Equine Dermatology

Question 1

Important feature of equine skin

Answer 1

Rich in sweat glands

Question 2

Are there sweat glands in distal limbs?

Answer 2

No

Question 3

Length of hair cycle

Answer 3

4-6 weeks
(Slow, hair takes time to grow back)

Question 4

Hormones driving hair coat shedding

Answer 4

Melatonin and prolactin

Daylight driven
(Short days = increased melatonin and declining prolactin = winter coat)

Question 5

Most common hypersensitivity type (associated with sweet itch/insect bite hypersensitivity)

Answer 5

Type 1

IgE mediated/histamine release

Question 6

Hypersensitivity associated with pemphigus foliaceous

Answer 6

Type 2

IgG mediated/cytotoxic response/complement binding

Question 7

Which hypersensitivity type causes vasculitis and can happen after strangles resolution?

Answer 7

Type 3

Immune complex deposition on endothelial beds –> neutrophil activation –> vasculitis

(Pastern leukocytic vasculitis/purpura haemorrhagica/lupus)

Question 8

Hypersensitivity type related to insect bites and drug eruptions

Answer 8

Type 4

T cell mediated

Question 9

Coat brushing is good to look for…

Answer 9

Ectoparasites (sucking louse, biting louse, feather mites)

Question 10

Diagnostic technique for Oxyrus equi

Answer 10

Acetate tape (on anus)

Question 11

Culture medium for fungi

Answer 11

Saboureau’s dextrose agar

(PCR more accurate and faster)

Question 12

Two main categories of disease that cause pruritis in the horse

Answer 12

Ectoparasites
Hypersensitivities

Question 13

Conditions that have crusting and scalding

Answer 13

Rain scald
Ringworm
Photosensitisation
Pemphigus
Onchocerca

Question 14

Conditions that present as ulceration and erosions

Answer 14

Viral
Neoplasia
Pressure sores
Summer sores

Question 15

Pigmentary abnormalities in horses (2)

Answer 15

Vitiligo
Alopecia areata

Question 16

Should small masses on the horse be removed or watched?

Answer 16

Remove

Question 17

Should biopsies of masses be incisional or excisional?

Answer 17

Excisional

Question 18

Colour of horse that most commonly gets melanoma

Answer 18

Grey

Question 19

Age that melanomas typically first develop

Answer 19

4-8 years

Question 20

The four types of melanoma

Answer 20

Melanocytic nevi (single or multiple discrete nodules)
Dermal melanoma (originate in deeper dermis, small singular or multiple nodules)
Dermal melanomatosis (confluent large melanomas, increased risk of metastasis)
Malignant melanoma (rare, invasive, older horse, recurrence likely)

Question 21

Typical locations of melanomas

Answer 21

Tail, perineum, parotid region, commissure of lips/eyes

Question 22

Diagnosis of a melanoma

Answer 22

Visual inspection
Ultrasound
FNA (black pigmentation on slide)

Question 23

Likelihood of metastasis of an anaplastic malignant melanoma

Answer 23

Very high, will likely have metastasized at time of diagnosis

Question 24

Treatment options for melanomas

Answer 24

Cimetidine anti-tumour activity
Oncept (canine DNA vaccine)

Question 25

Key features of sarcoids

Answer 25

Benign
Non-metastatic
Locally aggressive
High recurrence
Affect all equids
Most common skin tumour in horse

Question 26

What is a differential for a sarcoid? (Due to similar presentation)

Answer 26

Squamous cell carcinoma

Question 27

What are the six sarcoid types?

Answer 27

Occult
Verrucose
Nodular
Fibroblastic
Mixed
Malignant

Question 28

Occult sarcoid features

Answer 28

Most mild, stable and superficial type of sarcoid
Hairless skin
Small (2-5cm) cutaneous nodule(s)
Mild hyperkeratotic region surrounding

Question 29

Verrucose sarcoid features

Answer 29

Rough hyperkeratotic appearance with flaking/scaling
Warty looking
Rarely aggressive until injured, friction/rubbing triggers change

Question 30

Nodular sarcoid features

Answer 30

Variable size (0.5-20cm)
Firm, spherical, subcutaneous nodule
Usually not an issue until injured

Type A: subcutaneous tissue only
Type B: involvement of overlying skin

Question 31

Fibroblastic sarcoid features

Answer 31

Ulcerated and fleshy
(Easily confused with injured nodular sarcoid but has ‘cauliflower appearance’)

Type 1: pedunculated with small base
Type 2: wide base, ill-defined margins

Question 32

Mixed sarcoid features

Answer 32

Transient state between verrucous/occult/nodular to fibroblastic
(Usually becoming more aggressive)

Question 33

Malignant/malevolent sarcoid features

Answer 33

Most severe and highly infiltrative (infiltration lymphatic vessels)
Often following trauma/failed treatment (–> chronic wound)
Cord of palpable tumour

Question 34

What disease can sarcoid-affected horses carry?

Answer 34

Bovine papillomavirus (BPV) type 1 and 2

Question 35

What transmits bovine papillomavirus between cows/horses (which has links with sarcoids)? What precaution should you take regarding this?

Answer 35

Fly (shouldn’t do sarcoid surgery in summer)

Question 36

Most locally invasive skin tumour in the horse?

Answer 36

Squamous cell carcinoma

Question 37

Predilection sites for squamous cell carcinomas?

Answer 37

Areas lacking pigmentation (Appaloosa/Quarter Horse/Paint)
Poorly haired areas
Mucocutaneous junctions
External genitalia

Question 38

What is the most common neoplasia of the equine eye?

Answer 38

Squamous cell carcinoma

Question 39

Predisposing factors for squamous cell carcinoma

Answer 39

Equus caballus papillomavirus 2 (EcPV2)
Flies
Smegma around genitalia
UV light

Question 40

Which sarcoids is ‘banding’ an appropriate treatment method for?

Answer 40

Sarcoids with a thin peduncle (more successful with topical treatment)

Question 41

Treatment options for sarcoids

Answer 41

Topical cream
Banding
Intralesional chemotherapy (Cisplatin in sesame oil/Mitomycin C)
Surgical excision (laser/sharp)
Electrochemotherapy
Vaccines
Radiotherapy