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Equine Med and Surgery II > Lecture 12: Approach to Equine Dermatoses > Flashcards

Lecture 12: Approach to Equine Dermatoses Flashcards

1
Q

What are the most common causes of pruritus

A
  1. Ectoparasites- culicoides, horn and stable flies, chorioptes
  2. Allergies-atopic dermatitis
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2
Q

what are some pruritic lesions

A

alopecia, papules, pustules, urticaria

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3
Q

what is alopecia

A

traumatic hair loss

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4
Q

what causes papules

A

ectoparasites, infectious, allergies

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5
Q

what causes pustules

A

infectious

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6
Q

what causes urticaria

A

allergies

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7
Q

what ectoparasites cause diffuse ventral midline vs focal ventral midline pruritus

A

diffuse ventral midline: culicoides
Focal ventral midline: horn and stable flies

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8
Q

what ectoparasite pruritic lesions on mane and tail

A

culicoides

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9
Q

what ectoparasite causes pruritic lesions on the pattern

A

chorioptic mange

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10
Q

t or f: culicoides gnats are small, weak fliers

A

true

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11
Q

where do culicoides gnats lay their eggs

A

damp marshy areas- decaying vegetation and mature

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12
Q

culicoides gnats are blood sucking: what attracts the host

A

C02, lactic acid, octenol

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13
Q

what is the vector for onchocera cervicalis

A

culicoides gnats

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14
Q

what are the preferred feeding sites for culicoides gnats

A

top line: ears, mane, back and tail
Ventrum: diffuse

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15
Q

what doe the bites of culicoides cause

A

painful, pruritic lesions, develop into papules and wheals

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16
Q

what is a common presentation for culicoides gnats

A

rubbing mane and tail

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17
Q

what ectoparasite could cause this presentation of attacking mane, tail and diffuse on ventrum

A

culicoides gnats

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18
Q

what is tx for culicoides gnats

A
  1. Reduce population- remove manure and decaying vegetation, remove standing water
  2. Gnat traps- body temperature, contain octanol
  3. Reduce exposure- body suits, fans, ultra-fine screens, stable at night, repellents
  4. Prednisone
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19
Q

repellents containing __ are good for treating culicoides gnats

A

permethrin

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20
Q

horn flies have a large population during what time of year

A

summer months

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21
Q

T or f: horn flies are strong fliers

A

true

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22
Q

where do horn flies like to lay their eggs

A

cow manure

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23
Q

what do horn flies vector

A

protozoal disease, helminths

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24
Q

what are the preferred feeding sites for horn flies

A
  1. Ventrum in warm sunny weather, focal
  2. Top line- rainy or cool weather
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25
Q

t or f: adult horn flies rarely leave host

A

true

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26
Q

what is the presentation of horn fly bites

A

painful, pruritic, papules and wheals (central crust), focal and central midline dermatitis

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27
Q

what is the most common horn fly species in U.S.

A

H. Irritans

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28
Q

what is tx for horn flies

A
  1. Reduce population- remove decaying vegatation and manure, limit access to cattle- removal of cow manure disrupts life cycle
  2. Reduce exposure- repellents, fly predators
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29
Q

Horn flies are resistant to what type of repellents

A

pyrethroids

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30
Q

t or f: stable flies are large flies that resemble house flies

A

true

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31
Q

where doe stable flies like to lay their eggs

A

wet straw, bedding or manure (aging manure more attractive)

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32
Q

stable flies life cycle is __dependent

A

temperature dependent (4 weeks in warm weather)

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33
Q

stable flies are blood sucking and rest after meal and can be found where (vs horn flies that don’t leave host)

A

barn wall, fence, other structures

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34
Q

what do stable flies vector

A

viral disease, protozoal disease, helminths

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35
Q

what are the preferred feeding sites for stable flies

A

neck, back, chest, groin, legs

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36
Q

what are the presentation of bites from stable flies

A

painful, pruritic, papules and wheals (central crust), insect hypersensitivity

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37
Q

owner noticed many large flies biting horses- based on the location of neck and legs- what are the likely flies

A

stable flies

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38
Q

what is tx for stable flies

A
  1. Reduce population- remove moist bedding twice weekly
  2. Reduce exposure- repellents, fly predators
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39
Q

what is this?

A

chorioptes

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40
Q

what are chorioptes

A

surface mites

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41
Q

what do chorioptes feed on

A

epidermal debris

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42
Q

How Is chorioptes transmitted

A

direct and indirect (fomites) contact

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43
Q

chorioptes have larger populations and are more severe during what time of year

A

colder weather/winter

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44
Q

hot and dry conditions __survival of chorioptes

A

decrease

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45
Q

what are the most common locations for chorioptes lesions

A

feather fetlocks in draft horses, fetlocks, pastern, tail

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46
Q

based on the location of these lesions what could have caused this

A

chorioptes- feather fetlocks, pastern, tail

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47
Q

how do you dx chorioptes

A

hx, skin scrape (use insecticide), biopsy

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48
Q

what are the topical tx for chorioptes

A

lime sulfur, fipronil (front line spray), bravecto locally on pastern

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49
Q

what are the systemic tx for chorioptes

A

ivermectin, moxidectin, doramectin

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50
Q

what is atopic dermatitis

A

allergic reaction to environmental antigen

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51
Q

what type of hypersensitivity reaction is atopic dermatitis

A

1 and 4

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52
Q

what Ig’s are present in atopic dermatitis

A

IgE

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53
Q

What are the routes of exposure for atopic dermatitis

A

percutaneous, respiratory

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54
Q

what is the classic presentation for atopic dermatitis

A

age 9.5 years, seasonal, pruritus, urticaria (biggest sign), on face, pinnate, ventral thorax/abdomen, legs

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55
Q

wha is the biggest sign of atopic dermatitis

A

urticaria

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56
Q

what things do horses do that indicate atopic dermatitis

A

biting at themselves, rubbing, stomping feet, flick tails, shake head

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57
Q

what type of lesions are associated with atopic dermatitis

A

excoriations, self induced alopecia, lichenification, hyperpigmentation, secondary infection

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58
Q

based on this presentation- what is likely problem

A

atopic dermatitis

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59
Q

How do you dx atopic dermatitis

A

Hx, clinical signs, rule out ectoparasites, contact dermatitis, drug reaction, urticaria and angioedema

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60
Q

What type of testing can you do for atopic dermatitis

A
  1. Intradermal allergy testing
  2. Serology testing
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61
Q

what are some topical tx for atopic dermatitis

A
  1. Shampoos and rinses0 remove allergens and eliminate dry skin
  2. Anti pruritic agents: colloidal oatmeal, pramoxine, glucocorticoids (hydrocortisone shampoo)
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62
Q

what are some systemic tx for atopic dermatitis

A
  1. Hydroxyzine pamoate
  2. Doxepin
  3. Prednisolone
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63
Q

what are the most common causes of alopecia

A
  1. Infectious- dermatophytosis, pyoderma (staph)
  2. Follicular disease- alopecia areata
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64
Q

what is the most common dermatophyte in horses

A

trichophyton equinum

65
Q

what are the signs of dermatophytosis

A

alopecia- centrifugal ring pattern, crusts, erythema, papules

Hooves weak/splitting
+/- pruritus

66
Q

where are common locations for dermatophytosis lesions

A

areas of tack, coronary band, face, neck, dorsal lateral thorax/girth, legs

67
Q

what is the most likely cause of these lesions

A

dermatophytosis

68
Q

what is the most likely cause of these lesions

A

dermatophytosis

69
Q

t or f: woods lamp is a very helpful dx for dermatophytosis in horses

A

false

70
Q

how do you dx dermatophytosis

A
  1. Trichogram
  2. DTM add vitamin B
  3. Biopsy
71
Q

T or f: dermatophytosis may spontaneously regress in 3 months in healthy horses

A

true

72
Q

what are some topical tx for dermatophytosis

A
  1. Miconazole and chlorhexidine
  2. Ketoconazole and chlorhexidine
  3. 2% lime sulfur
73
Q

what are some systemic tx for dermatophytosis

A
  1. Griseofulvin
  2. Fluconazole
  3. Terbinafine
74
Q

what is the most common cause of pyoderma in horses

A

S. Aureus

75
Q

Folliculitis is associated with __pyoderma

A

superficial

76
Q

furunculosis is associated with __pyoderma

A

deep

77
Q

what are some clinical signs of pyoderma

A

circular alopecia-epidermal collarettes, crusts, papules, draining tracts, pruritus

78
Q

what is the most common location for staph pyoderma

A

saddle, lumbar, pastern (especially pastern)

79
Q

What is likely cause of these lesions. You performed a cytology and ruled out dermatophytosis

A

Pyoderma- likely staph

80
Q

What is likely cause of these lesions

A

pyoderma- likely staph

81
Q

what are some risk factors for developing staphylococcal pyoderma- MRSA

A

ceftiofur or aminoglycosides, large farm size, previous colonization or infection of other horses on farm, previous admission to vet hospital

82
Q

how do you dx staphylococcal pyoderma

A
  1. Culture and biopsy- if no response to empirical antibiotics
83
Q

what sign is indicative of deep pyoderma

A

draining tracts

84
Q

what is tx of staphylococcal pyoderma

A

TMS, enrofloxacin, doxycycline, topical therapy

85
Q

what is alopecia areata

A

follicular disease, non-scarring, non-inflammatory alopecia

86
Q

in alopecia areata __ and __ directed against anagen hair follicles

A

lymphocytes and antibodies

87
Q

what breeds are at risk for alopecia areata

A

appaloosas, palominos

88
Q

t or f: alopecia areata has no pruritus and is non-painful

A

true

89
Q

what lesions are associated with alopecia areata

A

focal or diffuse lesions, may spare mane and tail
On face, neck and trunk

90
Q

what is likely cause of these lesions- you noted no crusting, no inflammation, no scales and are non-painful

A

alopecia areata

91
Q

how do you dx alopecia areata

A
  1. Rule out
  2. Biopsy and histopath- peribulbar accumulation of lymphocytes, “swarm of bees”
92
Q

Appaloosas presents with skin lesions they are non-inflammatory, no crusts or scales noted and are non-painful. The following histopath was taken- what do you notice and what is likely dx

A

Follicle in anagen, lymphocytes around follicle

Dx: alopecia areata

93
Q

what is tx for alopecia areata

A

no curative tx, corticosteroids may help

94
Q

what are the differential diseases for scaling and crusting dermatoses

A
  1. Infection- dermatophilus congolensis
  2. Immune mediated: pemphigus foliaceous, sarcoidosis
  3. Keratinization defect: seborrhea
95
Q

what is the cause of dermatophilosis

A

dermatophilus congolensis

96
Q

what is the survival of dermatophilus congolensis dependent on

A

type of soil, water content

97
Q

horse presents with crusting lesions, the following histo was taken- what is cause

A

dermatophilus congolensis

98
Q

what is the pathogenesis of dermatophilosis

A
  1. Skin damage
  2. Moisture- causes release of infective, motile, flagellated zoospore
99
Q

what is the most common bacterial skin disease in large animals

A

dermatophilosis

100
Q

dermatophilosis is more prevalent in what climates

A

humid, heavy rainfall

101
Q

t or f: dermatophilosis is contagious

A

true

102
Q

what are the 4 distributions of dermatophilosis

A
  1. Rump and dorsum- run off, dribbling pattern
  2. Saddle area- under tack, increased skin trauma
  3. Face and neck- under tack, increased skin trauma
  4. Distal legs- pastern, coronets, heels
103
Q

what are some clinical signs of dermatophilosis

A

crusts, tufted papules, painful not pruritic, paintbrush lesions (thick creamy, white/yellow/green pus)

104
Q

What is likely cause of these lesions- white, crusty, creamy

A

dermatophilosis

105
Q

how do you dx dermatophilosis

A

hx, clinical signs, cytology (direct smear, saline soaked minced crusts), culture, biopsy

106
Q

what stains can you used to dx dermatophilosis

A

gram stain, diff quick, new methylene blue

107
Q

Dermatophilosis often regress with __weather within 4 weeks

A

dry

108
Q

what are some topical tx for dermatophilosis

A

iodophors, lime sulfa, chlorhexidine

109
Q

what antibiotics are used to tx dermatophilosis

A

TMS, penicillin/streptomycin

110
Q

what is the most common equine auto-immune skin disease

A

pemphigus foliaceous

111
Q

in pemphigus foliaceous antibodies target __

A

transmembrane protein antigens

112
Q

what is the distribution for pemphigus foliaceous clinical signs

A

face, trunk, coronary bands, edema of legs/ventral abdomen

113
Q

what may be the first sign of pemphigus foliaceous

A

edema of legs/ventral abdomen

114
Q

what are some clinical signs of pemphigus foliaceous

A

exfoliative, scaling, crusting, urticaria, edema

115
Q

what autoimmune disease likely caused this presentation. You also noted lesions at the coronary band and edema of the trunk/legs

A

pemphigus foliaceous

116
Q

how do you dx pemphigus foliaceous

A

hx, clinical signs, cytology, biopsy

117
Q

what do you expect to see on cytology of pemphigus foliaceous

A

acantholytic keratinocytes, non-degenerative neutrophils

118
Q

horse presents with scaling on face and coronary band- cytology showed this- what is arrow pointing at and what is likely cause n

A

Arrow: acantholytic keratinocytes
Dx: pemphigus foliaceous

119
Q

what is tx for pemphigus foliaceous

A
  1. Prednisolone
  2. Dexamethasone
  3. Azathioprine
  4. Aurothioglucose
120
Q

what are some adverse effects of azathioprine

A

bone marrow suppression- increase susceptibility to infection

121
Q

what are some adverse effects of gold salts

A

bone marrow suppression, glomerulonephropathy

122
Q

what is sarcoidosis

A

idiopathic, generalized, systemic granulomatous disease

123
Q

what signs are seen with sarcoidosis

A

exfoliative dermatitis, severe wasting, sarcoidosis granulomatous inflammation

124
Q

in sarcoidosis skin lesions occur first followed by ___

A

internal organ involvement (lungs, GIT)

125
Q

horse presents with severe emaciation and these lesions are present- what is likely cause

A

sarcoidosis

126
Q

how do you dx sarcoidosis

A

hx, clinical signs, biopsy

127
Q

what is the prognosis for skin disease vs GI involvement for sarcoidosis

A

skin dz only- better prognosis
GI involvement: poor prognosis

128
Q

what is tx for sarcoidosis

A
  1. Prednisolone
  2. Omega 6/3 fatty acids
  3. Pentoxifyline
129
Q

is equine pastern dermatitis a disease or syndrome

A

syndrome

130
Q

what is a predisposing factor for equine pastern dermatitis in draft horses

A

feathering over fetlocks

131
Q

in equine pastern dermatitis the __aspect of the pastern is more affected

A

caudal

132
Q

what is the mild form of equine pastern dermatitis

A

scratches, mud fever, mud rash

133
Q

what is the exudative form of equine pastern dermatitis

A

grease heel, dew poisoning

134
Q

what is the chronic proliferative form of equine pastern dermatitis

A

grapes, verrucous pododermatitis

135
Q

what signs are associated with equine pastern dermatitis mild form

A

alopecia, dry scale, crusts, epidermal hyperplasia, variable pruritus and pain

136
Q

what signs are seen with exudative form of equine pastern dermatitis

A

erythema, erosion, alopecia, serous to purple T crusts, epidermolysis, vasculitis

137
Q

what is see with chronic proliferative form of equine pastern dermatitis

A

excessive granulation tissue, nodular hyperkeratosis, lichenification, fissures, painful, lameness

138
Q

what form of equine pastern dermatitis is this

A

Chronic proliferative form

139
Q

what for of equine pastern dermatitis is this

A

mild form

140
Q

what form of equine pastern dermatitis is this

A

Exudative form

141
Q

how do you dx equine pastern dermatitis

A
  1. Superficial skin scrape
  2. Cytology
  3. Trichogram
  4. DTM
  5. Biopsy
  6. Culture/deep tissue culture
  7. CBC/chem
142
Q

what is chronic progressive lymphedema and who is most commonly affected

A

defect in dermal and lymphatic elastin fibers

Draft horses

143
Q

what are the early signs of chronic progressive lymphedema

A

swelling and scaling

144
Q

what are the progressive signs of chronic progressive lymphedema

A

lower leg enlargement due to firm swelling, thickened skin fields, large firm nodules

145
Q

draft horse presents with a lot of limb swelling and nodules. What is likely cause

A

chronic progressive lymphedema

146
Q

how do you dx chronic progressive lymphedema

A

hx, clinical signs, cytology, biopsy

147
Q

what is tx for chronic progressive lymphedema

A

no curative tx, palliative care

148
Q

what is photosensitivity

A

increased susceptibility to damaging effects of UVL

149
Q

what is phototoxicity

A

sunburn reaction, dose related response to light exposure

150
Q

UV_ less than __nm is not damaging to cells

A

UVC, less than 290nm

151
Q

UB_, ___-___nm results in sunburn or erythema spectrum

A

UVB, 290-320

152
Q

UV__, __-___nm penetrates deeper and associated with photosensitivities

A

UVA, 320-400nm

153
Q

what are the 3 basic features of photosensitivity

A
  1. Photodynamic agent
  2. Exposure to sufficient amounts of UVL
  3. Cutaneous absoprtion- lack of pigment in hair and skin
154
Q

what are some examples photodynamic agents

A

Plants: St. John’s worts, buck wheat

Mycotoxins

Drugs/chemicals: phenothiazines

155
Q

what is primary photosensitivity

A

photodynamic agent ingested

156
Q

what is hematogenous photosensitivity

A

hepatotoxic plant

157
Q

you go to farm to evaluate these lesions and notice a lot of St. John wort plants. What likely caused these lesions

A

Photosensitivity reaction

158
Q

how do you dx photosensitivity

A

Hx, look for plants, lesions, CBC/chem-liver abnormalities

159
Q

what is tx for photosensitivity

A
  1. Eliminate photodynamic agents
  2. Avoidance of sunlight
  3. Tx hepatic disease
  4. Tx secondary infection
  5. Glucocorticoids
  6. NSAIDS

Equine Med and Surgery II (15 decks)

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