dermatology cases

Question 1

Describe the appearance of macrophages and lymphocytes on cytology

Answer 1

Question 2

Describe the anatomical features of insects

Answer 2

Question 3

Describe the differentiation between insects

Answer 3

Question 4

Describe the differentiation between lice

Answer 4

Question 5

Describe the anatomical features of arachnids

Answer 5

Question 6

Describe the differentiation between arachnids

Answer 6

Question 7

Describe the differentiation between ticks

Answer 7

Question 8

Describe the differentiation between mites

Answer 8

Question 9

Describe the differentiation between burrowing mites

Answer 9

Question 10

Give examples of different chewing lice and their host species

Answer 10

Question 11

Give examples of sucking lice and their host species

Answer 11

Question 12

How can psoroptes surface mites be differentiated from other surface mites?

Answer 12

Question 13

Give examples of surface mites and their host species

Answer 13

Question 14

Give examples of burrowing mites and their host species

Answer 14

Question 15

Label this cytology

Answer 15

Question 16

An 11yo MN DSH cat is presented with a 5cm well-defined swelling on the side of its neck that has not been noticed previously. The cat is systemically well

A fine needle aspirate of the mass is taken, cytology of which is shown

Describe the cytological findings and give a diagnosis.
How would you treat?

Answer 16

Cytology:
- Degenerate neutrophils ++++
- Macrophages ++
- Bacteria - rods +++ (some in clusters/chains), cocci/diplococci +
- some bacteria intracellular

Diagnosis - septic inflammatory (pyogranulomatous) exudate => abscess
- looks too well-demarcated clinically to involve significant cellulitis

Treatment:
- Lance (once matured), drain, flush
- NSAIDs
- Systemic antibiotic (e.g. amoxicillin-clavulanate 7 days) if systemically unwell/pyrexic

Question 17

You are asked to examine a fox which has been brought in by one of your clients as they have found it collapsed in their garden. The fox is dehydrated and very thin, with severe crusting skin lesions. You take a deep skin scraping to examine. The owner has 2 dogs.

Examine the ectoparasite found and identify the genus to which it belongs.
What treatment/advise would you give?

Answer 17

Sarcoptes:
- highly contagious to dogs
- zoonotic
- can survive up to 3 weeks in environment

Treat dogs prophylactically with isoxazoline or selamactin/moxidectin/imidacloprid spot ons
Physically clean environment
Spay home with ‘flea spray’ containing pyrethroid (adulticide)

Question 18

Label this cytology

Answer 18

Question 19

What can be seen in this cytological sample?

Answer 19

Keratinocytes (squames) in background/foreground
Bacteria ++++ (rods, cocci)

Question 20

A 5-year-old FN English Setter is presented with severe otitis affecting the left ear
Describe the cytological finding and how you will treat.

Answer 20

Cytology
Bacteria ++++ – mixture of cocci and rods
Neutrophils + with some nuclear streaming
Squames +

Advise:
- bacterial culture and sensitivity testing of rods (need to establish organism, esp if Pseudomonas)
Treat empirically with ear drops
Treat with glucocorticoids to reduce inflammation (topical and systemic at anti-inflammatory dose due to marked inflammation)

Question 21

To which genus does this ectoparasite belong?

Describe the lifecycle of this parasite and how you would treat it

Answer 21

Haematopinus:
- sucking louse
- feeds on blood

Life cycle on host:
eggs on hairs => 7-14 days => nymphs => 12 days => adults => 4 days => lay eggs

Treatment:
- Ivermectin
- Physical clean to environment.

Question 22

Label this cytology and give a diagnosis

Answer 22

Question 23

A 1-year-old FE Springer Spaniel is brought to your surgery due to otitis affecting the right ear
What is your inference from cytology of the ear canal
How would you treat it?

Answer 23

Cytology
Malassezia ++ Neutrophils ++, very degenerate; nuclear streaming ++
Some areas of biofilm (blue ’lacey’ appearance)

Treatment
- 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

Question 24

This parasite has been found on a dog
Identify the parasite to genus and state what advice you will give.

Answer 24

Inornate (no ornamentation), no festoons, anal groove anterior to anus => Ixodes sp.

Can transmit a range of diseases to various species, including Lyme disease to the dog

Ticks on dog of no direct risk to owner, as are contracted from ground, though owner could also become infected from same source as dog

Advise
- Treat dog(s) to kill any remaining undetected ticks (e.g. isoxazolines for rapid kill)
- Consider use of 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)

Question 25

Describe these lesions

Answer 25

Patchy alopecia (fleece loss) Dirty fleece - due to scratching Erythematous skin Serous exudation & crusting Excoriation due to self inflicted trauma

Question 26

A group of sheep have been seen rubbing, you find these lesions. What are the most likely differential diagnoses and how would you test for these?

Answer 26

Psoroptes ovis – ‘sheep scab’ - superficial skin scrapes, serum ELISA Biting lice (Bovicola ovis) - direct examination of crust Dermatophilosis - ‘lumpy-wool’ - Dermatophilus congolensis - impression spear cytology - if wet conditions Cutaneous myiasis - direct examination Ticks - direct examination - May cause intense irritation as they feed

Question 27

This parasite was found on some rubbing sheep. What is it? How would you treat?

Answer 27

Parasite is Psoroptes ovis - surface mite – causing ‘sheep scab' Organophosphate dip, e.g. Diazinon Macrocyclic lactone injections, e.g. ivermectin, doramectin, moxidectin

Question 28

Describe these lesions

Answer 28

Multifocal patchy alopecia, affecting right caudolateral trunk and right hindquarters. Lesions mildly erythematous; variably delineated

Question 29

These lesions have been found on an otherwise healthy dog. What are your top differential diagnoses and how would you test for these?

Answer 29

Bacterial folliculitis (superficial pyoderma) - would be secondary to underlying cause - stained acetate strip for cytology Dermatophytosis - Wood's lamp exam - trichogram - microscopy of scale from lesion periphery - McKenzie coat brushing, scale, lesion periphery hair plucks => dermatophyte culture Demodicosis - deep skin scraping - trichogram

Question 30

This parasite was found on a deep skin scrape of these lesions. What is your diagnosis and what advice will you give?

Answer 30

Diagnosis: Demodicosis (Demodex canis) Treatment - Isoxazoline - Incapable of living off host, so no need to treat environment - Monitor with monthly skin scrapings - Monitor with monthly skin scrapings

Question 31

how does demodex canis cause disease?

Answer 31

D canis is a normal inhabitant of canine skin which causes disease in immunocompromised animals - investigate animal's underlying health

Question 32

Describe the lesions

Answer 32

Multifocal crusting and diffuse scale affecting the lower limbs Ill-defined swelling affecting lower limbs

Question 33

Pony on straw at night with 3 others. Scale was seen initially, followed by crusting. The swelling has developed in the last week All ponies have been seen to rub and nibble at their lower limbs, and occasionally to stamp. what are your top differential diagnoses and how would you test for these?

Answer 33

Chorioptic mange - Chorioptes equi infestation - superficial skin scraps, coat brushing 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 Deep pyoderma/cellulitis – extension of initial superficial bacterial infection

Question 34

This parasite was found on a superficial skin scrape of some itchy ponies. These are the cytological results of skin under crust. What is your diagnosis and how has this situation developed? how would you treat?

Answer 34

Ectoparasite = Chorioptes equi => chorioptic mange – likely primary problem 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 Treat Chorioptes – Full body clip - Doramectin injections - Turn out 24/7 to dry pasture - Stable disinfection Treat microbial infection - Topical chlorhexidine washes - Systemic antibiotics (e.g. doxycycline) for cellulitis