Equine Skin Diseases

Question 1

What infectious skin diseases affect horses?

Answer 1

Ectoparasite infestations
Dermatophilosis
Folliculitis
Fungal - dermatophytosis
Viral - aural plaques

Question 2

What non-infectious skin diseases affect horses?

Answer 2

Allergies
Immune-mediated
Endocrinopathies
Miscellaneous
Neoplasia

Question 3

What ectoparasites infest horses?

Answer 3

Chorioptes spp (limbs and tail)
Psoroptes spp (head and ears)
Nectrombicula autumnalis, Dermanyssus gallinae
Rarely scabies, demodecosis
Ticks, lice fleas and flies

Question 4

What are the characteristics of lice infestation in equines?

Answer 4

Infested by contact with affected animals and has variable pruritis
Can see parasites with naked eye

Question 5

What is the diagnosis and treatment for lice infestation in equines?

Answer 5

Fipronil spray, synthetic pyrethroids, systemically ivermectin

Question 6

What are the methods by which flies cause skin disease?

Answer 6

Bites and stings - wounds and pain
Hypersensitivity
Larvae causing myasis
Disease transmission of Habronemiasis or Onchocerchiasis

Question 7

What are the fly species that can cause equine skin disease?

Answer 7

Tabanus (horse fly), Stomoxys (stable fly), haematobia spp, Muscids, Culicoides spp, Hydrotea spp, Hippobosca equine, Simulium spp

Question 8

What is the pathogenesis of pin worm infestation (oxyuriasis) of horses?

Answer 8

Adult worms migrate from the terminal parts of large intestines out of anus to lay eggs resulting in tail rubbing, self-trauma around tail base and restlessness

Question 9

How is a pin worm infestation diagnosed in horses?

Answer 9

Hand-held lens or acetate tape and microscope to identify eggs

Question 10

How is a pin worm infestation treated in horses?

Answer 10

Anthelmintics

Question 11

What is the pathology of insect bite hypersensitivity in horses?

Answer 11

Type 1 hypersensitivity with seasonal pruritis, excoriations, alopecia, papules, crusts and skin thickening along dorsal or ventral midline as well as restlessness and weight loss

Question 12

What is the typical signalment of a culicoides hypersensitivity?

Answer 12

Wet fields, little wind, animals older than 6 months

Question 13

What are the DDx for a culicoides hypersensitivity?

Answer 13

Oxyuris equi, other insects, other allergies

Question 14

How is culicoides hypersensitivity diagnosed?

Answer 14

Clinic, midges, intradermal/serology

Question 15

How is sweet itch managed in horses?

Answer 15

Avoidance by stabling from 4pm to 8am, rugs/hoods, fans/fly screens/fly traps and windy dry grazing
Repellents and Longterm insecticides such as synthetic pyrethroids
Anti-inflammatories/antipruritic medication such as antihistamines and glucocorticoids

Question 16

What are common bacterial skin infections in the horse?

Answer 16

Staphylocci, Dermatophilus congolensis

Question 17

What are the key things to remember about bacterial pyoderma in horses?

Answer 17

Can be painful and pruritic

There will always be a primary cause as bacterial infection is always secondary

Question 18

What are the clinical signs of dermatophilosis in horses?

Answer 18

Exudate, matter hair, alopecia, ‘paint brush effect’

Dorsum or limbs affected

Question 19

What are the clinical signs of a papillomavirus infection?

Answer 19

Aural plaques - hyperkeratotic plaques on concave aspect of pinnae

Question 20

Which animals are affected by aural plaques?

Answer 20

Yearlings and older

Question 21

What is the therapy for aural plaques?

Answer 21

Observation

Question 22

Which dermatophytes infest horses?

Answer 22

Trichophyton equinum var equinum
T. mentagrophytes
M. equinum
M gypseum

Question 23

What is the clinical course of dermatophytosis in the horse?

Answer 23

If horse is healthy will resolve in 5-6 weeks

Can be pruritic

Question 24

What is the therapy for dermatophytosis?

Answer 24

Topical
Systemic griseofulvin/KI (off license)
Isolation and hygiene measures

Question 25

What allergies do horses suffer that can manifest at the level of the skin?

Answer 25

Culicoides hypersensitivity Food allergy - poorly understood and elimination diet difficult Atopic dermatitis Contact hypersensitivity

Question 26

What autoimmune/immune-mediated skin diseases do horses get?

Answer 26

``` Pemphigus foliaceus Erythemma multiforme Adverse drug reaction Vaculitis Alopecia areata ```

Question 27

What are the clinical signs of PPID?

Answer 27

PU/PD, lethargy, hirsutism, laminitis, secondary infections, supraorbital fat deposits, hyperdydrosis

Question 28

What is the pathogenesis of PPID?

Answer 28

Hyperplasia of the pituitary pars intermedia

Question 29

What systemic granulomatous disease affects the skin in horses?

Answer 29

Chronic eosinophilic enteritis

Question 30

What are the characteristics of chronic eosinophilic enteritis?

Answer 30

Both skin and GI involvement with grave prognosis | Equine sarcoidosis/wasting disease

Question 31

What are the proposed mechanisms of chronic eosinophilic enteritis?

Answer 31

Mycobacteria Propionibacterium Viral antigens in human sarcoidosis

Question 32

What is the treatment for chronic eosinophilic enteritis?

Answer 32

Change feed, systemic GC for months

Question 33

What are the clinical signs of chronic eosinophilic enteritis?

Answer 33

Skin signs = exfoliative dermatitis -> generalised scaling, often crusting, alopecia or nodules Systemic signs = severe wasting, fever, lymphadenopathy, icterus, diarrhoea

Question 34

How is chronic eosinophilic enteritis diagnosed?

Answer 34

History, clinical signs, leukocytosis, anaemia, abnormal liver/kidney function, skin histopathology, organ biopsy, granulomatous +/- eosinophils

Question 35

What photo-induced/influenced skin diseases are horses affected by?

Answer 35

Photosensitistion UV + poorly pigmented skin + photodynamic agent in skin such as St. Johns Wort/phenothiazine Leucocytoclastic vasculitis = non pigmented lower limbs, acute onset erythema, oozing, crusting, painful

Question 36

What sterile nodular diseases do horses get?

Answer 36

Collagenolytic granuloma Cutaneous mastocytosis Axillary nodular necrosis Unilateral papillomatosis

Question 37

Which microbial/parasitic nodular diseases do horses get?

Answer 37

Botryomycosis Habronemiasis Dermatophilosis Dermatophytosis

Question 38

What are the characteristics of collagenolytic granuloma?

Answer 38

Often in saddle area, neck and flanks mostly in spring and summer and may be single or multiple with variable diameter from 0.5-10cm Not alopecic, ulcerative, painful, pruritic Chronic lesions mineralised

Question 39

How is collagenolytic granuloma diagnosed?

Answer 39

History - age, speed on onset, seasonality, recent treatment, systemic disease Fungal and bacterial culture, FNA, often histopathology needed for definitive diagnosis

Question 40

What are the differential diagnoses for collagenolytic granuloma?

Answer 40

Hypodermiasis, papular dermatitis, Staphylococcal folliculitis and furunculosis, dermatophytosis, dermatophilosis, neoplasia, calcinosis circumscripta, cutaneous amyloidosis

Question 41

What is the treatment for collagenolytic granuloma?

Answer 41

Leave alone Surgical excision Glucocorticoids

Question 42

What is the prognosis for collagenolytic granuloma?

Answer 42

May resolve spontaneously Recurrence common Glucocorticoids probably ineffective in later stages after mineralisation

Question 43

What are the predilection sites for equine sarcoids?

Answer 43

Fly predilection sites and wounds

Question 44

What is the aetiology of equine sarcoids?

Answer 44

Viral likely - bovine papilloma virus particles identified

Question 45

What is the clinical importance of sarcoids?

Answer 45

Restricted to skin and subcutis but locally aggressive | May become large and restrict movement, ulceration and secondary infection

Question 46

What are the differential diagnoses for sarcoids?

Answer 46

Other neoplasia | Infections

Question 47

What are the six clinical sarcoid entities?

Answer 47

Occult - eyes, mouth, hairless areas Nodular - groin, sheath, eyelid, subcutaneous nodules Verrucous - face, body, nodules, thickening Fibroblastic - groin, eyelids, limbs, wounds, fleshy, ulcer Mixed - verrucous-nodular-fibroblastic, face, groin Malevolent - chords of tumour palpable

Question 48

What are the differential diagnoses for occult sarcoids?

Answer 48

Dermatophytosis | Burns trauma

Question 49

What are the differential diagnoses for nodular sarcoids?

Answer 49

Fibroma, melanoma, collagenolytic granuloma, warble fly cysts

Question 50

What are the differential diagnoses for verrucous sarcoids?

Answer 50

Papillomatosis, chronic sweet itch, squamous cell carcinoma

Question 51

What are the differential diagnoses for fibroblastic sarcoids?

Answer 51

Granulation tissue, botryomycosis, habronemiasis, neurofibroma, squamous cell carcinoma

Question 52

What are the DDx of mixed sarcoids?

Answer 52

Easy to recognised, granulation tissue, habronemiasis

Question 53

What are the DDx for malevolent sarcoids?

Answer 53

Lymphangitis, Glanders, Lymphosarcoma, subcutaneous mycosis

Question 54

How are equine sarcoids diagnosed?

Answer 54

Clinical signs rule out dermatophytosis, biopsy

Question 55

What are the pre-treatment considerations of equine sarcoids?

Answer 55

Cost, previous therapy, availability, safety, prognosis

Question 56

What are the surgical options for equine sarcoid removal?

Answer 56

Ligation, hyperthermia, electrocautery, cryosurgery, laser excision

Question 57

What topical chemotherputic agents can be used to treat equine sarcoids?

Answer 57

Cisplatin injections, 5-fluorouracil

Question 58

How is immunomodulation used to treat equine sarcoids?

Answer 58

Intralesional injection with Bacillus-Calmette-Geurin (BCG)

Question 59

What radiotherapy can be used to treat equine sarcoids?

Answer 59

Beta-radiation on smaller lesions on eyelids and joints

Question 60

What is Imiquimod (Aldara)?

Answer 60

Immune-response modifying, antiviral and anti-tumour activity, used to treat sarcoids and showing promise