Small Animal Dermatology Flashcards
(153 cards)
1
Q
Common pruritic skin diseases
A
Parasites- cheyletiella, sarcoptes, trombicula
Microbes- staphylococci, malassezia
Hypersensitivity- food allergy, flea allergic dermatitis, atopic dermatitis
2
Q
What are the characteristics of trombiculiasis?
A
Strictly seasonal- July to Sept/Oct
Can be asymptomatic to severely pruritic (hypersensitivity reaction)
No tx licensed- use fipronil
3
Q
What are the characteristics of cheyletiellosis?
A
Walking dandruff, primarily on the dorsal trunk. Ranges from mild to severe pruritus. Zoonotic.
No tx licensed- amitraz, fipronil, selamectin, ivermectin, moxidectin
4
Q
What are the characteristics of demodecosis?
A
Juvenile onset, localised- recovers spontaneously
Juvenile onset, generalised- inherited predisposition
Adult onset, localised/ generalised- >2YO, immunosuppression (drugs- GC, endocrine dz, neoplasia)
5
Q
What are the tx options for demodecosis?
A
Imidacloprid/ moxidectin (Advocate), aludex wash (amitraz), promeris duo (metaflumizone and amitraz).
Off license- ivermectin, milbemycin
Minimum of 12wks
6
Q
What are the characteristics of sarcoptes?
A
Intensely pruritic. Crusted papules. Doesn’t respond well to steroids- escalating doses. Zoonotic
7
Q
How is flea bite hypersensitivity diagnosed?
A
Hx and clinical signs- age of onset commonly 3-5yr, seasonal, lumbosacral
Presence of fleas/ flea f+
Response to therapy
Allergy testing- ID, serology
8
Q
How is flea bite hypersensitivity managed?
A
Rolls Royce flea control
Antipruritic/ anti-inflammatory- glucocorticoids, (antihistamines, EFA)
9
Q
What are the characteristics of atopic dermatitis?
A
Hypersensitivity to environmental allergens
Delayed (type IV, cell mediated) and immediate (type I, IgE-mediated) hypersensitivity
10
Q
How is atopic dermatitis diagnosed?
A
Dx of exclusion- r/o ectoparasitic dz and skin infections. Investigate hypersensitivity to food.
5 of below criteria increase likelihood of dx- age of onset, mostly indoor, corticosteroid-responsive pruritus, chronic/ recurrent yeast infections, affected front feet, affected pinnae, non affected ear margins, non affected dorso-lumbar area
11
Q
How is atopic dermatitis managed?
A
Control of 2ry infections, skin barrier improvement, avoidance of trigger factors, allergen-specific immunotherapy, anti-pruritic/ anti-inflammatories.
12
Q
What is urticaria cf angioedema?
A
Urticaria- multiple wheals- circumscribed raised lesions caused by dermal oedema
Angioedema- marked localised subcutaneous oedema
Clinical sign not a dz
13
Q
How do you distinguish urticarial/ angioedema from other lumps?
A
They are transient- come and go
14
Q
What are some trigger factors for urticarial/ angiodema
A
Allergens- aero-, contact, environmental Parasites, insect bites/ stings Drugs Systemic dz Dietary components Idiopathic
15
Q
How is a food hypersensitivity diagnosed?
A
Hx and signs
Response to restricted diet and relapse on old diet
Intradermal and serology of no benefit
16
Q
How is a food hypersensitivity managed?
A
Avoidance of allergen
Treat 2ry complications
Glucocorticoids if allergen avoidance not possible, may need steroids initially to get allergy under control
17
Q
Why are ear infections associated with atopic dermatitis?
A
Immunological derangement. Cutaneous abnormalities e.g. due to pruritus.
Organisms- staph. pseudointermedius, malassezia
18
Q
Scale vs Crust
A
Scale- accumulation of loose cornified fragments of the stratum corneum
Exudate- presence of dried exudate on skin surface
19
Q
What are some causes of scaling?
A
Defect of cornification- 1ry or 2ry
2ry- parasites, infection, nutrition, allergy, neoplasia
1ry- idiopathic, genetic
20
Q
What is sebaceous adenitis?
A
Sebaceous glands destroyed.
21
Q
How is sebaceous adenitis diagnosed and treated?
A
Exclude 2ry causes, bx
Tx- shampoo, EFA, cyA
22
Q
What is spaniel seborrhoea?
A
Primary defect in cocker spaniels. Incr mitotic rate/ decr turnover time
23
Q
What are the tx options for sarcoptes?
A
Amitraz weekly for 6 weeks. Or selamectin or advocate (imidacloprid/ moxidectin)
Prednisolone to limit extreme pruritus- often refractory to steroids
24
Q
What is supf necrolytic dermatitis?
A
Uncommon, erosive, crusting, ulcerative dz which commonly affects the footpads, extremities and periorifical skin of middle and old aged dogs. Seen with hepatic dz or pancreatic gluconoma
25
What bacteria are commonly involved in pyoderma?
Staph pseudintermedius. Other G+ves (e.g. streptococci).
| G-ves- coliforms, pseudomonas, proteus
26
How is pyoderma diagnosed?
Hx- recurrent pyoderma, response to abx
Clinical signs- papules, pustules, epidermal collarettes, draining sinuses
Cytology- tape strip, impression smear
Search for underlying cause
27
What are the 3 types of pyoderma and the causes of each?
Surface- hot spot, mucocutaneous pyoderma, bacterial overgrowth, intertrigo
Superficial- spf pyoderma, impetigo
Deep- furunculosis, acne, bacterial granuloma
28
What is a hot spot?
Acute, self trauma due to underlying pruritic problem e.g. flea allergy, anal irritation, otitis
29
What is the tx for a hot spot?
Topical abx
Antiinflammatory depending on severity
Tx underlying cause
30
What is impetigo?
Spf pyoderma of puppies. Pustules in interfollicular epidermis, ventral abdomen. Responds to topical abx
31
What is the typical presentation of spf pyoderma?
>90% s.pseudintermedius. Typically ventral abdomen and trunk. Often recurrent and pruritic. Macule, papule, pustule, epidermal collarettes
32
What are the characteristics of deep pyoderma?
Underlying cause- as for spf pyoderma, demodecosis
| S. Pseudintermedius (60-80%), G-ves, anaerobes
33
How is deep pyoderma diagnosed and treated?
Bacterial culture always indicated, cytology, skin scrapes etc, blood tests, imaging for underlying cause
Tx- based on cytology until culture results
34
What is acne?
A form of deep pyoderma. Often localised to the chin. Occurs in young animals. May be due to a keratinisation defect. Other causes in cats incl demodecosis, dermatophytosis, FeLV, FIV, allergies
35
What are the rules of thumb for treating pyoderma?
Spf- 3 weeks or 1wk beyond clinical cure
Deep- 4-6wks or 2wks beyond clinical cure
Until underlying trigger addressed
36
What are the 4 principle mechanisms of alopecia?
Self-trauma
Inflammatory destruction
Hair growth cycle affected
Hair dystrophy/ dysplasia/ atrophy/ malformation
37
How do you approach alopecia?
R/o traumatic hair loss (due to pruritus). R/o inflammatory causes- investigate demodecosis, bacterial folliculitis, dermatophytosis. Then consider endocrine dz. Then miscellaneous causes.
38
What are the causes of folliculitis (inflammatory alopecia)?
Parasitic- demodex
Bacterial- staphylococci
Fungal- dermatophytosis
39
What is alopecia X?
Unclear aetiology, no consistent abnormalities. Well in themselves. Cosmetic problem only.
40
What are the causes of acquired non traumatic alopecia?
Endocrinopathies
| Coat color linked, miscellaneous hair cycle/ growth problems e.g. recurrent flank alopecia
41
What are the causes of nodules?
Cutaneous neoplasia
Inflammatory process
Trauma (haematoma)
Depositional dz (amyloidosis)
42
What is the diagnostic approach to neoplasia?
Dx of tumor type, histological grade, staging
| FNA and skin bx- should be done routinely in nodular dz
43
What are the clinical signs of a MCT?
Varies. Single/multiple, small/large, well demarcated/ infiltrative, firm/soft, ulcerated/epithelialised, oedematous/ inflamm
Incr tendency to occur on back half of body incl perineum, distal limbs and prepuce.
May incl bleeding disorders, IMTP, GI ulceration
44
What substances do MCTs release?
Histamine
Heparin
Other vasoactive amines
45
How are MCTs graded?
By histopathology- mitotic rate, degree of differentiation, tissue invasion
46
How are MCTs staged?
By anatomical location, clinical and cytological assessment of LNs, imaging of liver and spleen
47
What is the tx of choice for MCTs?
Sx- minimum of 2cm lateral margins and one deep facial plane. Should be examined histologically for completeness of excision
Adjunctive chemo if high grade tumour
48
What is a histiocytoma?
Tumor of Langerhans cells (APCs), generally benign, may migrate to LNs. Pinnae, face or feet. Generally resolve due to lymphocyte driven cell mediated response. No sx required.
49
Causes of claw diseases
Trauma
Neoplasia
Paronychia- inflamm of nail fold- bacteria/ fungi/ autoimmune (pemphigus foliaceus)
Symmetrical lupoid onychodystrophy
50
What is symmetrical lupoid onychodystrophy?
Not uncommon dz of dogs. Sloughing of nails, replaced by brittle, cracked, short claws. Histologically- interface dermatitis at junction of clawbed and underlying dermis. Amputation of P3 needed for histopathology. Trial rx (oxytetracycline/ nicotinamide)
51
Ddx of pustular dz in dogs
```
Pyoderma
Pemphigus foliaceus
Drug eruption
Juvenile cellulitis
Sub corneal pustular dermatosis
Sterile eosinophilic pustulosis
```
52
How do you approach pustular diseases in dogs?
Cytological examination of pustule contents
If consistent w/ pyoderma, tx w/ abx and re-examine after 10-20 days. Take skin scrapings to excl demodex as cause of pyoderma
If no response to abx or cytology not consistent w/ pyoderma then culture for bacteria, obtain skin bx
53
How do you approach pustular dz in cats and horses?
Bx in all cases as is unusual
54
Causes of ulceration
Self trauma
| Dz that involve epidermis or dermo-epidermal junction incl infections, autoimmune dz, drug reactions, neoplasia
55
Ddx for vesicles
Viral infection, irritant chemicals and burns, autoimmune or immune mediated dz
56
What is subepidermal vesicular autoimmune dz?
Immune attack against protein located in basement membrane, leading to loss of cohesion between the epidermis and dermis, frequently associated w/ accumulations of inflammatory cells e.g. neutrophils, eosinophils. Often seen around mucocutaneous junctions- axillae, groin, may involve MMs.
57
Examples of supepidermal dermatitides
Bullous pemphigoid
MM pemphigoid
Epidermolysis bullosa acquisita
58
What is intraepidermal vesicular dermatitis?
Autoantibody to desmosomal adhesion molecules in epidermis leads to separation of keratinocytes from each other and blister or pustule formation.
59
Examples of intraepidermal vesicular dermatitis
Pemphigus vulgaris- v rare, oral cavity affected in 90%, affects mucocutaneous junctions, ears, claws, axilla, groin. 2ry bacterial infection common.
60
What is pemphigus foliaceus?
Intraepidermal pustular dz
Transient pustules. Crusts, scales, alopecia, erosions, epidermal collarettes which affect the face, feet incl footpads, groin. Tends to become generalised. Fever, depression if severe.
61
How is pemphigus foliaceus diagnosed?
Hx. Clinical signs- crusting on face and feet. Bx. Pustule smears- acantholytic cells and neutrophils in the absence of bacteria
62
What is interface dermatitis?
The dermo-epidermal junction is obscured by inflammatory cells or hydropic degeneration
63
Examples of interface dermatitis
Discoid lupus erythematosus (nasal cutaneous lupus)
| Erythema multiforme/ toxic epidermal necrolysis
64
What is discoid lupus erythematosus?
Interface dermatitis
Depigmentation, scaling, erythema of nose extending to bridge of nose and sometimes affecting ears and periorbital areas
Tx- avoid sunlight, consider fluorinated GC e.g. 1-2% hydrocortisone. Alternative topical tx- tacrolimus. Combined tetracycline and niacinamide. Vit E.
65
What are the general tx options for autoimmune and immune-mediated dz?
Severe cases- high dose steroids (2-4mg/kg sid then maintain on eod; cats generally need double this), oral prednisolone, oral dexamethasone, azathioprine (not cats), chlorambucil
Mild cases- topical steroids, vitE, tetracycline/ niacinamide, low dose of oral steroids
66
What are the possible causes of skin dz in small furries?
```
Ectoparasites
Bacterial/ fungal/ viral
Neoplasia
Hormonal
Husbandary
Behaviour e.g. nesting
Nutrition
```
67
What ectoparasites occur in rabbits?
Cheyletiellosis- mildly to severely pruritic, dorsum, scaling, crusting, alopecia, erythema
Psoroptes- ear mite
68
What ectoparasiticides are used in rabbits?
Ivermectin
| Off license- selamectin, imidacloprid
69
What bacterial skin infections occur in rabbits?
Facial dermatitis/ dewlap- dental dz (pseudomonas)
Perineal- no coprophagia, urinary contamination
Facial abscesses- pasteurella multocida- dental dz, wounds
Pododermatitis (bumble foot)- s.aureus- obesity, caging
70
What abx are used for bacterial skin infections in rabbits?
B-lactams contraindicated
Careful of natural gut flora
Baytril- enrofloxacin licensed as oral or injectable
71
How does dermatophytosis present in rabbits and how is it treated?
Scaling, round areas of alopecia, broken off hairs, erythema, crusting, pruritus. Typically starting on dorsal nose, ears, paws. ZOONOTIC
Tx- enilconazole dip twice weekly (licensed for dogs), itraconazole orally (licensed for cats)
72
How does myxomatosis present?
Leporipox virus transmitted by fleas. Acute, fatal dz. Swollen mucosae
Less virulent strains and vaccinated animals- nodules, erythematous plaques +/- ulceration.
73
How is myxomatosis treated?
Supportive rx. No tx for virulent strains. Flea prophylaxis- imidacloprid licensed but not repellent.
74
How does rabbit myasis present and how is it treated?
Fly eggs around perineum--> maggots. Weak, old, obese animals w/ dirty perineum are predisposed.
Tx- clip, clean and flush area. Fluids, ivermectin, abx, analgesia. Fly control and cyromazine.
75
What ectoparasites affect guinea pigs?
Chewing lice
Fur mites
Burrowing mites- trixicarus caviae
76
How is trixacarus caviae treated?
Ivermectin injection
Selamectin spot on
Vit C
77
What endocrinopathy occurs in guinea pigs and how does it present?
Ovarian cysts
| Non-inflammatory bilateral symmetrical alopecia. Typically starting in flanks.
78
What important point should be remembered regarding guinea pig husbandry?
Require dietary vitamin C.
| All animals w/ skin dz should receive 50-100mg Vit C per day
79
What are the ddx for bald-old-hamster syndrome?
```
Demodecosis
Epitheliotropic lymphoma
Hyperadrenocorticism
Dermatophytosis
Nutrition
Trauma/ bedding/ abrasions
```
80
How is bald-old-hamster syndrome diagnosed and treated?
```
Hx- PD- cushings?
Hair plucks- demodex
Cytology- bacterial infection, lymphoma
Bx- lymphoma
Tx- none licensed, except baytril (2ry infections), ivermectin PO, amitraz
```
81
What are the notable physical characteristics of ferret skin?
```
Cerumen in ears
Comedones on tail
Active scent glands
Greasy coat, typical odour
Alopecia during breeding season
```
82
What ectoparasites occur in ferrets?
```
Ctenocephalides felis felis- tx all in contacts and environment, fipronil, advantage, selamectin ivermectin inj
Otodectes cynotis (ear mites)- excessive cerumen production and pruritus
```
83
What causes symmetrical alopecia in ferrets?
Breeding season
Oestrus associated alopecia- should be mated
Adrenal gland dz
84
What are the predisposing factors for canine otitis?
Conformation, obstruction, excessive moisture/ cerumen/ hair, cornification disorders, immunosuppression
85
What are the primary factors of canine otitis?
FB
Parasites
Hypersensitivity dz (AD, food), Contact dermatitis
Immune mediated dz
86
What are the secondary factors of canine otitis?
Bacterial infection- s.pseudintermedius, pseudomonas, proteus, klebsiella, e.coli
Yeasts- malasezzia
87
What are the perpetuating factors of canine otitis?
Structural and functional changes which prevent resolution of otitis.
Stenosis of lumen, middle ear dz.
88
What are the management aims for canine otitis?
Reverse perpetuating changes.
| Resolve 2ry factors. Address 1ry factors
89
What causes recurrent/ chronic pruritic otitis externa?
Allergic skin dz w/ 2ry bacterial, yeast or mixed overgrowth/ infection. Bilateral but not always concurrently or equally severe
90
What causes chronic progressive purulent otitis?
Long standing unresolved microbial infection, multi-factorial. Soft tissue changes and/or otitis media.
91
What are the characteristics of otitis media?
invariably accompanied by otitis externa- acute otitis externa, chronic/ recurrent otitis externa. Tympanum often intact. Signs relate to OE, neuro signs unusual.
92
What causes a transition from acute to chronic otitis?
Microbial shift from G+ve and malasezzia to G-ves.
| Multiple partially effective/ ineffective tx attempts leads to antimicrobial resistance.
93
When is surgery indicated in otitis?
When polyps/ tumours present. With irreversible stenosis. Aggressive medical tx failed, not possible or not wanted.
94
What are the common causes for tx failure in otitis?
Tx not long enough, inadequate ear cleaning, failure to identify and tx OM and soft tissue changes, failure to identify and control primary cause.
95
What is an aural haematoma?
Collection of blood within cartilage of ear, due to damage to branches of auricular a. Formed most likely due to trauma. Head shaking and ear scratching predispose. Likely causes incl parasite, FB, aural inflammation, allergy.
96
How can an aural haematoma lead to a contraction deformity?
Haematoma--> seroma--> fibrosis--> contraction deformity
97
What are the tx aims for an aural haematoma?
Address underlying source of inflammation. Evacuate haematoma. Prevent recurrence- pressure bandage, aspiration drain, sx
98
What are the conservative management options for an aural haematoma?
Needle aspiration- high recurrence
Pressure bandage
Continuous drainage through canula, penrose or closed suction drain for 2-3wks.
99
What are the surgical management options for an aural haematoma?
Incise concave surface of pinna (linear, ovoid, S or X shaped). Evacuate haematoma and hold closed w/ vertical sutures- need enough sutures to make sure no cavity. Leave incision open for drainage. Apply light bandage for several days. Remove sutures at 10-14d
100
What are the indications for a pinnectomy?
```
Neoplasia- 1cm margins
Cold
Trauma
Solar injury
Vasculitis
```
101
What are the aims of a lateral wall resection and when is it indicated?
Decrease temperature, humidity and moisture. Increase drainage and ventilation
Indicated for otitis externa which has not responded despite appropriate medical therapy
102
When is a lateral wall resection contraindicated?
Chronic endstage otitis externa
Irreversible horizontal canal dz/ stenosis
Otitis media
103
How is a lateral wall resection performed?
Make two vertical skin incisions from tragic notches ventrally. Join a ventral aspect and flap skin dorsally. Incise cartilage of lateral ear canal in 2 parallel vertical cuts. Flap ventrally and remove excess cartilage to form a baffle plate. Suture cartilage to skin epithelium w/ fine interrupted sutures. Buster collar. Remove sutures at 10-14d.
104
What complications may occur w/ a lateral wall resection?
Recurrence- poor case selection, inadequate tx of dermatological condition, poor surgical technique.
Wound breakdown/ infection.
105
What are the indications for a vertical ear canal ablation?
Same as for lateral wall resection- OE which has not responded to medical tx. But also specifically indicated for neoplasia of medial wall of vertical canal.
106
How is a vertical ear canal ablation performed?
Cut around the external auditory meatus. Extend incisions ventrally. Bluntly dissect around vertical canal and excise approx 2cm above annular ligament. Cut remaining vertical canal cranially and caudally to level of annular ligament, producing 2 baffle plates. Suture. Close any remaining skin w/ simple interrupted sutures.
107
What is the aim of a TECA and LBO?
Complete removal of all external ear tissue except pinna and removal of infected tissue w/in middle ear- salvage
108
What are the indications for a TECA and LBO?
Chronic end stage OE w/ obstruction of horizontal and vertical canals, persistent otitis following LWR/ VCA, OE and non responsive OM, neoplasia of horizontal canal, para-aural abscess, severe ear canal trauma
109
What are the contraindications for TECA and LBO?
Ear dz which can be effectively treated w/ or w/out LWR/VCA
| Neoplasia which has extended outside the external ear canal and middle ear
110
How is a TECA and LBO performed?
Cut around external auditory meatus. Dissect around vertical and horizontal canals. Excise at level of tympanic membrane. Extend external auditory meatus opening in bulla ventrally. Flush middle ear and carefully remove epithelium lining middle ear. Close SC tissues and suture cartilage to skin w/ interrupted sutures.
111
What complications cans occur w/ a TECA and LBO?
```
Conductive deafness (rare)
Facial n paralysis, horners syndrome
Haemorrhage
Vestibular dz
Infection and wound breakdown
Fistula/ sinus formation
Avascular necrosis of skin of pinna
```
112
What causes otitis media in dogs?
Usually by extension through tympanic membrane from otitis externa
Can rarely arise from haematogenous spread or from nasopharynx via eustachian tube.
113
What causes otitis media in cats?
Rarely as a result of OE
Ascending viral infection from nasopharynx associated w/ episodes of URT dz often implicated in development of polyps which originate from lining of tympanic bulla or Eustachian tube
114
What are the tx options for otitis media?
Medical- myringotomy, flushing middle ear w/ saline and 3-6wk course of systemic abx
TECA/LBO- if OM present w/ significant external ear dz
VBO- recommended if OM w/out severe external ear dz e.g. aural polyps in cats.
115
What are the indications for a ventral bulla osteotomy
Aural polyps
Middle ear neoplasia (rare)
1ry OM (rare)
*In cats be sure to enter both compartments
116
What are the possible complications of a VBO?
Recurrence of dz, horners (esp cats), hypoglossal n damage, vestibular syndrome, infection and wound breakdown, facial nerve paralysis (reported but much less likely than TECA/LBO)
117
What are the main causes for malasezzia overgrowth in cats?
Devon rex and sphynx cats
Allergic dz
Internal disorders incl paraneoplastic alopecia.
118
How is sarcoptes diagnosed?
Skin scrapes
Serology
Pinnal-pedal reflex highly suggestive
Trial tx
119
What causes hyperpigmentation?
Chronic allergic dz
Malasezzia
Endocrine
Demodecosis
120
What causes hypopigmentation?
```
Nutritional
Hereditary
Autoimmune
Neoplastic
Idiopathic
```
121
What are the most common benign skin tumours in dogs?
```
Lipoma
Perianal adenoma
Sebaceous hyperplasia/ adenoma/ adenocarcinoma
Cutaneous histiocytoma
Basal cell tumour
```
122
What are the most common malignant skin tumours in dogs?
MCT
STS
Melanoma
SCC
123
What clinical signs result from histamine release from a MCT?
V+, GI ulceration--> melaena
124
What clinical signs result from heparin release from a MCT?
Local bruising, perioperative bleeding
125
What are the most common skin tumours of cats?
```
Fibrosarcoma
SCC
Basal cell tumours
MCT
Lymphoma
```
126
What are the 3 major forms of the eosinophilic granuloma complex?
Eosinophilic granuloma
Eosinophilic plaque
Eosinophilic ulcer
127
What are some causes of eosinophilic granuloma complex?
Allergic skin conditions e.g. atopic dermatitis, flea bite hypersensitivity, food allergy, cutaneous adverse reactions
128
What is an eosinophilic plaque?
Part of EGC. Pruritic, raised, ulcerated plaque-like lesion, found anywhere on body. Esp common on ventral abdomen. Allergic skin dz.
129
What is an eosinophilic ulcer?
Part of EGC. Distinct, well demarcated, unilateral/ bilateral ulcers occurring at philtrum of upper lip or adjacent to upper canine tooth. Part of allergic response. Chronic lesions should be bx- r/o neoplasia (SCC) and bacterial/ fungal infections
130
What is an eosinophilic granuloma?
Part of EGC.
131
What are the tx options for EGC?
Where possible manage underlying cause. Glucocorticoids- inj, orally or topically. EFAs. Ciclosporin. Chlorambucil may be used in addition to steroids.
132
What is miliary dermatitis?
An important presentation of feline allergic skin dz. Focal areas of crusting (often h+), some papules, alopecia in advanced cases. Typically on dorsum.
133
How are mycoses diagnosed?
Microscopy- KOH/ paraffin oil, hairpluck/ skin scrape
Culture- Saboraud's medium
Histopathology- Gogott (silver stain) or PAS
Serology
134
What abx choice is appropriate for superficial pyoderma?
Cefalexine
| Co-Amoxyclav
135
What abx choice is appropriate for deep pyoderma?
Should always be based on C+S.
| Use cytology whilst awaiting results- cocci- cefalexine, rods- FQs
136
What topical antimicrobial agents are available?
Chlorhexidine
Benzoyl peroxide
Fusidic acid
137
What are the 3 main ways in which fungi cause disease?
Mycoses- invading and growing in tissues
Mycotoxicosis- producing toxigenic substances which when ingested cause dz
Allergy- hypersensitivity to fungal Ag
138
What are the characteristics of cryptococcus?
Spherical yeast budding on a narrow base. Main infection route is respiratory from pigeon droppings. May affect the respiratory, CNS or systemic system. Tip of the nose is the most common site in cats.
139
What are the characteristics of candidosis?
Less common. Normally an endogenous mycosis but occasionally exogenous infections may arise. Reproducing by budding on a narrow base.
140
What are the characteristics of malassezia pachydermatis?
Found on skin and mucosal sites in healthy dogs. Frequently present in large amounts in the ears of dogs w/ OE- significance uncertain. Reproduced by budding on a broad base
141
What is the main source of aspergillus?
Rotting plant and animal material- hay, straw and grain
142
What are the characteristics of aspergillosis?
Non-contagious, mainly respiratory mycosis. Infection of the posterior nasal turbinates by A.fumigatus is being increasingly recognised, Causes necrosis an erosion of turbinate bones and also affects epithelium, submucosa, BVs.
143
How is canine nasal aspergillosis diagnosed?
Microscopy of nasal washings- fragments of hyphae and spores. However, as such as common mould, dx also requires clinical signs, radiography and serology.
144
What is dermatophytosis?
Aka ringworm. Infection of the hair, nail or stratum corneum by fungus of the genera microspora, trichophyton or epidermophyton. Adapted to digest keratinous debris.
145
What are the most common dermatophyte species of importance in the UK?
Microsporum canis- 90% feline infections, 60% dogs
| Trichophyton mentagrophytes- 30% canine cases.
146
What is the pathogenesis of dermatophytosis?
M.canis most commonly from infected cats, T.mentagrophytes most commonly from wild rodents. Skin ivasion by adherence of arthrospores to stratum corneum cells. Spores germinate and hyphae invade SC aided by production of keratinases. Most then penetrate hair shafts. Induces an inflammatory response. Resolution w/in 1-3m. Chronic dz when organism fails to induce or has ability to suppress these responses or when host immunity compromised.
147
What are the clinical signs of dermatophyte infections in dogs?
Highly variable. Localised dz most common. Focal area of alopecia and scaling which expands peripherally and heals centrally. NB bacterial infection far more common. Or localised/ generalised furunculosis/ folliculitis/ scaling Or onychomycosis +/- paronychia.
148
What are the clinical signs of dermatophyte infections in cats?
Most commonly irregular, patchy alopecia +/- scaling.
149
How is dermatophytosis diagnosed?
Direct microscopy- KOH or liquid paraffin on skin scrapings/ hair plucks- fungal spores or hyphae
Fluorescence microscopy- UV microsope
Woods lamp- M cani fluoresce apple-green (however, 50% m.canis and all of trichophyton don't fluoresce.
Culture- skin scrapings and hair plucks inoculated onto Sabourauds dextrose agar for 2-4wks
Bx- fungal hyphae invasion
150
What is the tx for dermatophytosis?
Clip hair around lesion.
Systemic antifungal rx- griseofulvin- no longer licensed, itraconazole licensed for cats
Topical rx- alone unlikely to shorten course of dz as doesn't penetrate infected hairs. But assists in removal of surface organisms and reduces environmental contamination- malaseb- miconazole and chlorhexidine shampoo.
Monitor w/ repeat cultures
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What are the clinical signs of malassezia dermatitis?
Can complicate or mimic allergic skin dz. Often highly pruritic and refractory to previous tx w/ steroids, abx and parasiticidal agents.
Erythema, greasy exudate, hyperpigmentation and lichenification in chronic cases. Concurrent erythematous OE w/ variable ceruminous discharge.
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How is malassezia dermatitis diagnosed?
By elevated M.pachydermatis populations on lesional skin, good clinical and mycological response to appropriate antifungals
Tape strips, direct smears, cultures
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What is the tx for malassezia dermatitis?
2% miconazole/ 2% chlorhexidine (Malaseb) shampoo- q3d for 3 wks- antiyeast, antibacterial and good degreaser. Others (less effective)- selenium sulphide, ketoconazole, chlorhexidine shampoo
Enilconazole can be used as a rinse after selenium baths or applied to area as sole tx.
Systemic rx w/ ketoconazole or itraconazole v effective but more expensive.
