Integumentary disorders

Chapter 3 Integumentary disorders




Introduction


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, 13.2213.24). 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).




Photosensitization (photosensitive dermatitis)




Clinical features


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 (13.2213.24). 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.










Differential diagnosis


BEPP (1.35), foot-and-mouth disease (12.212.8), 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.




Brown coat color


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.






Mange







Lice (pediculosis)



Clinical features


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.




Jul 8, 2016 | Posted by in SUGERY, ORTHOPEDICS & ANESTHESIA | Comments Off on Integumentary disorders
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