Lecture 12: Approach to Equine Dermatoses Flashcards
1
Q
What are the most common causes of pruritus
A
- Ectoparasites- culicoides, horn and stable flies, chorioptes
- Allergies-atopic dermatitis
2
Q
what are some pruritic lesions
A
alopecia, papules, pustules, urticaria
3
Q
what is alopecia
A
traumatic hair loss
4
Q
what causes papules
A
ectoparasites, infectious, allergies
5
Q
what causes pustules
A
infectious
6
Q
what causes urticaria
A
allergies
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
8
Q
what ectoparasite pruritic lesions on mane and tail
A
culicoides
9
Q
what ectoparasite causes pruritic lesions on the pastern
A
chorioptic mange
10
Q
t or f: culicoides gnats are small, weak fliers
A
true
11
Q
where do culicoides gnats lay their eggs
A
damp marshy areas- decaying vegetation and mature
12
Q
culicoides gnats are blood sucking: what attracts the host
A
C02, lactic acid, octenol
13
Q
what is the vector for onchocera cervicalis
A
culicoides gnats
14
Q
what are the preferred feeding sites for culicoides gnats
A
top line: ears, mane, back and tail
Ventrum: diffuse
15
Q
what doe the bites of culicoides cause
A
painful, pruritic lesions, develop into papules and wheals
16
Q
what is a common presentation for culicoides gnats
A
rubbing mane and tail
17
Q
what ectoparasite could cause this presentation of attacking mane, tail and diffuse on ventrum
A
culicoides gnats
18
Q
what is tx for culicoides gnats
A
- Reduce population- remove manure and decaying vegetation, remove standing water
- Gnat traps- body temperature, contain octanol
- Reduce exposure- body suits, fans, ultra-fine screens, stable at night, repellents
- Prednisone
19
Q
repellents containing __ are good for treating culicoides gnats
A
permethrin
20
Q
horn flies have a large population during what time of year
A
summer months
21
Q
T or f: horn flies are strong fliers
A
true
22
Q
where do horn flies like to lay their eggs
A
cow manure
23
Q
what do horn flies vector
A
protozoal disease, helminths
24
Q
what are the preferred feeding sites for horn flies
A
- Ventrum in warm sunny weather, focal
- Top line- rainy or cool weather
25
t or f: adult horn flies rarely leave host
true
26
what is the presentation of horn fly bites
painful, pruritic, papules and wheals (central crust), focal and central midline dermatitis
27
what is the most common horn fly species in U.S.
H. Irritans
28
what is tx for horn flies
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
29
Horn flies are resistant to what type of repellents
pyrethroids
30
t or f: stable flies are large flies that resemble house flies
true
31
where doe stable flies like to lay their eggs
wet straw, bedding or manure (aging manure more attractive)
32
stable flies life cycle is __dependent
temperature dependent (4 weeks in warm weather)
33
stable flies are blood sucking and rest after meal and can be found where (vs horn flies that don’t leave host)
barn wall, fence, other structures
34
what do stable flies vector
viral disease, protozoal disease, helminths
35
what are the preferred feeding sites for stable flies
neck, back, chest, groin, legs
36
what are the presentation of bites from stable flies
painful, pruritic, papules and wheals (central crust), insect hypersensitivity
37
owner noticed many large flies biting horses- based on the location of neck and legs- what are the likely flies
stable flies
38
what is tx for stable flies
1. Reduce population- remove moist bedding twice weekly
2. Reduce exposure- repellents, fly predators
39
what is this?
chorioptes
40
what are chorioptes
surface mites
41
what do chorioptes feed on
epidermal debris
42
How Is chorioptes transmitted
direct and indirect (fomites) contact
43
chorioptes have larger populations and are more severe during what time of year
colder weather/winter
44
hot and dry conditions __survival of chorioptes
decrease
45
what are the most common locations for chorioptes lesions
feather fetlocks in draft horses, fetlocks, pastern, tail
46
based on the location of these lesions what could have caused this
chorioptes- feather fetlocks, pastern, tail
47
how do you dx chorioptes
hx, skin scrape (use insecticide), biopsy
48
what are the topical tx for chorioptes
lime sulfur, fipronil (front line spray), bravecto locally on pastern
49
what are the systemic tx for chorioptes
ivermectin, moxidectin, doramectin
50
what is atopic dermatitis
allergic reaction to environmental antigen
51
what type of hypersensitivity reaction is atopic dermatitis
1 and 4
52
what Ig’s are present in atopic dermatitis
IgE
53
What are the routes of exposure for atopic dermatitis
percutaneous, respiratory
54
what is the classic presentation for atopic dermatitis
age 9.5 years, seasonal, pruritus, urticaria (biggest sign), on face, pinnate, ventral thorax/abdomen, legs
55
wha is the biggest sign of atopic dermatitis
urticaria
56
what things do horses do that indicate atopic dermatitis
biting at themselves, rubbing, stomping feet, flick tails, shake head
57
what type of lesions are associated with atopic dermatitis
excoriations, self induced alopecia, lichenification, hyperpigmentation, secondary infection
58
based on this presentation- what is likely problem
atopic dermatitis
59
How do you dx atopic dermatitis
Hx, clinical signs, rule out ectoparasites, contact dermatitis, drug reaction, urticaria and angioedema
60
What type of testing can you do for atopic dermatitis
1. Intradermal allergy testing
2. Serology testing
61
what are some topical tx for atopic dermatitis
1. Shampoos and rinses0 remove allergens and eliminate dry skin
2. Anti pruritic agents: colloidal oatmeal, pramoxine, glucocorticoids (hydrocortisone shampoo)
62
what are some systemic tx for atopic dermatitis
1. Hydroxyzine pamoate
2. Doxepin
3. Prednisolone
63
what are the most common causes of alopecia
1. Infectious- dermatophytosis, pyoderma (staph)
2. Follicular disease- alopecia areata
64
what is the most common dermatophyte in horses
trichophyton equinum
65
what are the signs of dermatophytosis
alopecia- centrifugal ring pattern, crusts, erythema, papules
Hooves weak/splitting
+/- pruritus
66
where are common locations for dermatophytosis lesions
areas of tack, coronary band, face, neck, dorsal lateral thorax/girth, legs
67
what is the most likely cause of these lesions
dermatophytosis
68
what is the most likely cause of these lesions
dermatophytosis
69
t or f: woods lamp is a very helpful dx for dermatophytosis in horses
false
70
how do you dx dermatophytosis
1. Trichogram
2. DTM add vitamin B
3. Biopsy
71
T or f: dermatophytosis may spontaneously regress in 3 months in healthy horses
true
72
what are some topical tx for dermatophytosis
1. Miconazole and chlorhexidine
2. Ketoconazole and chlorhexidine
3. 2% lime sulfur
73
what are some systemic tx for dermatophytosis
1. Griseofulvin
2. Fluconazole
3. Terbinafine
74
what is the most common cause of pyoderma in horses
S. Aureus
75
Folliculitis is associated with __pyoderma
superficial
76
furunculosis is associated with __pyoderma
deep
77
what are some clinical signs of pyoderma
circular alopecia-epidermal collarettes, crusts, papules, draining tracts, pruritus
78
what is the most common location for staph pyoderma
saddle, lumbar, pastern (especially pastern)
79
What is likely cause of these lesions. You performed a cytology and ruled out dermatophytosis
Pyoderma- likely staph
80
What is likely cause of these lesions
pyoderma- likely staph
81
what are some risk factors for developing staphylococcal pyoderma- MRSA
ceftiofur or aminoglycosides, large farm size, previous colonization or infection of other horses on farm, previous admission to vet hospital
82
how do you dx staphylococcal pyoderma
1. Culture and biopsy- if no response to empirical antibiotics
83
what sign is indicative of deep pyoderma
draining tracts
84
what is tx of staphylococcal pyoderma
TMS, enrofloxacin, doxycycline, topical therapy
85
what is alopecia areata
follicular disease, non-scarring, non-inflammatory alopecia
86
in alopecia areata __ and __ directed against anagen hair follicles
lymphocytes and antibodies
87
what breeds are at risk for alopecia areata
appaloosas, palominos
88
t or f: alopecia areata has no pruritus and is non-painful
true
89
what lesions are associated with alopecia areata
focal or diffuse lesions, may spare mane and tail
On face, neck and trunk
90
what is likely cause of these lesions- you noted no crusting, no inflammation, no scales and are non-painful
alopecia areata
91
how do you dx alopecia areata
1. Rule out
2. Biopsy and histopath- peribulbar accumulation of lymphocytes, “swarm of bees”
92
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
Follicle in anagen, lymphocytes around follicle
Dx: alopecia areata
93
what is tx for alopecia areata
no curative tx, corticosteroids may help
94
what are the differential diseases for scaling and crusting dermatoses
1. Infection- dermatophilus congolensis
2. Immune mediated: pemphigus foliaceous, sarcoidosis
3. Keratinization defect: seborrhea
95
what is the cause of dermatophilosis
dermatophilus congolensis
96
what is the survival of dermatophilus congolensis dependent on
type of soil, water content
97
horse presents with crusting lesions, the following histo was taken- what is cause
dermatophilus congolensis
98
what is the pathogenesis of dermatophilosis
1. Skin damage
2. Moisture- causes release of infective, motile, flagellated zoospore
99
what is the most common bacterial skin disease in large animals
dermatophilosis
100
dermatophilosis is more prevalent in what climates
humid, heavy rainfall
101
t or f: dermatophilosis is contagious
true
102
what are the 4 distributions of dermatophilosis
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
what are some clinical signs of dermatophilosis
crusts, tufted papules, painful not pruritic, paintbrush lesions (thick creamy, white/yellow/green pus)
104
What is likely cause of these lesions- white, crusty, creamy
dermatophilosis
105
how do you dx dermatophilosis
hx, clinical signs, cytology (direct smear, saline soaked minced crusts), culture, biopsy
106
what stains can you used to dx dermatophilosis
gram stain, diff quick, new methylene blue
107
Dermatophilosis often regress with __weather within 4 weeks
dry
108
what are some topical tx for dermatophilosis
iodophors, lime sulfa, chlorhexidine
109
what antibiotics are used to tx dermatophilosis
TMS, penicillin/streptomycin
110
what is the most common equine auto-immune skin disease
pemphigus foliaceous
111
in pemphigus foliaceous antibodies target __
transmembrane protein antigens
112
what is the distribution for pemphigus foliaceous clinical signs
face, trunk, coronary bands, edema of legs/ventral abdomen
113
what may be the first sign of pemphigus foliaceous
edema of legs/ventral abdomen
114
what are some clinical signs of pemphigus foliaceous
exfoliative, scaling, crusting, urticaria, edema
115
what autoimmune disease likely caused this presentation. You also noted lesions at the coronary band and edema of the trunk/legs
pemphigus foliaceous
116
how do you dx pemphigus foliaceous
hx, clinical signs, cytology, biopsy
117
what do you expect to see on cytology of pemphigus foliaceous
acantholytic keratinocytes, non-degenerative neutrophils
118
horse presents with scaling on face and coronary band- cytology showed this- what is arrow pointing at and what is likely cause n
Arrow: acantholytic keratinocytes
Dx: pemphigus foliaceous
119
what is tx for pemphigus foliaceous
1. Prednisolone
2. Dexamethasone
3. Azathioprine
4. Aurothioglucose
120
what are some adverse effects of azathioprine
bone marrow suppression- increase susceptibility to infection
121
what are some adverse effects of gold salts
bone marrow suppression, glomerulonephropathy
122
what is sarcoidosis
idiopathic, generalized, systemic granulomatous disease
123
what signs are seen with sarcoidosis
exfoliative dermatitis, severe wasting, sarcoidosis granulomatous inflammation
124
in sarcoidosis skin lesions occur first followed by ___
internal organ involvement (lungs, GIT)
125
horse presents with severe emaciation and these lesions are present- what is likely cause
sarcoidosis
126
how do you dx sarcoidosis
hx, clinical signs, biopsy
127
what is the prognosis for skin disease vs GI involvement for sarcoidosis
skin dz only- better prognosis
GI involvement: poor prognosis
128
what is tx for sarcoidosis
1. Prednisolone
2. Omega 6/3 fatty acids
3. Pentoxifyline
129
is equine pastern dermatitis a disease or syndrome
syndrome
130
what is a predisposing factor for equine pastern dermatitis in draft horses
feathering over fetlocks
131
in equine pastern dermatitis the __aspect of the pastern is more affected
caudal
132
what is the mild form of equine pastern dermatitis
scratches, mud fever, mud rash
133
what is the exudative form of equine pastern dermatitis
grease heel, dew poisoning
134
what is the chronic proliferative form of equine pastern dermatitis
grapes, verrucous pododermatitis
135
what signs are associated with equine pastern dermatitis mild form
alopecia, dry scale, crusts, epidermal hyperplasia, variable pruritus and pain
136
what signs are seen with exudative form of equine pastern dermatitis
erythema, erosion, alopecia, serous to purple T crusts, epidermolysis, vasculitis
137
what is see with chronic proliferative form of equine pastern dermatitis
excessive granulation tissue, nodular hyperkeratosis, lichenification, fissures, painful, lameness
138
what form of equine pastern dermatitis is this
Chronic proliferative form
139
what for of equine pastern dermatitis is this
mild form
140
what form of equine pastern dermatitis is this
Exudative form
141
how do you dx equine pastern dermatitis
1. Superficial skin scrape
2. Cytology
3. Trichogram
4. DTM
5. Biopsy
6. Culture/deep tissue culture
7. CBC/chem
142
what is chronic progressive lymphedema and who is most commonly affected
defect in dermal and lymphatic elastin fibers
Draft horses
143
what are the early signs of chronic progressive lymphedema
swelling and scaling
144
what are the progressive signs of chronic progressive lymphedema
lower leg enlargement due to firm swelling, thickened skin fields, large firm nodules
145
draft horse presents with a lot of limb swelling and nodules. What is likely cause
chronic progressive lymphedema
146
how do you dx chronic progressive lymphedema
hx, clinical signs, cytology, biopsy
147
what is tx for chronic progressive lymphedema
no curative tx, palliative care
148
what is photosensitivity
increased susceptibility to damaging effects of UVL
149
what is phototoxicity
sunburn reaction, dose related response to light exposure
150
UV_ less than __nm is not damaging to cells
UVC, less than 290nm
151
UB_, ___-___nm results in sunburn or erythema spectrum
UVB, 290-320
152
UV__, __-___nm penetrates deeper and associated with photosensitivities
UVA, 320-400nm
153
what are the 3 basic features of photosensitivity
1. Photodynamic agent
2. Exposure to sufficient amounts of UVL
3. Cutaneous absoprtion- lack of pigment in hair and skin
154
what are some examples photodynamic agents
Plants: St. John’s worts, buck wheat
Mycotoxins
Drugs/chemicals: phenothiazines
155
what is primary photosensitivity
photodynamic agent ingested
156
what is hepatogenous photosensitivity
hepatotoxic plant
157
you go to farm to evaluate these lesions and notice a lot of St. John wort plants. What likely caused these lesions
Photosensitivity reaction
158
how do you dx photosensitivity
Hx, look for plants, lesions, CBC/chem-liver abnormalities
159
what is tx for photosensitivity
1. Eliminate photodynamic agents
2. Avoidance of sunlight
3. Tx hepatic disease
4. Tx secondary infection
5. Glucocorticoids
6. NSAIDS
