Clinical signs of and approach to pruritus Flashcards Preview

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Flashcards in Clinical signs of and approach to pruritus Deck (22)
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1
Q

What is pruritus?

A

‘Unpleasant sensation that elicits the desire or reflex to scratch (rub, lick, chew)’

Classify as

Pruriceptive pruritus – due to stimulation of peripheral receptors in skin (in presence of healthy nervous system). Usually due to skin disease

Neuropathic pruritus – generated in CNS in response to

  • circulating pruritogens (eg cholestasis)
  • pharmacological mediators (eg intraspinal morphine)
  • anatomical lesion of PNS or CNS, eg syringomyelia in CKCS
2
Q

How important is pruritus?

A

Pruritus is a physiological self-protective mechanism, designed to remove the agent causing the sensation from the skin (eg parasite, biting insect)

But enormous consequences if inciting agent is not promptly removed…

3
Q

How do dogs show they have pruritis?

A
  • Scratch
  • Rub
  • Nibble (may see hair at base of incisors/canines)
  • Lick – often not perceived as pruritus by owners
  • Temperament changes
4
Q

How do cats show pruritis?

A
  • Often secretive and not noticed by owners
  • May see
    • Overgrooming
    • Hair plucking
      • Vomit hairballs
      • Tufts of hair round house
      • Hair in faeces
5
Q

How do horses show pruritis?

A
  • Rub
  • Stamp
  • Biting
  • Scratch
  • Buck/kick
  • Temperament changes
6
Q

What are the causes of pruritis?

A
7
Q

Why is the signficance of microbial disease so important in treating pruritis?

A
  • Malassezia dermatitis and bacterial pyoderma cause pruritus VERY commonly but are almost always secondary to an underlying cause.
  • Need to identify and treat the infection, but also establish the underlying cause.
  • To investigate underlying cause, it is important to clear these secondary infections WITHOUT USE OF CORTICOSTEROIDS and assess residual pruritus.
    • If pruritus resolves fully: consider underlying immunosuppressive disease, including endocrinopathies
    • If pruritus remains: consider esp allergies (and parasites if not controlled)
8
Q

Draw a schematic that shows approach to dermatitis cases?

A
9
Q

Discuss how age can inform signlament?

A
  • Consider not only age now, but age of ONSET of first signs of pruritus (often v minor)
    • important – many cases will have started several years ago!
  • Most parasites can be present at any age (except Demodex usually old/young animals)
  • Atopy usually 6mo-3yo onset
  • CAFR onset any age
  • Older animals with no prior skin disease consider
    • neoplasia
    • microbial infection, secondary to immunosuppression/ endocrinopathy
10
Q

Outline some breed dispositions to pruritic conditions?

A

Staffordshire bull terrier – demodicosis, atopic dermatitis

Labrador retriever – atopic dermatitis

Bassett hound – Malassezia dermatitis

11
Q

What is the ‘typical’ presentation of Atopic dermatitis (environmental atopy)?

A
  • Age onset <3yo (usually >6mo)
  • Dog lives mostly indoors
  • Involvement of feet +/or pinnae
  • Frequent involvement of ventrum, face, otitis externa
  • Ear-margins/dorsal lumbosacral area unaffected
  • History of recurrent bacterial and/or Malassezia infections
  • Glucocorticoid-responsive pruritus
  • No contagion
12
Q

What is the ‘typical’ presentation of Cutaneous adverse food reaction (food-induced atopy)?

A
  • Any age of onset
  • Involvement of feet +/or pinnae
  • Frequent involvement of face, ventrum, otitis externa
  • Ear-margins/dorsal lumbosacral area unaffected
  • History of recurrent bacterial and/or Malassezia infections
  • +/- Glucocorticoid-responsive pruritus
  • No contagion
  • +/- tendency to GI disturbance, more frequent defaecation
  • (NB often clinically indistinguishable from environmental atopy)
13
Q

What is the ‘typical’ presentation of Sarcoptic mange?

A
  • Any age of onset
  • Increased risk if fox contact
  • Pruritus, papules, crusts affecting especially (but not exclusively) pinnal margins, hocks, lateral elbows, ventrum
  • Potential contagion/zoonosis
14
Q

What is the ‘typical’ presentation of Canine FAD?

A
  • Esp caudal/dorsal pruritus
  • Potential contagion/zoonosis
  • NB not all infested animals itch!
  • (NB head/face/ventrum also frequently affected in cats)
15
Q

What is the ‘typical’ presentation of Neotrombicula autumnalis (Harvest mites)?

A
  • Seasonal history (June-Sept)
  • Often feet (NB interdigital skin!), head
16
Q

What are your main differential diagnoses?

Scenario A:

  • 18 month old NM Shar-pei
  • Good general health
  • Alopecia and pruritus for past 6 months affecting limbs, ventral neck
  • Bilateral otitis
A
  • Environmental atopy (allergic dermatitis)
  • Food induced atopy
  • pyoderma (secondary)
  • demodicosis
  • sarcoptes
  • fleas (on list but not high up because distribution weird) .
17
Q

What are your main differential diagnoses?

Scenario B:

9 year-old ME Shar-pei

No prior skin disease

Recent-onset alopecia and pruritus

Reluctant to exercise

A
  • Food induced atopy
  • sarcoptes
  • fleas
  • demodicosis (maybe more likely because older due to some elderly immune mediated disease)
  • endocrinopathy goes up list as older dog
18
Q

What are your main differential diagnoses?

Scenario C:

5-month old ME Shar-pei

Alopecia and pruritus from 3 months of age

A

Demodicosis goes to top of list as younger dog

19
Q

What are the most likely d/dx for this case:

  • Case 1 Ellie
  • 2yo NF EB Terrier
  • Chewn feet from 9 months old
  • Intermittent bilateral otitis externa
  • Recent erythema and pruritus of inguinum
A

D/dx list

  • Environmental Atopy
  • Food induced atopy
  • Mallasezia, dermatitis and pyoderma
  • Demodicosis

Result:

This is a dog with environmental atopy with secondary mallassesia and bacterial pyoderma.

20
Q

What are the most likley d/dx for this case:

Case 3 Bobby

9mo JRT ME

Generalised erythema and pruritus, esp affecting feet, ventrum, axillae, face since owned (8wk old)

No improvement with short course of corticosteroids

Mild temporary improvement with antibiotics

Other dog/owner unaffected

A

DDx

Demodex

21
Q

What are the take home messages for approach to pruritis cases?

A

Major causes of pruritus are

  • Parasites
  • Microbial infection
  • Hypersensitivities

For each case

  • Take a thorough history
  • Look carefully – do thorough clinical exam
  • Draw up d/d list
  • Eliminate parasites and microbial infections
  • Proceed to allergy/further investigations if needed

Effective communication essential to ensure client understanding and compliance..

22
Q
A

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