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Dermatology > Equine skin disease > Flashcards

Equine skin disease Flashcards

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Dermatology Board Prep flashcards
1
Q

How are equine skin diseases categorised?

A

Infections or non-infectious

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2
Q

List infectious equine skin diseases

A
  • ectoparasite (infestation)
  • dermatophilosis
  • folliculitis
  • fungal (dermatophytosis)
  • viral (aural plaques)
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3
Q

Non-infectious skin diseases

A
  • allergies
  • immune-mediated
  • endocrinopathies
  • miscellaneous
  • neoplastic
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4
Q

What ectoparasites can affect horses?

A
  • Chorioptes spp
  • Psoroptes spp
  • Neotrombicula autumnalis, Demanyssus gallinae
  • RARE: scabies, demodex
  • Ticks, lice, fleas, flies
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5
Q

Where are chorioptes found?

A

limbs and tail (pastern dermatitis)

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6
Q

Where are Psoroptes spp found?

A

head and ears

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7
Q

What causes equine chorioptic mange?

A

Chorioptes bovis, especially feathered horses

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8
Q

CS - chorioptic mange

A

pruritus, erythema, crusts, papules,

- peaks in WINTER

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9
Q

Tx - chorioptic mange

A
  • challenging, often recurrent
  • clipping (especially feathered)
  • fipronil spray (repeat after 1 month)
  • avermectins (controversial efficacy)
  • permethrins/pyrethroids - flumethrin is acaricidal
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10
Q

CS - lice infestation

A

pruritus variable, very host specific

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11
Q

Tx - lice infestation

A
  • fipronil spray (2tx, 10 days apart)
  • synthetic pyrethroids
  • systemic ivermectin
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12
Q

Dx - lice infestation

A

ID parasites

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13
Q

How can flies be a problem to horses?

A
  • bites and stings
  • hypersensitivity (culicoides - sweet itch)
  • larvae (myasis)
  • disease transmission (Habronemiasis, Ochocerchiasis)
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14
Q

What fly species can affect horses?

A
  • Tabanus (horse fly)
  • Stomoxys (stable fly)
  • haematobia spp
  • Muscids
  • Culicoides spp
  • Hyrotea spp.
  • Hippobosca equina
  • Simulium spp.
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15
Q

What causes itchy bottom?

A

Pinworm infestation (oxyuriasis): Oxyuris equi adult worms migrate from terminal parts of intestines out of anus to lay eggs –> tail rubbing, self-trauma around tail base, restlessness

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16
Q

Dx - pinworm infestatin

A
  • handheld lens OR

- acetate tape and microscope to ID eggs

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17
Q

Tx - pinworm infestation

A

anthelmintics

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18
Q

What is the commonest skin allergy in horses?

A

sweet itch / culicoides bite hypersensitivity

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19
Q

CS - sweet itch

A
  • seasonal pruritus
  • excoriations
  • alopecia
  • SECONDARY LESIONS: papules, crusts, skin thickening, alopecia (primary lesions not well described)
  • Dorsal or ventral midline
  • restlessness and weight loss
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20
Q

2 forms of sweet itch

A
  • dorsal distributed - commonest

- ventral biting Culicoides

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21
Q

Where is sweet itch common?

A
  • culicoides spp regions
  • wet fields, little wind
  • animals > 6 months
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22
Q

Ddx - sweet itch

A
  • Oxyuris equi
  • other insects
  • other allergies
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23
Q

Dx - sweet itch

A
  • clinic
  • midges
  • (intradermal/ serology testing of little value since they only indicate exposure)
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24
Q

Management - sweet itch

A
  1. ) AVOIDANCE - stable 4pm-8am, rugs and hoods, fans, fly screens and traps, windy, dry grazing
  2. ) REPELLANTS AND LONG TERM INSECTICIDES: synthetic pyrethroids (cypermethrin, flumethrin, deltamethrin. Frequent administration essential)
  3. ) ANTI-INFLAMMATORIES/ANTI-PRURITIC - antihistamines and GCs (severe)
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25
Q

What bacteria infect equine skin?

A
  • Staphylococci
  • Dermatophilus congolensis
  • Many others
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26
Q

How are equine bacterial skin infections diagnosed?

A

As in small animals - cytology (pathognomic railroad tracks seen)

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27
Q

What type of bacteria is Dermatophilus?

A

branching filamentous actinomycete
mainly affects ruminants and horses
varied clinical presentations

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28
Q

Describe Dermatphilus congolensis in cattle.

A

significant economic importance in central and west affrica - severe form in cattle infested by Amblyomma variegatum tick

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29
Q

What is Dermatophilus associated with in temperate climes?

A

moisture and skin trauma

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30
Q

Colloquial names - Dermatophilosis

A

Fleece rot - sheep
Mud fever - horses (also mud rash, greasy heal, pastern folliculitis)
Rain scald - horses

31
Q

Where on the body is mud fever common?

A

lower limb very common –> irritation, foot stamping, chewing. Often chronic with scarring + secondary lesions

32
Q

What does papillomavirus infection cause in horses?

A

aural plaques

33
Q

Describe aural plaques

A
  • hyperkeratotic plaques
  • concave aspect of pinnae
  • common
  • not self-limiting (as other spp)
  • yearling +
  • Simulium spp as vectors
  • Tx = observation (doesn’t bother)
34
Q

What causes equine ringworm ?

A
  • Trichophyton equinum var equinum
  • T. mentagrophytes
  • M. equinum
  • M. gypseum
35
Q

Describe ringworm

A
  • Healthy host - spontaneous resolution in 5-6 wks
  • can be pruritic
  • unsightly
36
Q

Dx - ringworm

A
  • same as smallies
  • CS - patchy alopecia, easy epilation, hair stands on tufts
  • NOT wood’s lamp
  • hair pluck and coat brush –> fungal culture
37
Q

Tx - ringworm

A
  • Nothing licensed
  • topical (griseofulvin, potassium iodide)
  • isolation
    • hygiene
38
Q

List 4 horse allergies

A
  • Culicoides hypersensitivity
  • Food
  • AD
  • (Contact hypersensitivity)
39
Q

List equine immune-mediated/ autoimmune diseases - 5

A
  • PF
  • Erythema multiforme (not a diagnosis but an inflammation pattern)
  • ADRs
  • Vasculitis including purpura haemorrhagica - including purpura haemorrhagica (also not a diagnosis but an inflammation pattern)
  • Alopecia areata
40
Q

What may erythema multiforme look like?

A

urticaria (differentiate by histopath. also urticaria should pit on pressure then return to original shape slowly. Eryhthema multiorme conditions can be pressed down but ‘pop back up quickly’ when pressure is released.

41
Q

Causes of vasculitis and erythema multiforme

A
  • ADR
  • infection
  • neoplasia
42
Q

Define PPID

A

= pituitary pars intermedia dysfunction = cushing’s disease

43
Q

CS - PPID/Cushing’s

A
  • hirsutism
  • laminitis
  • secondary infections
  • supraorbital fat deposits
  • hyperhydrosis
44
Q

Tx - PPID/ Cushing’s - 2

A
  • pergolide - controls ACTH output

- trilostane - stops production of cortisol in adrenals

45
Q

What is systemic granulomatous disease/ chronic eosinophilic enteritis?

A
  • RARE, dramatic disease
  • skin + GIT involved
  • both grave prognosis
  • aka Equine sarcoidosis (nothing to do with sarcoids)
  • aetiology unknown
46
Q

Tx - systemic granulomatous disease/ chronic eosinophilic enteritis

A
  • change feed

- systemic GC (months)

47
Q

Prognosis - systemic granulomatous disease/ chronic eosinophilic enteritis

A

grave (spontaneous recovery described)

48
Q

Skin signs - systemic granulomatous disease/ chronic eosinophilic enteritis

A

exfoliative dermatitis = generalised scaling. often crusting, alopecia or nodules

49
Q

Systemic signs - systemic granulomatous disease/ chronic eosinophilic enteritis

A
  • severe wasting
  • fever
  • lymphadenopathy
  • icterus
  • diarrhoea
50
Q

Diagnosis - systemic granulomatous disease/ chronic eosinophilic enteritis

A
  • hx
  • cs
  • leukocytosis
  • anaemia
  • abnormal liver/ kidney function
  • skin histopath
  • organ biopsy = granulomatous +/- eosinophils
51
Q

What test should you always perform in cases of unexplained pruritus in horses?

A

Liver and kidney function (in systemic granulomatous disease/ chronic eosinophilic enteritis these results will be abnormal)

52
Q

3 factors required for photosensitisation

A

UV + poorly pigmented skin + photodynamic agent in skin

53
Q

Types of photosensitisation

A
  • PRIMARY - St. John’s wort ingestion

- SECONDARY - liver problem and phylloerythrin

54
Q

What happens in leucocytoclastic vasculitis?

A

accumulation of WVCs around BV wall –> BV destruction

55
Q

CS - leucocytoclastic vasculitis

A
  • nonpigmented lower limbs

- acute onset erythema, oozing, crusting, painf

56
Q

Dx - leucocytoclastic vasculitis

A

biopsy (good sedation because pain)

57
Q

Tx - leucocytoclastic vasculitis

A

High dose immunosuppressive therapy

58
Q

3 categories of nodular disease

A
  • STERILE (often harmless)
  • MICROBIAL/PARASITIC
  • NEOPLASTIC
59
Q

List sterile nodular diseases

A
  • collagenolytic granuloma
  • cutaneous mastocytosis
  • axillary nodular necrosis
  • unilateral papillomatosis
60
Q

List 4 microbial /parasitic nodular diseases

A
  • Botryomycosis
  • Habronemiasis
  • Dermatophilosis
  • Dermatophytosis
61
Q

Describe collagenolytic granuloma

A
  • aetiology unknown
  • saddle area, neck, flanks
  • spring and summer mostly
  • single/ multiple dermal lesions, firm, well circumscribed
  • variable diameter
  • NOT alopecic, ulcerative, painful, pruritis
  • Chronic - lesion mineralisation
62
Q

Hx - collagenolytic granuloma

A
  • age
  • speed of onset
  • season
  • recent tx
  • systemic disease
63
Q

Diagnostics - collagenolytic granuloma

A
  • fungal and bacterial culture
  • FNA cytology
  • often histopath (definitive diagnosis)
64
Q

Ddx - collagenolytic granuloma

A

THIS IS NOT AN EXHAUSTIVE LIST!:

  • hypoermiasis
  • papular dermatitis
  • staph folliculitis and furunculosis
  • dermatophytosis
  • dermatophilosis
  • neoplasia
  • calcinosis circumscripta
  • cutaneous amyloidosis
65
Q

Tx - collagenolytic granuloma

A
  • leave alone
  • Sx excision (single/few lesions
  • GCs (systemic, intralesional or sub-lesional injections
66
Q

Prognsosis - collagenolytic granuloma

A
  • may resolve spontaneously
  • recurrence common
  • GCs probably ineffective in later stages after mineralisation
  • Tx unlikely to produce permanent cure
67
Q

Name the 6 types of equine sarcoid

A
  • occult
  • nodular
  • verrucous
  • malevolent
  • mixed
  • fibroblastic
68
Q

Ddx - occult sarcoid

A
  • dermatophytosis

- burn trauma

69
Q

Ddx - nodular sarcocid

A
  • fibroma
  • melanoma
  • collagenolytic granuloma
  • warble fly cysts
70
Q

Ddx - verrucous sarcoid

A
  • papillomatosis
  • chronic sweet itch
  • SCC
71
Q

Ddx - fibroblastic sarcoid

A
  • GT
  • botryomycosis
  • habronemiasis
  • neurofibroma
  • SCC
72
Q

Ddx - mixed sarcoid

A
  • easy to recognise
  • GT
  • habronemiasis
73
Q

Ddx- malevolent sarcoid

A
  • lymphangitis
  • glanders
  • lymphosarcoma
  • SC mycosis

Dermatology (27 decks)

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