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Y4 Equine - Dermatology > Dermatology introduction > Flashcards

Dermatology introduction Flashcards

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1
Q

Where is the equine skin not rich in sweat glands?

A
  • distal limbs
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2
Q

Full hair cycle length

A
  • 4-6wks
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3
Q

What does the hair coat shed depend on?

A
  • daylight hours
  • melatonin and prolactin driven
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4
Q

What phase to the hair stay in during short days and why?

A

Telogen phase - increase in melatonin and declining prolactin = winter coat growth

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5
Q

Type 1 hypersensitivity and skin example

A
  • IgE mediated involving the release of histamine by mast cell
  • biphasic in nature
  • aggregated after serial exposure
  • e.g. insect-bite hypersensitivity = sweet itch
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6
Q

Type 2 hypersensitivity and skin example

A
  • IgG mediated cytotoxic response associated with complement binding
  • e.g. Pemphigus complex
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7
Q

Type 3 hypersensitivity and skin example

A
  • Immunocomplex disposition on endothelial beds ->
  • neutrophil activation ->
  • vasculitis
  • e.g. Pastern leukocytoclastic vasculitis, purpura haemorrhagica, lupus
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8
Q

Type 4 hypersensitivity and skin example

A
  • T-cell mediated
  • cytotoxic action of T-cells
  • can be secondary to type 1
  • e.g. Insect-bite, drug eruptions
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9
Q

Affected areas in sweet itch

A
  • mane
  • tail base
  • ventral midline
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10
Q

Signs of pemphigus foliaceous

A
  • non-pruritis
  • horse becomes crusty all over
  • if catch early on may only see areas of hyperpigmentation or depigmentation and scabs
  • can be greasy
  • from the neck all the way down the back
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11
Q

What can you get with vasculitis / purpura haemorrhagica that causes lots of pain?

A
  • infarcts in the muscles
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12
Q

What can straw predispose to?

A
  • Mite infections
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13
Q

What can shavings cause?

A
  • Some can have preservatives that can cause reactions on the skin
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14
Q

Why can being near a water source be an issue?

A
  • more midges
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15
Q

Why can tack be an issue?

A
  • leather can accumulate bacteria and fungi
  • but if you clean it too much, the products used can be irritants
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16
Q

What products in feeds have cause quite a lot of reactions in horses?

A
  • Soy products, but any commercial feed has the capacity to cause reactions
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17
Q

Important details of the skin condition taken from the history

A
  • location and duration
  • localised or generalised
  • presence of pruritis
  • seasonality
  • tx attempts
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18
Q

Condition(s) associated with lesions distributed on the mane, tail and ventral line

A
  • insect bite hypersensitivity
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19
Q

Condition(s) associated with lesions distributed at the base of the tail

A
  • due to hair loss or tail rubbing
  • Oxyuris equi (pinworm)
  • insect bite hypersensitivity
  • lice infestation (although normally more truncal)
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20
Q

Condition(s) associated with lesions distributed on the chest, neck, sometimes face and in groups

A
  • fungal infections
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21
Q

Condition(s) associated with lesions distributed on the back, chest, rump and sometimes face

A
  • ‘rain scald’
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22
Q

Condition(s) associated with lesions distributed on the distal limbs

A
  • mud fever (bacterial +/- fungal)
  • mite infestation (Trombiculiasis, chorioptic mange)
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23
Q

Condition(s) associated with lesions distributed on the trunk, neck, possibly the head

A
  • urticarias
  • atopia
  • lice infestation
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24
Q

Condition(s) associated with lesions distributed on the back and girth area

A
  • contact dermatitis
  • fungal infections
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25
Lice infestations - signs
- easy to see on top of the hair in horses - often see white scaling - not just on the trunk, neck and head, i.e. on the legs as well
26
Primary lesion examples
macule, patch, papule, plaque, vesicle, pustule, wheal, nodule, tumour, abscess
27
Macule (description, size)
- circumscribed, flat impalpable area of colour change, flat - <1cm
28
Patch (description, size)
- circumscribed, flat impalpable area of colour change, flat - >1cm
29
What conditions commonly cause macules and patches?
- alopecia areata - vitiligo
30
Papule (description, size)
- solid circumscribed, raise, firm, discoloured - <1cm
31
Plaque (description, size)
- solid elevated, flat-topped, larger - >1cm
32
What conditions commonly cause papule and plaques?
- bacterial infections - fungal infections - sometimes ectoparasites
33
Vesicle (description, size)
- raised, fluid-filled, well demarcated - size is variable
34
Pustule (description, size)
- well demarcated, firm, pus-filled - size is variable
35
What conditions commonly cause vesicles and pustules?
bacterial infections, insect-bite, fungal infections
36
What bacteria causes mud fever and rain scald?
- Dermatophilus congolensis
37
Wheal (description, size, examples of common conditions)
- well-defined, raise, oval, flat-topped oedematous, no changes on overlaying skin - size variable - e.g. Urticaria, food allergies, insect sting
38
Nodule (description, size, examples of common conditions)
- raised, circumscribed solid, extending deep into dermal layer - size variable - e.g. papilloma, sarcoid, melanomas, eosinophilic granulomas, exuberant granulation tissue
39
Tumour (description, size, examples of common conditions)
- solid mass of neoplastic origin - variable size - e.g. melanomas, sarcoid, cutaneous lymphoma, fibromas, mastocytomas, histiocytoma
40
Abscess (description, size, examples of common conditions)
- demarcated, fluctuant lesion resulted from dermal or subcut accumulation of pus - variable size - e.g. Streptococcal, clostridial, C. pseudo tuberculosis, traumatic
41
Secondary lesion examples
alopecia, scales, crust, erosion, ulcer, lichenification, hypo/hyperpigmentation
42
What does a secondary lesion mean?
The condition/process has been there for a while if you see these lesions
43
Alopecia (description, size, examples of common conditions)
- partial/complete hair loss - variable size - e.g self-mutilation (pruritis), healing fungal, bacterial infections
44
Scales (description, size, examples of common conditions)
- accumulation of loose epithelial dermis - variable size - e.g. ectoparasites, pemphigus, chronic fungal/bacteria
45
Crust (description, size, examples of common conditions)
- solid, dry, adherent accumulation of serum/pus/blood/scales - variable size - e.g. chronic fungal/bacterial infection, pemphigus, chronic mites, systemic lupus
46
Erosion (description, size, examples of common conditions)
- shallow skin defect, no penetrating the basement membrane - variable size - e.g. insect-bite HS, drug reaction, 2ndary to scratching - can sometimes be a progression of vesicles (think SCC & EHV)
47
Ulcer (description, size, examples of common conditions)
- skin defect that generates the basal membrane, well-demarcated lesion - variable size - e.g. pressure sores, habronemiasis
48
Lichenification (description, size, examples of common conditions)
- thick, hard skin, hyper pigmented and alopecic - variable size - sarcoidosis, pemphigus, systemic lupus
49
Hypo/hyperpigmentation (description, size, examples of common conditions)
- area of damaged skin with changes in natural pigmentation - variable size - repeated trauma, healing fungal / fungal infection
50
Clinical patterns of horse dermatological conditions
- pruritus - crusting and scaling - ulceration and erosions - nodules - pedal or pastern dermatitis - urticaria - pigmentary abnormalities
51
Coat brushings
- ideal for ectoparasites (sucking & biting lice, harvest & feather mites) - magnification lens or microscope - use seal containers if delayed examination
52
Hair plucks
- grasping firmly with haemostats and epilating on the hair direction - similar number of hairs in anlagen and telogen
53
What do fractured hair shafts indicate?
- pruritis due to self-inflicted trauma
54
What do swollen frayed shafts with fungal spores indicate?
- dermatophytosis
55
What do ! hair bulbs indicate?
- Alopecia areata
56
Skin scrapes
- use the back of a 22 scalpel blade in the direction of the hair growth on the edge of the lesion until some ooze is obtained - ideal for mites and dermatophytes (fungi)
57
What do you need to do to skin scrapes to see mites?
- add 2 drops of mineral oil on the microscope slide
58
What do you need to do to skin scrapes to see dermatophytes?
- blue staining on microscope slide and qPCR collected in sterile containers
59
Biopsy
- excisional or punch - ideal for nodules and deep pyodermas - culture and histology
60
What can you use acetate tape to diagnose?
- Oxyrus equi: place tape on anus, then apply to microscope slide
61
FNA
- abscess or masses - culture and cytology - not done often in horses -> more likely to biopsy a mass
62
Cytology (use, stains)
- good for scrapes, cytobrushes, impression smears - diff-quick most common and easy stain - blue stain (methylene, blue/thiazine dye) -> better visualisation of hyphae - gram stain for bacteria
63
Bacterial culture (use/lesions, example)
- scrapes or minced crusts in saline - secondary with mix growth - Dermatophilus congolesis (rain scald) needs a special medium so send to lab
64
Fungal culture (use/lesions, agar, technique)
- scrapes, hair plucks, crusts - Saboureau's dextrose agar - PCR techniques (reliable and quick)
65
Different types of allergy tests
- Serum (SAT) & intradermal (IDT)
66
SAT
- unreliable -> poor sensitivity and poor PPV value cf IDT - still can provide some info but require careful interpretation along with clinical exposure - test only in acute disease (flare)
67
IDT
- better diagnostic yield cf SAT but poor repeatability - most reactions to mites, dusts, insects, plants, etc - useful to establish immunotherapy treatments

Y4 Equine - Dermatology (8 decks)

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