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18 Intradermal Testing (IDT) in Horses: The Australian Perspective Applications of IDT in Australia ACVSC Proceedings Dermatology Chapter Science Week 2005 Tina Baxter Intradermal testing (IDT) is probably an underutilized diagnostic tool in Australia. The incidence of atopy in Australian horses has not been documented. ‘Skin disease’ or ‘itch’ is a common presentation - approximately 20% of horse owners surveyed recently in Queensland reported their horses had a ‘skin problem’ (28) - and the majority of these had clinical presentations that were consistent with insect bite hypersensitivity. As the exact trigger of the skin disease was not identified in these cases, there may be a poor clinical distinction between insect related hypersensitivity and atopic dermatitis. More importantly, intradermal testing has applications in diseases other than atopic dermatitis, both here and overseas, and the following notes are equally relevant in performing the test for horses with insect bite hypersensitivity (including Queensland itch), recurrent urticaria, head shaking, chronic obstructive pulmonary disease and other airway diseases (reactive airway disease) where an allergic basis is suspected (7,12, 14, 16, 25). While Type I hypersensitivity is not the only contributing factor in these diseases, information gained from intradermal testing in these cases can only be of benefit. In a survey of aged horses, an estimate of 22% of horses had respiratory disease and the majority of these are thought to have an allergic pathogenesis (28). Possible reasons for the relative paucity of equine cases undergoing intradermal allergy testing include: The test requires time, skill and experience to perform, such that it is usually performed only by specialists in dermatology Much of the information and experience in IDT available to specialists in dermatology is based on small animals. Clinic facilities and personal preference of the dermatologist may preclude the handling of horses The allergens used in the test have a limited shelf life, so regular tests need to be performed to make the purchase of the allergens worthwhile and ensure the cost of the test to the individual owner remains reasonable Referral requires effort on the owners part to travel (in some cases significant distances from country regions of Australia) to the nearest major centre Costs and time to the owner: the average cost to the owner for IDT and consultation are around$500 to $650; costs of travel and time are additional
Comparatively simple, cheap and effective treatments are offered by the general veterinarian. Glucocorticoids, environmental management (such as stabling, rugging, topical insecticides), antibiotics and antihistamines are often prescribed, with many patients achieving acceptable control of their clinical signs with this management. Additional treatment options made available by results of IDT may be perceived to be more complex and expensive; allergen specific immunotherapy (ASIT) is an onerous task for many owners despite it’s benefits; and avoidance of allergens is usually impractical or impossible. Lack of awareness by horse owners that allergy testing is available and offers a beneficial alternative or adjunct to other standard treatments Often cases are referred as a last resort and poorer results are attained than had the case been referred early in the course of disease Education of both horse owners and veterinarians of the availability of IDT, and its means to improved management of many affected patients, is essential to improve the utilization of intradermal allergy testing as a diagnostic tool. Availablility of IDT in Australia There are only four centres in Australia at which equine intradermal testing is performed in Australia: Sydney Melbourne Perth Brisbane Following are the summarized details of the testing procedure, which for the most part, are similar across the different centres. Allergen Purchase For all four centres, allergen extracts are purchased through Dermcare Vet (Pty Ltd) who import the extracts from Greer Laboratories (Lenoir NC, USA). Allergen Selection Each centre has selected a range of allergens based on regional knowledge of relevant plants and insects, but is somewhat limited by the allergens available from the manufacturer. Allergen selection can be refined through various sources of information: Physicians in human allergy (and allergen testing panels from the same geographical region) National pollen charts; available from government agricultural organizations Local agronomists and botanists Entemologists may assist in insect species selection ACVSC Proceedings Dermatology Chapter Science Week 2005 19
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Page 33 and 34: TABLE 2 Additional allergens used i
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Page 41 and 42: Introduction Diagnostic Approach to
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Page 45 and 46: References Evans AG, Paradis MR & O
Page 47 and 48: Introduction: Equine Chronic Urtica
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Page 59 and 60: Equine sarcoidosis Sonya Bettenay T
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Page 67 and 68: Introduction The equine sarcoid: an
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Clinical Presentation Small fibrous
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Assessment should be made on the fo
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(ix)Bone becomes devitalized if inc
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and mitomycin C have been used. All
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Owen LN & Barnett KC (1983) - Treat
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any anatomic location but commonly
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epidermis may be histologically nor
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References D.C. Knottenbelt, S. Edw
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indicated. Each sample for culture
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Proper dosage and proper duration a
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2. Affect on the horse and 3. Affec
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Affected horses usually scratch and
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• Cattle ear tags impregnated wit
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How I treat: equine pemphigus folia
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Treatment of pemphigus foliaceus in
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SCOTT, D.W., WALON, D.K., SLATER, M
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Diagnosis History of access of hors
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These vaccines are not manufactured
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References Alfaro AA & Mendoza L (1
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y a variety of fungal metabolites.
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Authors recommendations: 1. Both Im
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chorioptic mange by the author (Lit
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Clinical Disease The clinical resul
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treatment options have been used. P
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Notes ACVSC Proceedings Dermatology
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