5

Skin Diseases

(1) Pityriasis = Dandruff
It is non-infectious condition characterized by the presence of bran-like scales on the skin surface.
Etiology:
Hypovitaminosis A and B especially riboflavin and nicotinic acid mainly in pigs.
Nutritional deficiency acids as linolenic acid.
Poisoning by iodine ,which causing fatty acid deficiency.
Lice, flea and mange infestations.
May be with ringworm.

Pathogenesis:

The scales are keratinized epithelial cells and these are sometimes softened and become greasy due to exudation of sebum or serum. Avitaminosis A results in overproduction of keratinized epidermis. Excessive desquamation due to parasitic infestation is another way of pathogenesis and developing scales.

Diagnosis:

Primary Pityriasis depends upon the examination of skin scrapings. Differentiation from hyper-and parakeratosis. Skin scrapings to eliminate parasites and Fungi.

Treatment:

Correction of primary agents.
Using of balanced ration emollient ointment and alcoholic lotion.
Salicylic acid incorporated in ointment and lotions.

(2) Hyperkeratosis

It is the accumulation of excessive keratinized epithelial cells on the surface of the skin Resulting in thickening of the skin with or without hair loss .

Etiology

Localized at pressure points as elbow when the animal lays habitually on hard surface (Mechanical).
Chronic poisoning with arsenic compounds.
Poisoning with highly chlorinated naphthalene compound used in industry as in wool preservation.
Inherited as congenital ichthyosis = fish � scale disease of cattle . ( Alopecia with plates of horny layer allover the skin; this occurs in newly born animals specially calves) .
Pathogenesis
Local compression leads to accumulation of keratinized epithelial cells.
Excessive keratinization of epithelial cells and intercellular bridges and hypertrophy of stratum corneum.
In cases of poisoning with chlorinated naphthalene, it causes deficiency of the granular layer of epidermis and causing atrophy of epithelial cells .
Clinical finding
The skin becomes thicker than normal and usually hairless and corrugated .
Skin becomes dry and fissures develop in grid � like fashion .
Secondary infection through the fissures when the skin is wet .
Diagnosis
Differentiation from parakeratosis.
Skin scrapings to eliminate ectoparasites and fungal infection.
Histological examination of skin biopsy to detect the thickened stratum corneum.
Treatment
Correction of the primary cause.
Us of balanced ration, emollient ointment and alcoholic lotion.
Salicylic acid incorporated in ointment and lotions.
Using of vitamin A as 6000 I.U


(3) Parakeratosis
It is a condition of the skin in which keratinization of epithelial cells is incomplete.

Etiology

Non , specific chronic inflammation of cellular epithelium which leads to faulty keratinization of horny cells.
Dietary deficiency of saturated fatty acids. Additional dietary zinc deficiency along with copper alleviates the condition, which is effectively prevented by supplements of soybean oil or some other suitable source of linoleic acid.
Inherited dermatosis vegitans in pigs.
Pathogenesis
Edema of prickle cell layer, with dilatation of intercellular lymphatic vessels and leucocytic infiltration lead to Imperfect keratinization at granular epithelium. Layer of epidermis produces sticky and soft horn cells, which retain their nuclei and they tend to stick from large masses and either still fixed to underlying tissues or may fall off as forge scales.

Clinical Findings

Lesions may be diffuse and extensive but often confined at flexor aspects of joints.
Reddening, thickening and gray coloration of skin.
Cracks and fissures also develop and removal of scales leave raw and red surface.
Diagnosis
Histologically: imperfect keratinization is evident.
When the scales are removed it leaves raw and red area so differentiation from hyperkeratosis will be easy.
Treatment
The deficiency in ration must be corrected buy addition of zinc continuously using zinc sulphate or zinc oxide.
Removal of scales by using keratolytic ointment as that of salicylic acid ointment or by warm soapy water.
Local application of astringents as white lotion paste.
(4) Urticaria (Nettle Rash)


Urticaria is an allergic condition characterized by the appearance of wheals on the skin surface.
Etiology
It may be a primary lesion resulting from the direct effect of pathogen on the skin , or may be secondary as part of a syndrome .
(A) Primary Urticaria due to:
Insect bites.
Ingestion of unusual food ,mainly protein and sudden changes of diet is a predisposing factor.
Drug administration (e.g. penicillin).
Death of warble fly larvae in tissues.
(B) Secondary Urticaria due to:
Alimentary tract disturbances in horse.
Respiratory tract infection in horse.
Along the course of some disease.

Pathogenesis

Urticaria represents a type of immediate hypersensitivity on which the binding of antibody with antigen results in release of Histamine.
Primary dilatation of capillaries causes erythema of skin .
Exudation from damaged capillaries leads to local edema of epidermis with swelling and pallor due to compression of capillaries.
The lesions remain red at the edges and only the epidermis is involved.

Clinical Findings

Lesion develop rapidly, large in numbers, ranges from 0.5 - 5 cm diameter with flat-topped steep-sided plaques, and tense to touch.
No exudation or weeping occurs; No itching except with insect bite.
Plaques mainly found at back, flank, neck and legs.
It may subside in 24 hours or last up to 5 days.


Clinical Pathology
There is an increase of histamine level and local increase of eosinophils count.

Diagnosis

Urticaria must be differentiated from angioneurotic edema; In cases of edema, the subcutaneous tissues are involved.

Treatment

Antihistaminic with parentral administration of adrenaline.
A mild purgative and corticosteroids may be used.
Local astringent as white lotion, calamine lotion or dilute solution of sodium bicarbonate.
In large animals, parentral administration of calcium salts.
Changing the diet is helpful in cases of food allergy.