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Flashcards in Equine Deck (174)
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159

Problem?  Transmission? Geographically? Treatment? Signs and symptoms? Who? Diagnosis?

* Onchocerca cervicalis- common filarial dermatitis

* Adults live in nuchal ligament-- microfilaria migrate through superficial dermis

* Infection transmitted between horses by Culicoids spp. (IH-- larvae develop to L3)

* Worldwide

* Treatment- ivermectin (also used for routein deworming)

* Can sometimes cause a hypersensitivity to dying microfilariae (treatment can temporarily exacerbate)

* Ocular and cutaneous lesions-- uveitis, conjunctivitis, keratitis, depigmentation, diffuse/patchy alopecia, erythema, scaling

* Older horses, non-seasonal

* Diagnosis: biopsy but many normal horses have microfilariae-- so clinical findings, hisotry, exclusion other DDX, response to treatment

* Treatment: ivermectin (moxidectin), no effective adulticide

160

What? When? Diagnosis? Treatment?

* Lice- biting and sucking

* autumn, winter (carrier animals remain infested during spring, summer and serve as source of re-infestation)

* Diagnosis: lice visualized, mane, tail (sucking), body (biting), anemia with severe sucking lice infestations

* Treatment: 2-3 treatments 2 weeks apart-- ivermectin (moxidectin) - sucking lice only OR topical insecticides

161

What are the mites that cause mange in horses?

162

Specific cause?  When? Diagnosis?

* Chorioptic mange

* mainly on distal limbs and perineum

* Entire life cycle spent on the host

* More common in winter

* Skin scrapings

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Infestations beginning on head and ears of horses and spreading to the rest of the body? Signs and symptoms? Diagnosis?

166

Causes? Diagnosis? Treatment? Prevention?

* Several causes:

- allergic- environmental allergens, drug eruptions, contact allergies, food allergies (rare) (Type I HS reaction-- allergen causes degranulation of inflammatory cells-- vasodilation usually 24-48 hours after exposure)

- common drugs causing HS reactions- penicillin, sulfa drugs, NSAIDs, phenothiazines

- physical non-immunogenic pathogenesis (rare)

* Diagnosis: systemic approach to eliminate causese (parasites, insects, drugs, vaccines, plants, feed)

* Treatment: urticaria usually resolves in 24-48 hours, corticosteroids often useful, antihistamines +/- useful, hyposensitisation- approx. 65-70% success, prolonged injection course

* Prevention: avoid cause

168

* Usually benign (grey horses)-- malignancy more common in other coloured horses but incidence rare

* Diagnosis is usually clinical

* May interfere with normal function of the surrounding structures when large

- anus

-genitalia

- upper airway

170

What is it? Different types? Cause? Diagnosis? Treatment?

* Most common tumour of equids, may appear slow growing

* Fibroblastic, non-regressing, locally invasive

* Dermis and subcutis (as lesion progresses start to involve subcutis, fascia, muscle (locally invasive and aggressive))-- can infiltrate through and along fascial planes and present distant to palpable mass

* Epidermal and dermal involvement--> variable, evolving appearance

* Different types: occult, verrucous, fibroblastic/nodular, mixed (transition)

* Cause: associated with BPV 1 and 2

* Diagnosis: biopsy, excise completely at same time if possible-- clinical diagnosis wrong about 30% of the time

Treatment: often best left alone and monitor, early recognition and treatment improves prognosis... no universally accepted best treatment....but aim to destroy all tumour cells, minimise damage to healthy tissue, excise early with complete margins-- if incomplete topical treatments a must

172

Diagnosis? Treatment? Prevention?

* Surgical excision, wide margins (but often difficult due to locations and general lack of excess skin in horses)

* Cryotherapy

* Topical 5-FU

* Intralesional cisplatin

*(Radiation therapy)

* (Piroxicam)

* Prevention- minimize UV exposure

173

Non-tumour, nodular skin disease

•Aetiology unknown, insects?

•Diagnosis

–biopsy

–Granulomatous inflammation

–eosinophils,histiocytes, some lymphocytes

•Treatment

–Surgical excision (care areas in contact with tack)

–Sublesional triamcinolone

–Systemic corticosteroids (multiple, diffuse lesions)

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Possible causes?

* Habronemiasis, Pythiosis, Nodular sarcoids, SCC, exuberant granulation tissue

* Often on distal limbs

* Diagnosis: biopsy, culture, cytology

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Dermatophilosis

182

Dermatophilosis treatment plan

184

* Circular lesions "ringworm"

* usually start around girth/axillary region

* spread over trunk, rump, dorsum, neck, head

* Lesions may be superficial or deep, may form crusts

* Diagnosis: microscopic examination of hair shafts, skin scrapings, fungal culture, wood's lamp generally not useful

* Treatment: usually self limiting and lesions resolve without treatment (can take months to regrow hair)

-- severe cases: medicated shampoos e.g. Malaseb, topical antifungal treatment/ washes (enilconazole), occasionally systemic antifungals may be needed (rare)-- Griseofulvin (NOT in pregnant mares)

185

* common- causes: dermatophilosis, folliculitis/furunculosis, etc.

186

Mange treatment in horses

* Fipronil once weekly for at least 1 month

* Other topical treatments: lime sulphur, malathion, coumaphos

* Ivermectin, moxidectin: repeat every 2 weeks for 2-3 treatments-- does not always eliminate all live mites- combine with topical treatment

* Decomntaminate fomites, environment

( Do not use Amitraz on horses- can cause irreversible ileus in horses)

188

What is atopy?

Allergic skin disease (respiratory also)

* Cross link of IgE across mast cells--> degranulation and inflammatory mediator release

(pruritis, alopecia, erythema, urticaria, papules, secondary pyoderma may develop)

* Diagnosis, treatment and prevention as for urticaria-- intradermal skin testing, serologic IgE assays (useful if owners want to pursue hyposensitisation)-- corticosteroids commonly needed, antihistamines (hydroxyzine, chlorpheniramine) +/- useful

* Hyposensitisation 65-70% success, prolonged injection course

190

Melanoma treatment?

* Do not ignore even though benign

* Monitoring may be all that is required if lesions are small

* But rapidly growing then excision (if possible)

- Cimetidine

- Intralesional cisplatin (chemotherapeutic drug)

** Vaccination - released for dogs (off label for horses but it does have a reasonable success rate e.g. reduction in the size of tumours, arrested tumour growth)

192

Sarcoid Treatment (other than surgical excision)

* Topical treatments: caustic ointments (not near an eye), XXTERRA, 5-fluorouracil (5-FU)

* Immune stimulants: imiguimod 5% cream (usually significant local reactions), BCG (intralesional)

- intralesional cisplatin (chemotherapeutic drug), electrochemotherapy

 

197

What is Pythiosis?

* Not in VIC-- in tropical, subtropical areas of the world

* Protista-fungal like organism

* Found in tropical and subtropical regions worldwide

* Horses self mutilate (pruritic)

* Ulcerates, becomes necrotic, +/- calcification, cores in fistulae (kunkers)

* Commonly on limbs, abdomen, neck, lips

* Lesions grow rapidly

* Histopath: pyogranulomatous inflammation (lots of eosinophils) surrounding organisms

* Culture- kunkers better than tissue culture

* Treatment- wide surgical excision + immunotherapy

- topical Amphotericin B, DMSO

- Difficult, expensive, euthanasia often elected

198

Habronemiasis in horses

* "Summer sores"

* Deposition by larvae flies (IH) from Habronema microstoma, Habronema muscae, or Draschia megastoma in wounds or moist skins rather than in mouth

* Histopath- granulomatous inflammation, amy not always see organisms

* Common locations include medial canthus of eye, third eyelid, distal limbs, penis/prepuce

* Treatment: ivermectin, moxidectin, corticosteroids (tapering course) may be needed to control hypersensitivity reaction

204

Cause of folliculitis/ furunculosis

* Most commonly caused by Staph and Strep spp.

* more frequent in summer

* Areas in contact with tack (saddle dermatitis), pastern dermatitis

* Invasion of commensal bacteria when skin barrier compromised

* Bacterial multiplication in hair follicles

* Rupture of hair follicles--> furunculosis and deep pyoderma

* Diagnosis: cytology (impression smear), culture, biopsy

* Treatment: Mild cases may be self- limiting but topical treatment still helpful; shampoo with dilute chlorhexidine scrub, medicated shampoos, systemic antimicrobials in severe cases (PPG, TMS)

205

* Circular lesions "ringworm"

* usually start around girth/axillary region

* spread over trunk, rump, dorsum, neck, head

* Lesions may be superficial or deep, may form crusts

* Diagnosis: microscopic examination of hair shafts, skin scrapings, fungal culture, wood's lamp generally not useful

* Treatment: usually self limiting and lesions resolve without treatment (can take months to regrow hair)

-- severe cases: medicated shampoos e.g. Malaseb, topical antifungal treatment/ washes (enilconazole), occasionally systemic antifungals may be needed (rare)-- Griseofulvin (NOT in pregnant mares)

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* common- causes: dermatophilosis, folliculitis/furunculosis, etc.

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