Crusting & scaling Flashcards
(33 cards)
1
Q
Conditions that cause crusting/scaling
A
- bacterial infection
- dermatophytosis
- pemphigus
- parasites
- chronic diseases
2
Q
Examples of bacterial infections that cause crusting/scaling
A
- dermatophilus congolensis
- staph/strep folliculitis
2
Q
Examples of parasites that cause crusting/scaling
A
- mites
- lice
- Onchocerca
3
Q
Examples of chronic diseases that cause crusting/scaling
A
- HS
- drug reactions
- photosensitisation
4
Q
Characteristics of rain scald
A
- Dermatophilosis (D. congolensis)
- Gram-positive facultative anaerobic actinomycete (railroad tracks)
- likely quiescent form in horse skin > skin damage and moisture
- zoospores > motile and flagellate form
- zoospores may remain viable in crust for up to 2 months
- it’s contagious with an incubation period of 2-15d depending on host immunity
5
Q
Predisposing factors for rain scald
A
- poor nutrition
- poor hygiene (sweaty horses)
- high temperature and humidity
- low immunity
6
Q
Rain scald lesions (description, location)
A
- primary lesions are tufted papules that often coalesce and become exudative > large oval lesions with a paintbrush effect > thick crust that leaves a thin pus on the dermal surface
- removal of lesions/crusts can be painful
- lesions can be annular and often follow a dribbling or scald line pattern particularly in the dorsum and trunk
- location: rump, saddle areas, face and neck and pastern coronet
6
Q
Rain scald general management and tx
A
- most cases spontaneously regress within 4w
- rarely transmitted horse to human but wear gloves
- wash tack: rug, saddle pads, brushes, etc 60C (50% Captan solution)
- keep horses dry after exercise
- maintain clean and dry bedding, avoid accumulation of manure
- avoid sunlight in affected areas as can aggravate irritation
7
Q
Rain scald local tx
A
- antiseptic washes: chlorhexidine or povidone-iodine based daily for 1w then once a week until resolution
- daily appliction of 5% K-permanganate for 5d
- dry with a towel or heat lamp
8
Q
Rain scald systemic tx
A
- in highly exudative and painful cases with/without secondary infections (staph/strep)
- penicillin for 3-5d (if pyrexic and/or anorexic)
- TMPS for 2w
9
Q
Dermatophytosis
A
= ringworm
- Trichophyton equinox [+++] and Mycrosporum gypseum
10
Q
What aged horse is more likely to be affected by ringworm?
A
- young
10
Q
Ringworm (primary lesions, location, clinical signs)
A
- primary lesions: erected hairs in circular areas, typically silvery and slightly scaly extending centripetally»_space; circular areas of alopecia
- location: head, neck, thorax and girth
- sometimes a component of mud fever
- erythema might be seen in white areas
- pruritus and mild pain are normally present in early colonisation: keratinsases
11
Q
Ringworm management
A
- rarely transmitted horse to human but still zoonotic so wear gloves, esp immunocompromised people and children
- correct nutritional imbalances or primary immunosuppressant disease
- strop training/riding and working animals until recovery
- separate affected from unaffected horses
- exposure to sunlight might be beneficial
- clean and disinfect tack with inorganic peroxide compounds
- if premises outbreak: K-monopersulphate on surfaces ‘fogging’
11
Q
Ringworm spread & pathogenesis
A
- normally spread through contaminated girths, boots, clippers, brushes, etc
- mechanical disruption of skin is necessary for fungal colonisation
- invasion of hair follicle is key on pathogenesis: keratinsases facilitate invasion of hair shafts
- fungus requires hair in anlagen (active keratin production) for proliferation, hairs in telogen limit the spread»_space; self-limiting infection
12
Q
Photosensitisation
A
= abnormal reaction of the skin when exposed to UV-radiation
12
Q
Ringworm local tx
A
- chlorhexidine 4% spray daily for 7d
- chlorhexidine 2% _ miconazole 2% spray or shampoo 2-3x weekly
- clotrimazole 1% + betamethasone 0.1% cream/lotion
- miconazole 2% spray/cream/lotion
- enilconazol 0.2% dip
- lime sulfur 5% dip
13
Q
Types of photosensitisation
A
I, II, III
14
Q
Type I photosensitisation
A
- ingestion of photodynamic agent: plants
- e.g. St Johns wort, Perennial rygrass
14
Q
Type II photosensitisation
A
congenital disease: abnormal metabolism of porphyrins
15
Q
Type III photosensitisation
A
- most common
- liver failure
- liver normally incorporates to bile chlorophyll degradation products (phylloerythrin and porphyrins)
- if not cleared into bile they reach the skin and act as photodynamic agents in white areas
16
Q
Photosensitisation (clinical signs, treatment/management)
A
- non-pruritic crust in white areas
- treat primary problem
- remove from pasture
- apply suncream (>50+)
- cover affected areas until healing
17
Q
Theoretical pemphigus antigens
A
- desmoglein protein
- environmental triggers: UV, Culicoides
- food ingredients
18
Q
Pemphigus
A
- exfoliative dermatitis due to a type II HS with antibodies directed epidermal cells
- no breed or sex predisposition
- wide range of ages in 1st diagnosis, normally young horses
19
Pemphigus diagnosis
biospy- acantholysis
20
Pemphigus foliaceous
- more scaling and severe diffuse crusting
20
Types of pemphigus
- foliaceous
- vulgaris/bullous
21
Pemphigus vulgaris/bullous
- mucocutaneous junctions with ulceration and bulla formation in the oral mucosa primarily
21
Pemphugus tx & management
- long-term glucocorticoids (preds or dexamethasone): immunosuppressive doses
- omega fatty acids
- vitamin E supplementation (5000IU/500kg)
- sunlight restriction
- address underlying triggering factors?
22
Onchocerca
- microfilaria parasite lowering prevalence due to the use of microcytic lactone dewormers (ivermectin/moxidectin)
- rarely see in UK
23
What exacerbates onchocerciasis and why?
- warm weather -> moving from deep dermis to superifical
- adults live in nuchal ligament
24
Onchocerca lesions (location, description)
- head, neck, ventral chest/abdomen, rarely ocular lesions
- alopecic flat crusts, mildly raise
25
Onchocerca tx
- microcytic lactones
- permanent leukoderma possible
