfreezing temperatures may result in frostbite. Skin affected by frostbite becomes swollen and discolored and ultimately develops a leathery texture. In severe cases, the teat skin may slough. Frostbite is best prevented by ensuring that teat skin is dry before allowing cows access to housing areas or pastures during periods of temperatures <0°F. Care should be taken to ensure that all bedding areas that contact teat and udder skin are thoroughly dry. Teat disinfectant products (eg, powder teat dips and other cold weather formulations) specifically designed for extremely cold weather are relatively successful at preventing frostbite after dipping. When liquid dips are used during periods of extremely low ambient temperatures, the teats should be dried before the cows exit the milking facility.
Moist, foul-smelling, necrotic lesions may develop in areas of tightly adjacent skin of some animals (such as the udder cleft). In heifers, the lateral aspect of the udder and medial aspect of the thigh are often involved. In this area, the udder is pressed tightly against the leg, resulting in chafing, dermatitis, and necrosis. Udder edema is a risk factor for development of this condition and must be treated concurrently. The necrotic skin should be cleaned daily with an antiseptic solution and thoroughly dried. Mild astringents should be applied. A similar condition, which may be associated with infestation by Sarcoptes mites, has been seen at the anterior portion of the udder between the two forequarters. Older cows have been reported to be at greater risk than heifers. The swollen, necrotic area may be treated topically with an approved miticide; however, appropriate milk withholding periods must be observed.