Diseases of Bovine Teats and Skin

Bovine herpesvirus (BHV) II and IV can cause an acute, ulcerative condition of teat and udder skin of dairy cows that is often referred to as bovine ulcerative mammillitis or simply herpes mammillitis. It may result in reduced milk production and increased susceptibility to bacterial mastitis. Infection may simply lead to seroconversion.

Bovine ulcerative mammillitis can occur sporadically or in seasonal outbreaks often associated with cold weather. The greatest incidence occurs in first-lactation cows; however, previously unexposed cows of any age are susceptible.

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 cover much of the teat wall and orifice. Teats are generally painful, and affected cows often resist milking, contributing to development of mastitis. Severe lesions may take several weeks to heal.

Diagnosis is based on clinical signs and confirmed by histologic evaluation or by virus isolation from early lesions.

Treatment is supportive because there is no effective definitive treatment for this virus. The use of iodophor-containing teat dips with added emollients may help to inactivate the virus. To prevent transmission of the agent to susceptible animals, it is important to isolate affected cows, to use separate milking equipment, to clean and dry teats with single-use towels, and for milking personnel to wear clean gloves.

Pseudocowpox is primarily a condition of teat skin caused by pseudocowpox virus (paravaccinia virus) of the genus Parapoxvirus in the family Poxviridae. The virion is enveloped and contains a double-stranded DNA genome.

Pseudocowpox is the most common and widespread pox viral infection of teats, although it is rare when good udder hygiene is applied. Outbreaks are usually acute with rapid transmission among the herd. Infections are recurring; immunity is low and rapidly lost. Pseudocowpox is zoonotic and may affect milking personnel, causing cutaneous lesions called milker’s nodules to form on their hands.

Lesions start as a small red papule surrounded by up to a 5-mm radius of erythema. They progress to a circular 7-mm-diameter lesion with a central vesicle before developing a characteristic horseshoe-shaped lesion or scab after 10–12 days. The lesions resolve after 3–5 weeks. While adult cows develop teat lesions, cattle < 2 years of age develop small erosive lesions on margins of the lips, muzzle, and buccal mucosa. Circular lesions in the mouth can raise suspicion for reportable vesicular diseases (eg, foot-and-mouth disease and vesicular stomatitis).

Teat disinfectants help heal lesions by promoting good skin condition and preventing secondary bacterial infections.

Cowpox is a skin disease caused by cowpox virus of the genus Orthopoxvirus in the family Poxviridae. The virion is enveloped and contains a double-stranded DNA genome. Cowpox virus is closely related to the vaccinia virus and in the same genus as variola virus (the cause of smallpox).

Cowpox has become rare but remains endemic in western Eurasia; disease is now most common in domestic cats, with wild rodents serving as an animal reservoir for the virus. Cowpox virus is zoonotic. The observation that milkmaids who previously had cowpox did not catch smallpox inspired the first smallpox vaccination in humans.

Lesions start as a papule, progress to a yellow pustule, and then develop a depressed center. Infection results in lifelong immunity.

Differential diagnosis of other vesicular lesions on teats should include vesicular stomatitis, which is geographically limited, and foot-and-mouth disease.

Papillomas or fibropapillomas on teats develop due to infection with several strains of bovine papillomaviruses (BPV). Bovine papillomaviruses have a circular double-stranded DNA genome and are nonenveloped.

Bovine papillomaviruses are very stable in the environment. Bovine warts are transmitted by direct and indirect contact, and bovine papillomavirus DNA has been identified in blood, milk, urine, and other biological fluids obtained from infected animals.

Bovine infectious papillomatosis manifests in two common forms. Pale, smooth, raised, benign nodules due to BPV5 develop frequently on teat skin. They may be extremely abundant on the teat skin of antepartum heifers. Some nodules may persist indefinitely without causing problems; however, most resolve spontaneously. Filamentous or frond-like lesions develop at the teat orifice or on the ventral teat barrel and interfere with milking, either directly by impeding milk flow or indirectly by affecting the teatcup liner closure.

Diagnosis is usually made presumptively based on examination of the lesions.

In many instances, treatment of warts is not necessary; however, frond-like lesions that interfere with milking may need excision. The use of autogenous vaccines and viricidal, especially low-pH teat dips may be recommended in herd outbreaks or for newly calved heifers.

Teat-end hyperkeratosis (raised smooth or rough rings at the teat ends) is common in lactating cows and is associated with the keratin dynamics of the streak canal. The occurrence is related to both genetics and milking systems. Hyperkeratosis is most common on tapered and point-shaped teats and is absent from flat-ended teats or those with an inverted orifice. The presence of a 2-mm, smooth, doughnut-shaped ring around the orifice is not abnormal and distinct from development of excessive keratin fronds that may extend to all of the ring and up to 5 mm in length. These are distinct from warts.

The extent of hyperkeratosis changes through lactation, being least at parturition, increasing until peak lactation, and then decreasing to the end of the lactation. This has been related to the type of milking system; however, hyperkeratosis occurs in beef cows and hand-milked cows too. Further, the proportion of cows affected in any herd varies from 0% to 80%, as does the extent of keratinization. Teat shape, determined by genetics, may be more important if a good milking system is being used.

Diagnosis is usually made by clinical examination. The extent of hyperkeratosis is often characterized by scoring teat ends after cluster removal as:

• no ring

• smooth ring

• hyperkeratosis affecting some but not all of the ring and extending to 2-mm fronds

• hyperkeratosis affecting all of the ring and extending to 2-mm fronds

• hyperkeratosis affecting all of the ring and the fronds extending in parts beyond 2 mm

The latter condition is rare, and the rougher scores are often aggregated.

When teats are severely affected, the ability to properly sanitize teat ends before and after milking may be compromised. This has been related to coliform mastitis.

Teats may be swollen immediately after machine milking. The teats are turgid and shiny due to distention of the skin. Nonpigmented teats may appear red or blue. This is due to impaired circulation and is transitory. It is mostly retention of fluid in the blood vessels and only slightly in the intercellular tissues; hence, not a true edema. The most common causes are too high a milking vacuum, poor to no pulsation, overmilking of more than two minutes, and milking with a tapered liner or large mouthpiece liner.  The last is further indicated by a distal collar of congestion where the liner mouthpiece fitted on the teat.

Teats with good skin condition are smooth. The skin may appear and feel rough due to environmental conditions and lack of skin conditioning from teat disinfection. Pigmented skin usually shows roughness more easily. This is most easily observed before milking, as milk is a limited emollient.

Chaps are cracks or fissures along the folds of the skin, usually lateral or slightly oblique. They are commonest on the cranial surfaces of fore teats and the caudal surfaces of hind teats. Teats can chap when teat skin becomes dehydrated or exposed to wet cold conditions. Main risk factors include absence of postmilking teat disinfection, use of harsh teat disinfectants, or too little suitable emollient in the teat disinfectant in harsh environmental conditions. A minimum of 5% glycerin is essential. Chaps are readily colonized by various mastitis-causing bacteria, principally Staphylococcus aureus, Streptococcus dysgalactiae, and occasionally Trueperella pyogenes. Prevention of chapping has been one of the most important advances in reducing the prevalence of mastitis in dairy farming.

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 <−17.8°C (< 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. Teats should be dry before the cows exit the milking facility.

Nonpigmented teats may be sunburned, usually only on the side exposed when the cow lies down. Sunburn is most likely in pastured cattle at high latitudes and in areas with high ultraviolet B exposure. Cows may lick the irritated skin, causing a sore that attracts flies and leads to a bacterial infection.

High-emollient teat disinfectants are recommended; some may contain a sunblock.

Blackspot is a common name for a necrotic area at the teat orifice that has a secondary infection, usually of Staphylococcus aureus. A primary lesion is most commonly due to poor milking conditions (eg, high vacuum or impaired pulsation). This is often obvious when several cows are affected. The damage to the sphincter is often extensive and milking difficult or impossible. 

Surgical intervention may be necessary. High-emollient teat disinfectants may be beneficial, although conversely, hypochlorite teat disinfectants promote healing by aiding removal of dead tissue.

Dermatitis of the teats or udder has a number of causes, including environmental or chemical irritants, photosensitization, sunburn, and infection.

Dermatitis may result on the whole lateral body in cows using cooling ponds or standing in contaminated waterways, often with a sharp upper line of demarcation (described as a tide mark). Exposure to chemical irritants may come from sources such as bedding or bedding additives (eg, excess lime or disinfectants or some abrasive bedding sands), chemicals used during milking, or urine. Some teat disinfectants, especially if incorrectly diluted, may cause dermatitis, and often the milker is affected, too. Chemical causes may create erythema, pain, and alopecia in the most sensitive cows.

Photosensitization occurs when a photodynamic agent causes the skin to become sensitive to sunlight or ultraviolet light. Primary photosensitization occurs when a chemical is ingested or absorbed by the skin. Secondary photosensitization occurs in response to accumulation of phytoporphyrin. Usually only white or lightly pigmented skin is affected, with a response similar to a burn. The teats are painful, milking is rarely possible, and affected animals seek shade or stand in water. Topical exposure to various plants also contributes. Irritation usually resolves after removal of the offending substance; however, gentle udder washes and use of high emollient products can hasten 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 with an antiseptic solution until the condition resolves.

Other conditions include sarcoptic mange and ringworm.

Moist, foul-smelling, necrotic lesions may develop in areas of tightly adjacent skin of some animals (eg, udder cleft and adjacent to a leg). 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, associated with infestation by Sarcoptes mites, occurs at the cranial portion of the udder between the two forequarters. Older cows are 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. Subcutaneous abscesses of the udder (not involving the milk-producing tissue) can develop between the skin and the supporting connective tissue of the udder. Diagnosis is by needle aspiration. Abscesses usually develop secondary to wounds, chronic mastitis, infected hematomas, or severe contusions. They should be incised and drained when chronic, if near the surface of the udder. The wound should be flushed daily with an antiseptic solution or water under pressure until healing is complete.