Skin diseases
A.Lecture Asaad Chasib Alatabi
Collage of Vetrinary Medicine
Department of Clinic
Lecture No.1
Introduction
The skin is the largest organ of the body and, depending on the
species and age,may represent 12-24% of an animals body
weight.
Functions of Skin
Including serving as an enclosing barrier and providing environmental
protection,regulating temperature, producing pigment and vitamin D, sensory
perception,to maintain a normal fluid electrolyte balance within animal , etc.
Anatomically, the skin consists of the following structures: epidermis,
basement membrane zone, dermis, appendageal system, and
subcutaneous muscles and fat.
The major effect of skin diseases in animals are esthetic and economic.
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Classification Skin Diseases
Diseases of the Epidermis and Dermis.such as Dermatitis
Piteriasis,Urtecaria,and Photosensitization.
Diseases of the Hair and Wool such as Alopecia and Seborrhia.
Diseases of the subcutis such as Anasarca and Angioedema.
Granulomatous Lesions and Congenital Defects.
Diagnosis of Skin Diseases
Physical Examination
Examination requires very close inspection of the entire hair,coat and skin
under strong lighting; flashlights may be necessary to examine the skin of
large animals.It is important to examine the ventrum of the animal, where
many primary lesions and cutaneous parasites are found.
Gross lesions can be described as focal, multifocal, or diffuse in distribution,
followed by a description of the affected region (eg, mucocutaneous, truncal).
On closer inspection.
lesions may be further described as primary or secondary.
A- Primary lesions. Include
1. Macules or patches (nonelevated areas of discoloration).
2. Papules or plaques (elevated lesions,the latter coalescing)
3. Pustules, vesicles or bullae (fluid-filled lesions).
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4. Wheals (flat-topped, steep-walled, solid elevations of the skin arising
from histamine release)
5. Nodules or tumors (large solid elevations of the skin).
B- Secondary lesions. Include
1. Erosions or ulcers (loss of the epidermis).
2. Scars, excoriation (areas of self-trauma).
3. Fissures,lichenification (increased thickening and hyperpigmentation of
the skin),and other lesions such as Dandruff,Ulcer, and Chap.
Some lesions may be either primary or secondary, depending on etiology
of the disease. These include alopecia, scales, crusts, follicular casts
(plugging of hair follicles with visible keratin),and pigmentary changes.
Laboratory Examination
1-Skin Scrapings: There are two types of skin scrapings, superficial and
deep.
2-Combing of the Hair Coat: This technique is useful for collecting large
amounts of skin debris and for trapping cutaneous parasites and some mites
combings are particularly useful for finding fleas, ticks, lice,
.3-Examination of Hairs: Microscopical examination of hair shafts can be
used to look for evidence of self-trauma, dermatophyte infections dysplastic
hairs.
4-Cytology: Cutaneous and auricular cytology is helpful in identifying
bacterial,fungal, and possibly neoplastic skin diseases.
5-Fungal Cultures: Dermatophyte infections are best identified with a fungal
culture on either dermatophyte test medium or on plain Sabouraud s agar.
6-Bacterial Cultures: Intact pustules can be cultured by rupturing the pustule
with a sterile needle and swabbing the lesion with a sterile culture swab.
7-Biopsy: Skin biopsies are indicated in any case that appears severe,
unusual, or does not respond to appropriate therapy.
Principles of Treatment
1) Good grooming practices.
.2) bathing animals.
3)Local ointment ,gel,and sprays.
4) Exudative lesions, eg, areas of pyotraumatic dermatitis are kept clean and
covered with an antibiotic ointment or gel .
5) The animal should be monitored closely for possible development of
irritant or allergic contact dermatitis from topical agents.
6) Owners should be given careful how to administer the therapy.
7)Shampoo Therapy: Shampoos are the most commonly used topical
treatments.There are three broad classes of shampoos: cleansing,
antiparasitic, and medicated
products. Medicated shampoos include antimicrobial products contain
chlorhexidine or benzoyl peroxide, shorten the course of infection.
Antiseborrheic shampoos contain some combination of tar,sulfur,and
Salicylic acid ingredients that are keratoplastic and keratolytic. Tar is
recommended for oily seborrhea, and sulfur and salicylic acid are
recommended for scaly seborrhea.Tar products are contraindicated in cats.
The animal should be washed in a cleansing shampoo before the medicated
shampoo.
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Dermatitis
Inflammation of the skin can be produced by numerous agents, including
external irritants, burns, allergens, trauma, and infection (bacterial, viral,
parasitic, or fungal).It can be associated with concurrent internal or systemic
disease, and hereditary factors also may be involved.
Clinical signs
The most common sign is scratching, followed by skin lesions that progress
from edema and erythema to papules, vesicles, oozing, and crusting or
scaling. Secondary infection may occur. As dermatitis becomes chronic, the
erythema decreases and there are fewer papules, but the lesions are drier
and the skin may develop fissures. Findings may vary considerably with the
species affected and the cause.
Diagnosis
1) history should be taken, noting the progression,presence of pruritus,
seasonality, the environment, food, exposure to and involvement of other
animals or persons, and any prior treatment.
2 - Physical examination should define the areas affected: generalized,
trunk, face, mucous membranes, etc.
3- skin scrapings for ectoparasites, skin culture for bacteria and fungi, skin
biopsy, endocrine evaluation, hypoallergenic diet, or intradermal skin testing,
should be performed when indicated.
Treatment
1- Topical and Systemic palliative therapy may be used. The hair should be
clipped from the affected and surrounding areas.
2- Acute moist dermatitis may be treated with astringent soaks (eg, Burow s
solution) or a minimally occlusive corticosteroid lotion or cream.
3- Chronic dry dermatitis is helped by application of a corticosteroid oint.
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To remove scales or crusts, a sulfur and salicylic acid.
systemic therapy , anti-inflammatory doses of corticosteroids,and
short-acting, oral drug should be used, eg, prednisone or prednisolone
initially at 1 mg/kg, PO, s.i.d., and gradually reduced to the lowest
possible every-other-day
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