Dermatology practical Flashcards
Describe these lesions
Patchy alopecia (fleece loss)
Dirty fleece - due to scratching
Erythematous skin
Serous exudation & crusting
Excoriation due to self inflicted trauma
What could cause these lesions and how would you test for them?
Psoroptes ovis (sheep scab) – Test: Superficial skin scrapings, Serum ELISA
Biting lice (Bovicola ovis) – Test: Direct examination
Dermatophilosis (‘lumpy wool’) (Dermatophilus congolensis) – Test: Impression smear cytology
Cutaneous myiasis – Test: Direct examination
Ticks – Test: Direct examination
What parasite is this?
Psoroptes ovis - surface mite – causing ‘sheep scab
How can Psoroptes ovis be treated?
Organophosphate dip, e.g. Diazinon
Macrocyclic lactone injections, e.g. ivermectin, doramectin, moxidectin
Describe these lesions
Multifocal patchy alopecia, affecting right caudolateral trunk and right hindquarters. Lesions mildly erythematous; variably delineated
What parasite is this?
Demodicosis (Demodex canis)
What advice would you give an owner of a dog with Demodicosis (Demodex canis)
D canis is normal inhabitant of canine skin which causes disease in immunocompromised animals –> advise investigate patient’s underlying health
How do you treat Demodicosis (Demodex canis)?
Isoxazoline course most effective (afoxolaner, fluralaner, sarolaner – all licensed)
Monitor with monthly skin scrapings - look at live v dead, life stages
Treat until 2 consecutive negative sets of scrapes
Incapable of living off host, so no need to treat environment
Multifocal crusting & diffuse scale affecting the lower limbs
Ill-defined swelling affecting lower limbs
8yo Fell pony mare is presented to you in December with lesions affecting all lower limbs.
Pony is stabled on straw at night, in barn with 3 others & turned out during day.
She is reported to be in good general health.
Lesions developed gradually over previous 4w. Scale seen initially, followed by crusting. Swelling developed in last week.
All ponies rub & nibble at their lower limbs & occasionally stamp.
What are your D/D and what tests will you do?
Involvement of multiple animals implicates contagious condition or one associated with environment
Chorioptic mange (Chorioptes equi infestation) - Superficial skin scraping
Dermatophilosis (‘mud fever’) Dermatophilus congolensis infection - stained impression smear cytology of underside of crust
Bacterial folliculitis (usually staphylococci) – secondary to primary cause - stained impression smear cytology of underside of crust
What is your diagnosis? (found on horse leg)
Ectoparasite = Chorioptes equi –> chorioptic mange
What is your diagnosis? (found on horse leg)
Filamentous branching chains of G+ve cocci = Dermatophilus congolensis –> dermatophilosis
Likely secondary problem, organisms entering through abrasions from self trauma caused by mites. Exacerbated by wet muddy conditions.
Superficial infection likely to have extended deeper to cause cellulitis
How do you treat Chorioptes in horses?
Full body clip
Doramectin injections (unlicensed for horse)
Turn out 24/7 to dry pasture
Stable disinfection
Label the cytology
11yo MN DSH cat presented with 5cm well-defined swelling on side of its neck that hasn’t been noticed previously. Cat is systemically well.
FNA of mass is taken.
What is your diagnosis?
How would you manage this?
Consistent with septic inflammatory (pyogranulomatous) exudate –> abscess (looks too well-demarcated clinically to involve significant cellulitis)
Treat:
- Lance (once matured), drain, flush
- NSAIDs
- Systemic antibiotic (e.g. amoxicillin-clavulanate 7 days) if systemically unwell/pyrexic
What parasite is this?
Sarcoptes
How do you treat dogs for Sarcoptes?
Isoxazoline
Physical cleaning of environment
Spray home with flea spray
Label the cytology sample from ear canal of dog with otitis
What parasite is this and how do you treat it in pigs?
Haematopinus (sucking louse)
Treat with Ivermectin and clean environment
Label the cytology sample from ear canal of dog with otitis. What is your diagnosis?
How do you treat a dog with a Malassezia ear infection?
Polypharmacy ear-drop containing anti-fungal agent
Pre-treat with ear cleaner with antimicrobial/antibiofilm action (e.g. TrizEDTA/chlorhexidine product)
If recurrent, investigate underlying cause
What parasite is this and what advice would you give to owner of a dog with it?
Ixodes tick
Treat dog to kill remaining undetected ticks (e.g. isoxazolines for rapid kill)
+- Product with tick-repellant activity (e.g. pyrethroids) to try to prevent further infestation
Avoid ‘tick areas’ where possible, esp spring/autumn
Check dog after every walk to remove tick manually as fast as possible (some diseases not transmitted for first 48h after bite)
What parasites can you detect with coat brushing?
Superficial parasites, esp fleas, Cheyletiella or lice
What parasites can you detect with unstained acetate tape strip?
Surface mites (e.g. Cheyletiella) & lice
What parasites can you detect with superficial skin scrapings?
Surface parasites
eg Cheyletiella, Neotrobicula autumnalis, Otodectes
What parasites can you detect with deep skin scrapings?
into epidermis forparasites burrowing in epidermis, e.g. Sarcoptes
until blood oozes for Demodex (deep in follicles)
What parasite is this? (superficial skin scrape)
Cheyletiella
What parasite is this? (superficial skin scrape)
Neotrombicula
What parasite is this? (deep skin scrape)
Sarcoptes
What parasite is this? (deep skin scrape)
Demodex canis
What tests can be used to detect demodicosis?
Deep skin scrape
Hair pluck
Biopsy
What stage is this hair bulb in?
Telogen bulb
- spear-shaped
- rough
- no pigment
Inactive hairs
Normally 80-90%
often 100% in endocrinopathies
What stage is this hair bulb in?
Anagen bulb
- rounded
- smooth
- pigmented centre +/-
- bulb may fold around shaft when plucked
Actively growing hairs
Normally 10-20%
What condition does this dog have?
Dermatophytosis
What condition does this dog have?
Colour dilution alopecia
- Progressive alopecia of dogs with dilute coat colours
- Clumps of melanin seen on trichogram –> weaken hair –> fracture of shaft –> alopecia
What can you see here and what conditions can cause it?
Follicular casts
- ‘collars’ of keratin around shaft
- Seen in diseases with increased keratin produced in hair follicle
e.g.
- Sebaceous adenitis
- Demodicosis
- Dermatophytosis
- Endocrinopathies
- Vitamin-A associated dermatosis
What can you see here and what does it indicate?
Angular broken ends
Indicates self-inflicted hair loss & probable pruritus
When do we use Wood’s lamp examination?
In any patient in which ringworm is suspected (including inflammatory & non-inflammatory alopecias)
For what lesions are direct impression smears useful?
Moist exudative & ulcerated lesions in accessible areas
What areas can we sample with cotton bud swabs?
Ear canal cytology
Drier skin surface, esp if inaccessible for direct impression smear
For what lesions are acetate tape strip (stained) useful?
or dry or scaly skin
To sample in folds (eg interdigital area)
What samples can be collected to visualise cells/microbes below skin surface?
FNA for cytology
Tissue biopsy for histopathology
When do we use skin surface swabs for bacterial culture and what do we sample?
When to use?
- To know precise identity of bacterium or antibiotic susceptibility pattern
What to sample?
- exudate from ears
- contents of fresh pustule/bulla – burst with sterile needle or aspirate
- skin under margin of epidermal collarette or under crust
- surface microorganisms, if appropriate
Send to laboratory in transport medium
When do we use a dermatophyte culture?
In any patient with suspected dermatophyte infection
When do we use a tissue culture?
For infection below skin surface (e.g. deep pyoderma)
