Equine skin disease Flashcards Preview

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Flashcards in Equine skin disease Deck (73):
1

How are equine skin diseases categorised?

Infections or non-infectious

2

List infectious equine skin diseases

- ectoparasite (infestation)
- dermatophilosis
- folliculitis
- fungal (dermatophytosis)
- viral (aural plaques)

3

Non-infectious skin diseases

- allergies
- immune-mediated
- endocrinopathies
- miscellaneous
- neoplastic

4

What ectoparasites can affect horses?

- Chorioptes spp
- Psoroptes spp
- Neotrombicula autumnalis, Demanyssus gallinae
- RARE: scabies, demodex
- Ticks, lice, fleas, flies

5

Where are chorioptes found?

limbs and tail (pastern dermatitis)

6

Where are Psoroptes spp found?

head and ears

7

What causes equine chorioptic mange?

Chorioptes bovis, especially feathered horses

8

CS - chorioptic mange

pruritus, erythema, crusts, papules,
- peaks in WINTER

9

Tx - chorioptic mange

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

10

CS - lice infestation

pruritus variable, very host specific

11

Tx - lice infestation

- fipronil spray (2tx, 10 days apart)
- synthetic pyrethroids
- systemic ivermectin

12

Dx - lice infestation

ID parasites

13

How can flies be a problem to horses?

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

14

What fly species can affect horses?

- Tabanus (horse fly)
- Stomoxys (stable fly)
- haematobia spp
- Muscids
- Culicoides spp
- Hyrotea spp.
- Hippobosca equina
- Simulium spp.

15

What causes itchy bottom?

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

16

Dx - pinworm infestatin

- handheld lens OR
- acetate tape and microscope to ID eggs

17

Tx - pinworm infestation

anthelmintics

18

What is the commonest skin allergy in horses?

sweet itch / culicoides bite hypersensitivity

19

CS - sweet itch

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

20

2 forms of sweet itch

- dorsal distributed - commonest
- ventral biting Culicoides

21

Where is sweet itch common?

- culicoides spp regions
- wet fields, little wind
- animals > 6 months

22

Ddx - sweet itch

- Oxyuris equi
- other insects
- other allergies

23

Dx - sweet itch

- clinic
- midges
- (intradermal/ serology testing of little value since they only indicate exposure)

24

Management - sweet itch

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)

25

What bacteria infect equine skin?

- Staphylococci
- Dermatophilus congolensis
- Many others

26

How are equine bacterial skin infections diagnosed?

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

27

What type of bacteria is Dermatophilus?

branching filamentous actinomycete
mainly affects ruminants and horses
varied clinical presentations

28

Describe Dermatphilus congolensis in cattle.

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

29

What is Dermatophilus associated with in temperate climes?

moisture and skin trauma

30

Colloquial names - Dermatophilosis

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

31

Where on the body is mud fever common?

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

32

What does papillomavirus infection cause in horses?

aural plaques

33

Describe aural plaques

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

34

What causes equine ringworm ?

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

35

Describe ringworm

- Healthy host - spontaneous resolution in 5-6 wks
- can be pruritic
- unsightly

36

Dx - ringworm

- same as smallies
- CS - patchy alopecia, easy epilation, hair stands on tufts
- NOT wood's lamp
- hair pluck and coat brush --> fungal culture

37

Tx - ringworm

- Nothing licensed
- topical (griseofulvin, potassium iodide)
- isolation
-- hygiene

38

List 4 horse allergies

- Culicoides hypersensitivity
- Food
- AD
- (Contact hypersensitivity)

39

List equine immune-mediated/ autoimmune diseases - 5

- 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

What may erythema multiforme look like?

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

Causes of vasculitis and erythema multiforme

- ADR
- infection
- neoplasia

42

Define PPID

= pituitary pars intermedia dysfunction = cushing's disease

43

CS - PPID/Cushing's

* hirsutism
- laminitis
- secondary infections
- supraorbital fat deposits
- hyperhydrosis

44

Tx - PPID/ Cushing's - 2

- pergolide - controls ACTH output
- trilostane - stops production of cortisol in adrenals

45

What is systemic granulomatous disease/ chronic eosinophilic enteritis?

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

46

Tx - systemic granulomatous disease/ chronic eosinophilic enteritis

- change feed
- systemic GC (months)

47

Prognosis - systemic granulomatous disease/ chronic eosinophilic enteritis

grave (spontaneous recovery described)

48

Skin signs - systemic granulomatous disease/ chronic eosinophilic enteritis

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

49

Systemic signs - systemic granulomatous disease/ chronic eosinophilic enteritis

- severe wasting
- fever
- lymphadenopathy
- icterus
- diarrhoea

50

Diagnosis - systemic granulomatous disease/ chronic eosinophilic enteritis

- hx
- cs
- leukocytosis
- anaemia
* abnormal liver/ kidney function
- skin histopath
- organ biopsy = granulomatous +/- eosinophils

51

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

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

52

3 factors required for photosensitisation

UV + poorly pigmented skin + photodynamic agent in skin

53

Types of photosensitisation

- PRIMARY - St. John's wort ingestion
- SECONDARY - liver problem and phylloerythrin

54

What happens in leucocytoclastic vasculitis?

accumulation of WVCs around BV wall --> BV destruction

55

CS - leucocytoclastic vasculitis

- nonpigmented lower limbs
- acute onset erythema, oozing, crusting, painf

56

Dx - leucocytoclastic vasculitis

biopsy (good sedation because pain)

57

Tx - leucocytoclastic vasculitis

High dose immunosuppressive therapy

58

3 categories of nodular disease

- STERILE (often harmless)
- MICROBIAL/PARASITIC
- NEOPLASTIC

59

List sterile nodular diseases

- collagenolytic granuloma
- cutaneous mastocytosis
- axillary nodular necrosis
- unilateral papillomatosis

60

List 4 microbial /parasitic nodular diseases

- Botryomycosis
- Habronemiasis
- Dermatophilosis
- Dermatophytosis

61

Describe collagenolytic granuloma

- 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

Hx - collagenolytic granuloma

- age
- speed of onset
- season
- recent tx
- systemic disease

63

Diagnostics - collagenolytic granuloma

- fungal and bacterial culture
- FNA cytology
- often histopath (definitive diagnosis)

64

Ddx - collagenolytic granuloma

THIS IS NOT AN EXHAUSTIVE LIST!:
- hypoermiasis
- papular dermatitis
- staph folliculitis and furunculosis
- dermatophytosis
- dermatophilosis
- neoplasia
- calcinosis circumscripta
- cutaneous amyloidosis

65

Tx - collagenolytic granuloma

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

66

Prognsosis - collagenolytic granuloma

- may resolve spontaneously
- recurrence common
- GCs probably ineffective in later stages after mineralisation
- Tx unlikely to produce permanent cure

67

Name the 6 types of equine sarcoid

- occult
- nodular
- verrucous
- malevolent
- mixed
- fibroblastic

68

Ddx - occult sarcoid

- dermatophytosis
- burn trauma

69

Ddx - nodular sarcocid

- fibroma
- melanoma
- collagenolytic granuloma
- warble fly cysts

70

Ddx - verrucous sarcoid

- papillomatosis
- chronic sweet itch
- SCC

71

Ddx - fibroblastic sarcoid

- GT
- botryomycosis
- habronemiasis
- neurofibroma
- SCC

72

Ddx - mixed sarcoid

- easy to recognise
- GT
- habronemiasis

73

Ddx- malevolent sarcoid

- lymphangitis
- glanders
- lymphosarcoma
- SC mycosis