Equine dermatology 2 Flashcards
Neoplasia
Describe melanocytomas
- Rare
- Benign, no coat colour predilection, surgical excision is curative
- Usually young horses
What are eosinophilic granulomas in horses?
Nodular lesions commonly in saddle area, aka collagen necrosis (not histopathologically accurate)
What is the cause of eosinophilic granulomas?
- Precise cause and pathogenesis unknown
- Often occur spring and summer, so attributed to fly hypersensitivity or atopic dermatitis
- Others suggest trauma
Where do squamous cell carcinomas commonly occur?
- Face
- Eyelids/cornea/globe
- Genitalia
- Typically mucocutaneous junctions (but can be anywhere)
What are the risk factors for the development of squamous cell carcinomas?
- Susceptibility to UV light
- Smegma
Describe the spread of squamous cell carcinomas
- Can be along lymphatic chains
- Or by direct transplantation
List the treatment options for melanomas
- Benign neglect/monitoring
- Cimetidine
- Surgical removal
- Intra-lesional treatments e.g. cisplatin, mitomycin C
- Vaccines/immunotherapy
Discuss the benign neglect approach to melanomas
Standard approach, but all lesions will progres
Discuss the use of cimetidine in the treatment of melanomas
- Evidence contradictory
- Oral antacid
- Expensive, off license and need to use for some months
Discuss the use of vaccines/immunotherapy in the treatment of melanoma
- Expensive (approx £2000 for initial course, then £500/vaccine thereafter)
- Unproven efficacy
Outline the treatment of eosinophilic granuloma
- Intra- or peri-lesional steroids (methylpred or triamcinolone)
- Systemic steroids (pred or dex)
- Foam pads may be useful under saddle
- Removal difficult due to tight skin, margins difficult to achieve
List the treatment options for squamous cell carcinoma in horses
- Depends on location
- Surgical excision
- Brachytherapy
- Chemotherapy
- NSAIDs
Where would surgical excision of a squamous cell carcinoma be appropriate?
- Third eyelid
- Penile reeding/distal phallectomy
- En bloc penile resection
Outline the use of brachytherapy in the treatment of squamous cell carcinoma
- Iridium-12 very effective for periocular lesions
- Plesiotherapy (strontium-90 beta-emitter) useful for small lesions and corneal lesions
- Both only available at AHT and expensive
Outline the use of chemotherapy in the treatment of squamous cell carcinoma
- Cisplatin, 5-FU can be effective
- Mitomycin-C shown to be effective topically and intra-lesionally, often used in conjunction with surgical removal
List the treatment options for sarcoids
- Surgical removal
- Ligation
- Cryosurgery
- Immunotherapy
- Chemotherapy
- Photodynamic therapy
- Topical cytotoxic therapy
- Radiotherapy
- Imiquimod, acyclovir, bloodroot ointment, bleomycin, topical mitomycin C, taxarotene
Compare sharp and laser excision for the removal of equine sarcoids
- Sharp: smaller sarcoids e.g. nodular, but failure rate high
- Laser: higher success rate, not widely available, time to heal, looks ugly during but good once healed
Discuss the use of ligation in the treatment of equine sarcoids
- Some owners use hair tails, poor idea
- Only where can be sure there is no root
- Elastrator rings useful for some nodular and pedunculated fibroblastic sarcoids for debulking prior to treatment of source
Evaluate the use of cryosurgery in the treatment of equine sarcoids
- Only for small superficial tumours
- Time consuming
- High recurrence if not used effectively
Evaluate the use of immunotherapy in the treatment of equine sarcoids
- BCG injection for peri-ocular or fibroblastic lesions
- Not for verrucose or occult lesions
- Injected into lesions
- Care re. anaphylaxis
- Not available in UK
Discuss the use of chemotherapy in the treatment of equine sarcoids
- Intralesion injection of cytotoxic drugs e.g. cisplatin, mitomycin C, 5-fluoro uracil
- Can beeffective but danger to surgeon, not recommended
- Topical 5-FU canbe effective
- Requires heavy sedation of horse, draw up in fume cupboard etc.
How does photodynamic therapy work in the treatment of equine sarcoids?
Application of chemical to lesion leads to significant cell damage when exposed to a certain wavelength of light
Evaluate the use of photodynamic therapy in the treatment of equine sarcoids
- Poor penetration
- Only applicable to very small, superficial lesions
- Side effects when animal exposed to sunlight
What is the main topical cytotoxic therapy used in the treatment of equine sarcoids?
- AW5-LUDES (aka Liverpool cream), contains 5FU and other heavy metals
Evaluate the use of Liverpool cream in the treatment of equine sarcoids
- Reasonably effective in certain circumstances
- Requires repeated topical application by vet only, q48-72hours
- Health and safety concerns: nasty, cytotoxic, vaseline on normal skin to protect, gloves
Discuss the use of radiotherapy in the treatment of equine sarcoids
- Treatment only takes a few minutes
- Excellent cosmesis and 95% success
- Expensive
- For periocular lesions, only AHT
- Early treatment for best results
- May result in discolouration/scarring
- NO longer available in UK
Describe the method for radiotherapy treatment of equine sarcoids
- High dose brachytherapy
- high activity Iridium 192 source, emits gamma radiation
- Catheters implanted into lesion, source driven through catheters by remove afterloader
- Treatment takes a few minutes, delivered in 2 fractions a week apart
- Horse not radioactive between treatments
- No operator exposure
List the common causes of crusting and scaling in horses
- Infectious
- Dermatosis of lower limb
- Photo dermatitis
- Seborrhoea
- Localised keratinisation defects
- Immune mediated causes
- Idiopathic causes
What are the main infectious causes of crusting and scaling in horses?
- Dermatophilosis
- Dermatophytosis
- Staphylococcus spp.
Name the dermatoses of the lower limb that lead to crusting and scaling
- Leukocytoclastic vasculitis
- Pastern dermatitis
Name the localised keratinisation defects that cause crusting and scaling in horses
- Cannon keratosis
- Linear keratosis
Name the immune mediated causes of crusting and scaling in horses
- Pemphigus foliaceous (rare)
- Coronary band dystrophy (rare)
Name the idiopathic causes of crusting and scaling in horses
- Multisystemic eosinophili epitheliotrophic disease (MEED) (rare)
- Generalised granulomatous disease (sarcoidosis) (uncommon)
What conditions may allow Dermatophilosis to occur?
- Skin damage e.g. other skin disease, insect bites, environmental trauma
- Wet skin e.g. sweat, rain, washing
Which horses are at risk of dermatophilosis?
- Genetic susceptibility, some more prone
- Immunocompromised/malnourished animals
- Short lived immunity, recurrent infection likely
- Animals in contact withother infected animals (contagious)
Describe the clinical signs of dermatophilosis
- Follicular/non-follicular tufted papules, rapidly coalesce and become exudative, matted hair = paintbrush lesions
- Plucking leaves erosions/ulcerations +/- bleeding, purulent
- Commonly seen on rump and top line, saddle area, pastern, coronet, heels
- Lesions may be painful e.g. distal limb swelling, oedema, lameness
- Rarely pruritic
- Healing produces dry crusts, scaling, alopecia
Outline the methods for diagnosis of dermatophilosis
- History
- Clinical signs
- Impression smears of purulent material and cytology (G+ve branching, filamentous chain like coccus)
- Culture
- Skin biopsy
List the differential diagnoses for dermatophilus
- Staphylococcal folliculitis
- Dermatophytosis
- Pemphigus foliaceous (rare)
- Photo dermatitis (sunburn)
- Other causes of pastern dermatitis
Describe the management of dermatophilosis
- Prevent wetting
- Remove rugs to prevent sweating
- Keep tak and groowing kit clean and for individual
- Most will spontaneously regress in 1 month
- Remove and dispose of crusts carefully
- Topical or systemic treatment may be required
Describe the topical treatment of dermatophilosis
- Chlorhexidine shampoos
- Silver sulphadiazine (flammazine) cream
- Not steroids as is an infection and need immune response to clear