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congolensis is not easy to isolate, particularly from older, longstanding lesions. However, typical organisms may be seen in wet preparations made from crusts after rehydration and maceration on slides, prior to staining. Dermatophilosis is often a problem of a number of horses in a yard and may be endemic, with increased numbers of affected animals noted in the winter months. The spores are persistent in the environment and careful attention to management practices is an important part of control measures. Ideally an area should be set aside for topical treatment of affected animals and crusts carefully disposed of and the area disinfected. Systemic antibiotic therapy is usually effective in cases not responding to topical antibacterial agents, but should be continued beyond clinical cure. Dermatophytosis can be caused by a number of fungal organisms. Identification of the causal agent may be helpful in identifying the original source (other horses, cattle, cats, sylvatic species, geophilic). There is also a zoonotic risk to be considered. Scalp brushes provide a useful tool for sampling animals for culture, equivalent to the Mackenzie toothbrush technique employed in small animals. Management of this condition is covered later. Pastern folliculitis may be a primary pyoderma, but mixed growth of organisms is frequently obtained on swabs. Tissue samples obtained by biopsy may well be a better material for culture and provide a truer picture of the major pathogen involved. However, cytological examination often provides sufficient information to initiate antibacterial therapy. Management of bacterial folliculitis is the subject of a later presentation. Chorioptic mange is the major parasitic cause of skin lesions of the distal limb. The parasite exhibits a preference for heavy breeds of horse. An epidemiological study conducted by the author has shown that the presence of feathers is not a prerequisite, but the actual nature of the nutritional or other factors provided by such horses is unknown. Management of this condition is covered later. Harvest mite larvae (“chiggers”) can parasitise the lower limbs of horses grazed on pastures inhabited by the free-living adult mites or ridden through infested woods or trails. The larval stage requires a blood meal and any convenient mammal may be bitten. The larva is only attached for 48-72 hours, but in some horses lesions of pruritus, crusting, erythema and scaling may persist beyond detachment of the parasite, suggesting a hypersensitivity component to the lesions. Fipronil has been demonstrated to be effective in the management of trombiculidiasis in dogs, and would be appropriate for the condition in equine patients too, as an off-label use. Photosensitivity may affect the distal limbs of horses with white socks. The cause may be due to ingestion of primary photosensitising agents, such as hypericin in Hypericum spp. of plants (St John’s Wort). Photocontact dermatitis may occur. In the case of primary photocontact or systemic photosensitisation, one would expect several of a group of horses to be affected, although photoallergic reactions may occur, which would be limited to sensitised individuals. Often it is difficult to 56 ACVSC Proceedings Dermatology Chapter Science Week 2005
identify plants in a pasture that might be implicated. It has been observed that some pastures rich in clover may be associated with cases of photodermatitis in some seasons, possibly associated with high rainfall and lush growth, but the exact nature of the agent remains obscure. Secondary, hepatogenous, photosensitisation occurs when pre-existing liver damage results in failure to metabolise chlorophyll effectively and presence of photoactive phylloerythrin in the circulation. The commonest cause of chronic liver damage in such cases is poisoning resulting from ingestion of Seneccio spp (ragwort), but mycotoxins have also been implicated. The prognosis for cases with underlying liver pathology is poor, but cases of primary photodermatitis respond to removal from the source of photoactive agent and ultraviolet light exposure and appropriate symptomatic therapy of lesions. A condition characterised histologically by vasculitis, which appears to be photoactivated, has been described. The nature of the underlying aetiology remains to be elucidated, but such cases usually respond well to glucocorticoid therapy and protection from further ultraviolet light exposure. This entity may well underlie some of the cases of so-called “canon keratosis” described in the literature. It is clear that this syndrome is not due to urine splashing in intact stallions (“stud crud”) since it occurs in females too. As ever, there are some cases of crusting lesions of the distal limbs that defy attempts to make a definitive diagnosis and are termed idiopathic. Lesions of the coronary band present a distinct range of differential diagnoses. The use of various and sundry topical hoof products may be associated with irritant or allergic reactions of the coronary band. Dermatophytosis may be restricted to this region. Congenital dystrophies are described. Acquired lesions of the coronary band can be seen in pemphigus foliaceus, which in the older horse is not infrequently confined to the coronary bands. Lesions may also affect the ergots and chestnuts and the oral mucosa may be involved. The prognosis for complete cure of such cases is poor, but most cases appear to respond to immunosuppressive therapy with glucocorticoids and long-term remissions can be achieved, with return to useful work. Chronic selenosis due to ingestion of plants with high selenium content, or accidental misformulation of concentrate feeds results in a coronitis and abnormal hoof growth. Loss of mane and tail hair are other features, together with weight loss and unthriftiness. Prognosis is dependent upon the severity of lesions, with the hoof deformity and pain seen in some cases necessitating euthanasia. Coronary band lesions with a histological appearance similar to that seen in hepatocutaneous syndrome have been encountered in horses with severe liver pathology. The coronary band is frequently involved in the rare condition of exfoliative eosinophilic dermatitis and stomatitis/enteritis syndrome, which carries a grave prognosis. ACVSC Proceedings Dermatology Chapter Science Week 2005 57
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Australian College of Veterinary Sc
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Australian College of Veterinary Sc
Page 5 and 6: 3.00 Afternoon tea 3.30 How I treat
Page 7 and 8: Dr Jennifer A. Charles BVSc MVS Dip
Page 9 and 10: Scientists in Feline Medicine in 19
Page 11 and 12: IgE-bearing cells have been demonst
Page 13 and 14: years, median age 6.5 years, with a
Page 15 and 16: dusts, grain smuts, moulds, danders
Page 17 and 18: References: Evans AG, Paradis MR, &
Page 19 and 20: Comparatively simple, cheap and eff
Page 21 and 22: TABLE 1: CURRENT ALLERGENS SELECTED
Page 23 and 24: AmericanCockroach Cockroach mix
Page 25 and 26: Patient Preparation Drug Withdrawal
Page 27 and 28: Each injection site is visually exa
Page 29 and 30: References 1. Scott DW, Miller WH:
Page 31 and 32: Intradermal Testing (IDT) in Horses
Page 33 and 34: TABLE 2 Additional allergens used i
Page 35 and 36: Allergen Positive reactions Mosquit
Page 37 and 38: much higher and corresponded to the
Page 39 and 40: and this and other uncontrolled tri
Page 41 and 42: Introduction Diagnostic Approach to
Page 43 and 44: Wheals vary in size and shape and q
Page 45 and 46: References Evans AG, Paradis MR & O
Page 47 and 48: Introduction: Equine Chronic Urtica
Page 49 and 50: Acute treatment - Epinephrine 1:100
Page 51 and 52: anecdotal success with use of human
Page 53 and 54: an 80:20 mixture of evening primros
Page 55: Clinical approach to the horse with
Page 59 and 60: Equine sarcoidosis Sonya Bettenay T
Page 61 and 62: described as a possible feature of
Page 63 and 64: others 2001), isotretinoin(Waldinge
Page 65 and 66: 12. LeGall, F., Loeuillet, L., Dela
Page 67 and 68: Introduction The equine sarcoid: an
Page 69 and 70: Clinical Presentation Small fibrous
Page 71 and 72: Assessment should be made on the fo
Page 73 and 74: (ix)Bone becomes devitalized if inc
Page 75 and 76: and mitomycin C have been used. All
Page 77 and 78: Owen LN & Barnett KC (1983) - Treat
Page 79 and 80: any anatomic location but commonly
Page 81 and 82: epidermis may be histologically nor
Page 83 and 84: References D.C. Knottenbelt, S. Edw
Page 85 and 86: indicated. Each sample for culture
Page 87 and 88: Proper dosage and proper duration a
Page 89 and 90: 2. Affect on the horse and 3. Affec
Page 91 and 92: Affected horses usually scratch and
Page 93 and 94: • Cattle ear tags impregnated wit
Page 95 and 96: How I treat: equine pemphigus folia
Page 97 and 98: Treatment of pemphigus foliaceus in
Page 99 and 100: SCOTT, D.W., WALON, D.K., SLATER, M
Page 101 and 102: Diagnosis History of access of hors
Page 103 and 104: These vaccines are not manufactured
Page 105 and 106: 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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