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98 Cards in this Set
- Front
- Back
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What is atopy?
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A type 1 hypersensitivity to environmental allergens (dusts, pollens, moulds) mediated by IgE, causing mast cells to release granules
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What do the granules that mast cells release in atopy contain?
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Substances that cause erythema, vascular leaking and pruritus
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How do you diagnose atopy?
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Exclusion of other ddx (culicoides hypersensitivity); skin biopsy, intradermal testing, serum ELISA
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Main C/S of atopy?
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Extreme pruritus
Alopecia Erythema Erticaria Self-inflicted lesions |
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Where do atopic lesions occur?
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Face
Distal limbs Trunk |
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Tx of atopy?
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Systemic corticosteroids
Antihistamines AB for secondary infection EFA in food Hypersensitisation shots? |
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What do aural papillomas look like?
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Small papules on the inner surface of the pinnae that coalesce into white hyperkeratotic plaques
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Where else do aural plaques occur?
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Genitals and mammary glands
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Is tx required for aural plaques?
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No, even though spontaneous regression does not seem to occur
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What are the main types of bacteria that cause most cellulitis?
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Staphs
Corynebacterium pseudotuberculosis |
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What are the characteristics of staph cellulitis?
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A severe, deep, suppurative process in which a poorly defined area of infection dissects through tissue planes
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Main staph spp involved in cellulitis?
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aureus and intermedius
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C/S of cellulitis?
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Usually distal limbs or pectoral region; acute painful swelling and lameness and systemic signs like pyrexia and increased HR (bacteraemia); the overlying skin becomes devitalised and sloughs
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Characteristics of corynebacterium cellulitis?
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Solitary or multiple abscess or nodules with many draining tracts that progress to diffuse cellulitis; can rupture viscid, creamy pus
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Tx of cellulitis?
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AB for a minimum of a month
NSAIDs |
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What mite causes leg mange?
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Chorioptes equi
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What part of the leg is primarily affected by chorioptes?
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Distal limbs (pastern) and ventral abdomen of heavily feathered horses
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C/S of leg mange?
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Papules, erythema, alopecia from self-trauma; exudation from secondary infections; horses stamp and bite limbs
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Tx of chorioptes?
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Remove hair and scabs and give fipronil once weekly for a month (even to in-contacts); shampoo for pruritus?
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What bacteria causes mud fever and rain scald?
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Dermatophilus congolensis
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What are the 3 main types of cysts that horses get?
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Dentigerous
Dermoid Epidermoid (atheroma) |
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What is a dentigerous cyst?
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Swelling in the temporal region arising from tooth germ tissue; drains through skin or near the ear
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What is a dermoid cyst?
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Cutaneous cysts along dorsal midline; contain cheesy material or hairs
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What is a epidermoid cyst?
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A cyst in the epidermis that is most common in the false nostril where it is called a "atheroma"
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What is habronemiasis known as to lay people?
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Summer sore
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What helminths cause habronemiasis? (3)
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Habronema muscae
Habronema majus Drachia megastoma |
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Pathogenesis of Habronemiasis?
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The helminths are transported by house and stable flies; the adults usually reside in the tum and dont cause problems; cutaneous lesions occur when larvae are depositedon damaged skin or areas of natural moisture
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What are the characteristic lesions in cutaneous habronemiasis?
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Ulcerating, granulating nodules or ulcers near the medial canthus, male genitals, 3rd eyelid and distal extremeties
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2 main types of habronemiasis?
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Ophthalmic
Cutaneous |
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Interesting relationship with cancer and habronemiasis?
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Lesions in habro look like neoplasia and habro can actually infect SCC
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Characteristics of ophthalmic habronemiasis?
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Presence of yellow granules in conjunctivae and nasolacrimal duct
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Diagnosis of habronemiasis?
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Impression smears and washes; biopsy
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Tx of habronemiasis?
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Oral/topical ivermectin
Steroids for hypersensitivity Surgical removal Control of flies |
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What is leucoderma (vitiligo)
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Loss of pigment in skin causing depigmented spots; around eye and perineum
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What is lymphangitis?
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Inflammation of cutaneous lymphatics secondary to a bacterial infection obtained via a small abrasion
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C/S of lymphangitis?
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Marked swelling of limb (hind more common than fore) by 2-3 times normal and serum exudation
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Tx of lymphangitis
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AB
NSAIDs/steroids Diuretics Leg wraps |
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Where are melanin pigmet dopts (hamartomas) common?
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Linings of GP
Mucosae |
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What type of horse is prone to melanomas and where do they like to occur?
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Grey hores
Perineum, sheath, parotid region, GP, eyelid, lips |
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Tx of melanoma/sarcoma?
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Surgical excision
Intralesional cisplatin |
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What conditions must be present for dermatophilus to manifest itself?
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Carrier animal
Moisture (allows release of zoospores, the infective stage) Skin abrasions |
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Transmission of dermatophilus?
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Biting and non-biting flies, ticks and fomites
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C/S of mud fever (dermatophilus)
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Exudation, scabs and matting of hair of distal (often white) limbs as well as dorsum and muzzle
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Tx of mud fever?
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AB (penicillin G BID or TMPS BID for 7-10 days) because derm is G (+); chlorhexidine to remove scabs and exudate
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What spp causes onchocercal dermatitis?
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Onchocerca cervicalis microfilaria
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How is O. cervicalis transmitted?
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Culicoides sp and other biting insects
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Pathogenesis of onchocercal dermatitis?
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Adults usu found coiled in funicular part of nuchal ligament where they produce calcified nodules' microfilaria migrate through CT to superficial dermis, lower eyelid and lateral limbus of eye
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Type of hypersensitivity rxn involved in onchocercal dermatitis?
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Type 1 and 3 due to antigens released by dying microfilariae
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C/S of onchocercal dermatitis?
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Alopecia and scaling of hear, neck, withers and chest; ocular lesions include uveitis, conjunctivitis, keratitis and a depig of the lateral limbus; can be very pruritic
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What time of year does onchocercal dermatitis usu occur?
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Summer
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Tx of onchocercal dermatitis?
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Ivermectin
Moxidectin Improve within 2-3 weeks |
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Where do viral papillmas usually occur?
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White-grey papules on muzzle, lips, eyelid, external genitalia and limbs
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What age of horse is affected by viral papillomas?
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Under 3 years old
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Main lice that affect horses?
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Damalina equi (biting)
Haematopinus asini (sucking) |
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C/S of pediculosis?
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Pruritus
Scaling Alopecia Self-trauma |
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Tx of pediculosis?
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Shampoos or sprays containing pyrethrins or pyrethroids like cypermethrin - two applications at 14 day intervals are usually sufficient
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What causes pemphigus foliaceus?
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Type 2 hypersensitivity due to autoantibodies directed against the transmembrane protein of epidermal cells resulting in the release or activation of 1 or more proteolytic enzymes; these destroy the attachments bt adjoining epi cells = acantholysis and the formation of intraepidermal vesicles
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What is the initial lesion in PF?
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Pustule
Rupture quickly resulting in collarettes, scale and crust |
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C/S of PF?
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Vesicles, pustules, scaling and crusting that begins around the face and limbs; spreads everywhere after days/weeks. Can get systemic signs of anorexia, ventral oedema, pyrexia and weight loss
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Diag of PF?
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Biopsy
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What is PF?
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Autoimmune disease characterised by an exfoliative dermatitis
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Tx of PF?
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Immunosuppressive doses of corticosteroids (pred or dex); can also use azathioprine as a steroid-sparing drug but the side effect is thrombocytopaenia
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What areas does rain scald affect?
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Back and quarters, giving paint-brush lesions
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What is dermatophytosis?
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Infection of keratinised tissues of skin (s. corneum layer of epidermis) causing weakened hair shafts and alopecia
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Main causes of ringworm?
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Trichophyton spp
Microsporum spp |
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Main 2 trichophyton spp?
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Equinum var equinum
Equinum var autotrophicum |
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Common areas for ringworm lesions?
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Face
Axillae/girth Trunk Limbs Can sometimes get coronary band disease |
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Diag of ringworm?
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Microscopy of a hair pluck/scrape
Woods lamp - only microsporum will fluoresce |
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Tx of ringworm?
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Not really necessary as lesions resolve spontaneously over weeks
Fungicides like enilconazole, natamycin; tx environment too (natamycin or virkon) |
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Which is more common - trichophyton or microsporum?
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Tricho
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Aetiological factors behind SCC?
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Smegma (penile/vulva forms)
UV light (skin and eye forms) |
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Tx of SCC?
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Surgical excision
Intralesional cisplatin Radiation (beta) |
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What is sweetitch?
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A hypersentivity response to salivary antigens of culicoides spp midges
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Main culicoides spp to cause sweetitch problems?
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C. variipennis
C. nubeculosus |
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Usual onset of sweetitch?
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Bt 2-4 years olf
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Main areas affected by sweetitch?
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Main, tail, saddle, rump, ventral midline
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C/S of sweetitch?
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Alopecia
Papules Erythema Pruritus |
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Tx of sweetitch?
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Corticosteroids
Immunotherapy Fly repellants Stabling at dusk/dawn Rugs Fans |
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When do trombiculids affect horses?
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Late summer and autumn
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C/S of trombiculosis?
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Crusts and papules on face, neck and extremeties
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What is urticaria characterised by?
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Transient focal swellings in the skin or mm called wheals which represent localised areas of dermal oedema which results from vasodilation and transudation of fluid from capillaries and small blood vessels - mediators are released from mast cells and blood basophils that produce wheals
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What causes urticaria?
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It is a complex immune-mediated/allergic condition; can arise from injections, ingested chemies or feed, inhaled pollens, moulds, etc. These cause a type 1 IgE reaction. Can also get physical urticaria - pressure urticaria (dermatographism), cold urticaria and exercise-induced
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C/S of urticaria?
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Wheals that pit under pressure
Variable pruritus Lesions on cervical and craniolateral thorax |
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What is the subcutaneous form of urticaria called?
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Angio-oedema; really identical but involved SC tissue and often the entire face/neck
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Tx of urticaria?
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Find intial cause
Corticosteroids |
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What is vasculitis?
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An inflammatory reaction involving the blood vessel walls; usually type 1 or 3 immune-mediated
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3 types of vasculitis?
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Cutaneous
Pastern leukocytoclastic Purpura haemorrhagica |
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C/S of cutaneous vasculitis?
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Purpura of head and extremeties; oedema, necrosis and ulceration...can get systemic signs
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Tx of cutaneous vasculitis?
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Corticos +/- AB
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Where does pastern leukocytoclastic vasculitis affect?
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Unpigmented medial and lateral pastern; multiple and well-demarcated lesions
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C/S of pastern vasculitis?
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Erythema and oozing initially, crusting and ulcers followed by oedema of limb
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What does biopsy of pastern vasculitis show?
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Leukocytoclastic vasculitis
Vessel wall necrosis Thrombosis involving the small vessels in the superficial dermis |
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Tx of pastern vasculitis?
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Clean exudates and scabs
Corticos (sys or topical) AB for secondary infection (TMPS) Sunblock |
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What is purpura haemorrhagica?
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Immune-mediated vasculitis assd with recovery of an URT infection (s. equi M protein antigen)
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Patho of purpura?
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Immune complexes deposit in the walls of peripheral blood vessels increasing vasc permeability and causes oedema of limbs
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C/S of purpura?
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Skin erosions and exudation marked; petechial haem on skin and mucosae; life-threatening pulmonary or cerebral oedema possible
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When does purpura occur?
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2-4 weeks after resp infection
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Tx of purpura?
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Sys corticos
AB |
