Chapter 3 Integumentary disorders
The skin is the largest organ of the body and performs a wide range of functions. It is mechanically protective against physical injury and provides a barrier against infections, many of which only become established when surface integrity has been compromised by physical or environmental trauma. Sense receptors detect touch and pain. Vitamin D is synthesized under the influence of ultraviolet light. Skin has a primary function in heat control, insulating against heat and cold, and through sweating, it acts as a thermoregulator. The depth and thickness of hair coat is the main factor affecting insulation.
The major breeds of cattle in Europe and North America are derived from Bos taurus and have a limited ability to sweat. Cattle derived from Bos indicus (Brahman, USA; Africander, Africa), such as the Santa Gertrudis, can sweat copiously for long periods, although there are considerable differences in sweat production from different regions of the body surface.
Visual appraisal of the skin is easily carried out and a wide range of disorders is recognized. Anaphylactic reactions can produce urticaria. Photosensitization may result from a range of intoxications including St. John’s Wort, Lantana, and facial eczema (see also Chapter 13, 13.13, 13.22–13.24). Parasitic (lice and mange), fungal (ringworm), bacterial infections (skin tuberculosis), and fly infestations (myiasis and warbles) all produce skin changes which are discussed in this chapter. The final section deals with physical conditions such as hematomas, abscesses, frostbite, other traumatic incidents, and neoplasia.
Many skin changes which are secondary to other diseases are described in the relevant chapters, for example, gangrene secondary to mastitis (see 11.8) or ergot poisoning (see 7.159), or subcutaneous swellings associated with urolithiasis (see 10.7) or umbilical (navel) conditions (2.9).
urticaria is sudden in onset. Cases are sporadic. The wheals do not itch. The Friesian cow (3.1) has raised plaques of edema (wheals) over the face and shoulders. The eyelids and muzzle are swollen. Although looking depressed, she was eating well and, like many such mild cases, recovered within 36 hours. The Simmental cow (3.2) was much more advanced, pyrexic, and in considerable pain. The head, grossly enlarged due to subcutaneous edema, was often rested on the ground. The skin of the muzzle was hyperemic. Localized areas sloughed a few weeks later. Some cases are allegedly due to snake bites or bee stings, but remain unproven.
photosensitization has a worldwide occurrence. Photoreactive agents accumulating under the skin convert ultraviolet light into thermal energy, leading to inflammatory changes that initially produce skin swelling, and, later, a possible slough. Only white or lightly pigmented skin is affected, since black skin prevents absorption of sunlight. The initial photoreactive agent may have been ingested (primary photosensitization), or may be produced as a result of liver damage (secondary or hepatogenous photosensitization). In cattle the principal secondary photoreactive agents are porphyrins and phylloerythrins, the latter being a normal end product of chlorophyll that is not metabolized further. Liver damage may result from ingestion of a wide range of drugs, plants, or chemicals.
in the early stages, affected animals show marked discomfort and pyrexia, with erythema and encrustation around the margins of the nostrils (3.3) and erythema of the teats (3.4), as in this Simmental cow. The teats are very painful and may later blister and slough (3.5), making milking almost impossible. The thickness of the skin slough, in this case only moderate, depends on the degree of initial damage. The primary febrile phase, edema, and thickening of the white skin had passed unnoticed in the heifer in 3.6, and she was presented with sloughing of dry, hard areas of white skin and with a new epidermis forming beneath. Seven weeks later (3.7) the new skin was well developed. Hair regrowth was possible owing to the preservation of hair follicles deeper in the epidermis. Areas of granulation tissue may retard healing (3.8), especially over bony prominences such as the pelvis. A dry dermatitis persisted in this cow for a further 2 years. The condition also occurs in Lantana poisoning (13.13) and facial eczema (13.22–13.24). Serum biochemistry or hepatic biopsy may aid confirmation of liver damage. A more advanced case, involving both udder and teats, is shown in (3.9). The associated pain plus thickening of the teat wall (which prevented the teats filling with milk) made this cow impossible to milk.
BEPP (1.35), foot-and-mouth disease (12.2–12.8), bluetongue (12.17), bovine herpes mammillitis (11.18), vesicular stomatitis (11.26, 11.27). The clinical presentation of early cases, where skin edema may be difficult to detect, strongly resembles colic.
during active photosensitization, cattle should be kept in the shade or preferably housed. Parenteral corticosteroids and NSAIDs may be helpful in early stages to reduce the extent of skin slough. B vitamins may help in cases with hepatic damage. Secondary skin infection and fly strike should be controlled. Skin lesions heal well despite extensive necrosis, leaving residual scarring and wrinkling.
Copper deficiency affects several systems (see 7.167–7.172), but classically causes loss of coat color. However, copper deficiency is not the only cause of brown coat color. Animals turned out to spring grazing may retain their winter coat (3.10), particularly younger animals in poorer body condition and first-lactation heifers. Although grazing the same pasture, the older animal at the rear is not affected.
Cattle are affected by four genera of mange mites, i.e., Sarcoptes, Chorioptes, Psoroptes, and Demodex, six species of lice, skin helminths (Stephanofilaria and Parafilaria), myiasis (screw-worm), and various fly infestations. In temperate climates parasitic skin infestations are more commonly encountered in housed cattle in winter. Many of the conditions cannot be differentiated on clinical examination alone and laboratory tests are necessary. Often several conditions coexist, e.g., mange, ringworm, and lice commonly occur simultaneously especially on cattle in poorer condition. The appearance and location of mange lesions are generally characteristic for the particular mite, although specific diagnosis depends on microscopic examination of the mouthparts.
Caused by Sarcoptes scabiei var. bovis, lesions are typically seen over the head, neck and hindquarters (3.11). Note the hair loss and severe thickening of the skin in 3.12. The white areas show secondary damage due to rubbing. In severe cases there may be almost total hair loss. The close-up view (3.13) shows the dry, scaly appearance of the thickened skin.
Chorioptic mange is the most common type of mange in cattle. The fold of skin beside the tail is the characteristic site for infestation by Chorioptes bovis (3.14). Lesions comprise a thick encrustation overlying an area of moist serous exudate. They are intensely irritant. In untreated cases the dry encrustation spreads down the perineum and over the posterior udder. In advanced cases (3.15) red, pustular lesions may be seen. Less commonly infection is seen in the neck and shoulder region (3.16).
Note the skin thickening and hair loss in the cow (3.17), extending from the vulva to the udder. The condition may start at the withers and spread over the whole body. Pruritus is often marked. Psoroptic mange (Psoroptes ovis) is notifiable in North America, where eradication programs have been in progress for many years. In recent years psoroptic mange has also become more common in South Wales and elsewhere in Europe, especially Belgium.
Small papules are seen on the white skin of this cow (3.18), from which a thick, white, waxy material containing large numbers of mites can be expressed. Another case (3.19) shows papules over the skin of the shoulder. Some nodules become secondarily infected with Staphylococci. The condition is generally mild, with a spontaneous recovery. Extensive hair loss is rare. Similar lesions are seen with Dermatophilus (3.38, 3.42).
as mite eggs take 2–3 weeks to hatch, and as mites can persist in the environment for around 2 weeks, two pour-on organophosphorus treatments, or two subcutaneous injections of ivermectin, 2–3 weeks apart, are needed. Alternative drugs are single doses of doramectin, or eprinomectin, both of which have greater persistence.
Psoroptic mange control is problematic. All affected and contact animals should be treated with injectable macrocyclic lactones or licenced pour-on products. But unlicenced products with greater efficacy in the UK are permethrin pour-on or Amitraz, prescribed by a veterinarian, and have potential milk and meat withdrawal disadvantages.
sucking lice (e.g., Haematopinus eurysternus and Linognathus vituli and, in North America, Solenopotes capillatus) are slower moving than biting lice (Damalinia [Bovicola] bovis). In addition to pruritus (the only lesion due to biting lice), sucking lice may produce severe anemia, loss of condition, and even death. Pediculosis is most prevalent in the winter months. Parting the hair along the back may reveal small, brown, motile lice just visible to the naked eye. They are more easily seen on white skin and hair, or on the hairless skin of the groin (3.20). Note the variation in their size.
Clinically, infestations are manifested by rubbing, biting, scratching, and thickening of the skin. In 3.21 the calf’s tongue is protruding and its head is held on one side, a stance typical of pruritus. In early cases the hair develops vertical lines on the neck. Small, hairless areas with white scurf may arise from biting. In more advanced cases the skin is thickened round the face and the vertical hair lines on the neck are thrown into thick folds, as in this adult Ayrshire cow (3.22). A further characteristic sign is the presence of clumps of hair (3.23) where affected cattle have been biting their pruritic skin, as opposed to licking and grooming it.
Younger calves especially may be stunted and anemic, and become much more susceptible to other diseases such as pneumonia, especially with sucking lice infestations. Ringworm often occurs in association with lice: early lesions are seen on the shoulder in 3.21. Pale beige-colored oval lice eggs (“nits”), glued onto the hair shafts, can often be seen with the naked eye, particularly on the ear (3.24 near the tag) and over the shoulders. In older animals the coat may become matted with lice eggs.
lice are most common in conditions of high stocking density, high humidity, a dusty environment, and in colder weather, when the coat becomes thicker. Eggs hatch over a period of 2–3 weeks, and adult lice can persist for around 2 weeks in the environment, so prolonged or repeated treatments are often necessary. Organochlorine compounds, e.g., gamma benzene hexachloride (BHC), are very effective but their use is now prohibited in most countries. Two organophosphorus treatments, 2 weeks apart, can be very effective, e.g., phosmet or coumaphos as a pour-on or as dips, but again their use is restricted in many countries. Permethrin synergized with piperonyl butoxide and tetrachlorvinophos can be used a spray or pour-on. Single pour-on applications of doramectin or eprinectin are also very effective against sucking lice. Badly infested cattle may benefit from multivitamins.
ringworm is a fungal infection of the superficial, dead, keratinized tissues of the hair and skin. Infection will often track into the hair follicles leading to a temporary alopecia. Trichophyton verrucosum is the most common cause in cattle, although occasionally Microsporum species may be involved. Ringworm is an important zoonosis.