Equine Dermatology Cases

Question 1

What is Urticaria?

Answer 1

Mast Cell Degranulation
- Immunological
- Non-immunological
Type I and Type III Hypersensitivity
Pressure, temperature, exercise, stress, etc.
It can sometimes be recurrent – Atopic Manifestation

Question 2

How would you try to diagnose urticaria from other conditions?

Answer 2

Treatment trial

Question 3

Which treatment would be your primary choice for urticaria?

Answer 3

Corticosteroids
One off dexamethazone injection
Anti-inflammatory dose given – little risk of immunosuppression

Question 4

How else can urticaria be managed?

Answer 4

Consider any changes to management and try to correct them:
- Diet
- Bedding
- Clipping
- Flies and dust mites are often indicated – rugs and decontamination

Question 5

Case:
Scaling of face, neck and mane
Areas of hair thinning consistent with pruritus
- How would you investigate?

Answer 5

Coat brushing for ectoparasites
Biopsy

Question 6

Skin biopsy reveals: Perivascular infiltrates of eosinophils
What might this suggest?

Answer 6

Suggestive of allergic / hypersensitivity aetiology

Question 7

How can you figure out what a horse might be allergic to?

Answer 7

Intra-dermal allergy testing

Question 8

How are horses with allergies managed?

Answer 8

• Allergen specific immunotherapy, vaccine against specific allergens - Must finish the whole course
• Antihistamines may be helpful either alone or for steroid-sparing effect
• Bathing with soothing/emollient shampoos may be helpful, to remove allergens from skin surface and for symptomatic relief, e.g. Coatex Aloe and Oatmeal shampoo

Question 9

Case:
3 Week hx of stamping back legs and chewing them when lying down
Some scabs
- Which diagnostic test would we do for this horse?

Answer 9

Coat brushing

Question 10

How is Chorioptes equi treated?

Answer 10

1. Clip hair off legs – allows other treatments to be applied topically – wont remove mites
2. Inject doramectin subcutaneously – good when owners are reluctant to clip hair – very effective – need to be aware of anthelmintic resistance
3. Wash legs in selenium sulphide shampoo
4. Wash legs with an ivermectin wash – not licenced in horses
5. Apply fipronil spray to the legs – until legs are soaking wet – one big bottle would cover 4 limbs

Question 11

Case:
Episode of urticaria 6 weeks ago
Since then, skin “lumpy” and “scabby”
Horse bit quieter than normal but fine generally

• Considering the horse is very crusty, but not itchy, what is the next step?

Answer 11

• Biopsy
• Pick a scab and smear the discharge on a slide for cytology

Question 12

What must not be done before biopsying?

Answer 12

Skin scrub

Question 13

What is the most common immune mediated disease in horses?

Answer 13

Pemphigus foliaceous

Question 14

How is Pemphigus treated?

Answer 14

Corticosteroids
Azathioprine = immunosuppressant – can be used but its use requires close liver monitoring – expensive
Requires immunosuppressive doses of corticosteroids – be aware of laminitis especially in predisposed cases

Question 15

How do sarcoids present?

Answer 15

Nodular
Grow near heavy blood vessels
Location indicates diagnosis

Question 16

List the treatment options for sarcoids

Answer 16

Surgery / Cryo / Laser
‘Immune’ therapy
Cytotoxics (topical & injection)
Antimitotics (topical)
Photodynamic therapy
Radiation

Question 17

How would you manage a horse with a large fibroblastic sarcoid in the armpit region?

Answer 17

Refer?
Surgical removal required large margins – high chance of wound breakdown
High possibility of complications
GA required

Question 18

How can melanomas be treated in horses?

Answer 18

Treatment is highly owner dependent and depends on the age of the horse
Easy to surgically remove small melanomas when a horse has been given an epidural
Melanoma vaccine recommended if the melanoma is inoperable