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Dermatology > Parasitic Skin Disease > Flashcards

Parasitic Skin Disease Flashcards

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Dermatology Board Prep flashcards
1
Q

What is the most common cause of pruritis? Is this good?

A

Ectoparasites

  • common
  • easy to treat
  • always investigate first
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2
Q

Why are ectoparasites important other than pruritic disease?

A

may be vectors of/contributors to other infectious diseases

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3
Q

Do parasites presence always indicate disease?

A

No
1. parasite always casues disease
2. some parasites sit on carriers or cause minimal disease BUT parasite may ellicit hypersensitivty
> reaction differs between individuals
3. commensal parasite rarely causes disease

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4
Q

Which parasites ALWAYS cause diseas?

A

Sarcoptes (mange mites -> scabies)

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5
Q

Which parasites are commensal and always present in the coat?

A

Demodex

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6
Q

Which species does demodex (arachnids) mainly affect?

A

Dogs (also cats and horses possible)

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7
Q

Which species does sarcoptes (arachnids) mainly affect?

A

Dogs only

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8
Q

Which species does cheyletiella (arachnids) mainly affect?

A

Dogs (also cats possible)

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9
Q

Which species does trombiculiasis (arachnids) mainly affect?

A

Dogs, cats and horses

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10
Q

Which species can get FAD?

A

Cats and dogs

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11
Q

Does trombiculiasis always need treatment?

A

No - only if bothering the dog

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12
Q

When is trombiculiasis season?

A

Strictly seasonal - autumn!
July -> sept/oct
> regional too

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13
Q

Is trombiluliasis a commensal?

A

No picked up from environment

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14
Q

Clinical signs of trombiculiasis

A
  • larvae just visable

- may be asymptomatic or severely pruritic

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15
Q

Tx of trombiculiasis?

A
  • none repellant, none licensed

- fipronil

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16
Q

What causes walking dandruff and scale?

A

Cheyletiella (blakei/yasurgi/parasitivorax)

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17
Q

How may cheyletiella mites be identified?

A 
> hair plucks
> coat brushing
> tape 
- palps
- eggs attached to hair shaft (nits)
18
Q

Which animals are affected by cheyletiella?

A

Cats, dogs, rabbits

19
Q

Why is cheyletiella a difficult problem?

A
  • survive in environment and on fomites 6 weeks

- zoonotic (will bite people though not establish on them)

20
Q

Clinical signs of cheyletiella

A
  • walking dandruff
  • pruritis may be v. mild or severe
  • primarily dorsal trunk
  • cats: miliary dermatitis
21
Q

Tx of cheyletiella?

A 
> suprisingly difficult (> 6 weeks)
> none licensed
- amitraz (dog)
- fipronil (dog and cat)
- selamectin (dog and cat) 
- moxidectin (dog and cat) 
- ivermectin (cat and rabbit) 
- selenium sulphide shampoo (dog and cat)
> clean environment
> treat all in contact dogs, cats, rabbits
22
Q

What is demodecosis?

A
  • inflammatory parasitic skin disease characterised by ^ no. demodex
23
Q

Which animals most commonly affected by demodecosis?

A
  • dog (d. canis, d. injai; short-bodied mites live in statum corneum rare)
  • uncommon in cat (d. cati, d. gatoi)
  • very rare in the horse
24
Q

Clinical signs of demodecosis?

A
  • prominant hair follicles and comedons
  • potential alopecia
  • demodex live on hair shaft head down in follicle (cigar shaped)
  • not necessarily itchy (no self trauma) but can be
25
Q

Potential manifestations of canine demidecosis?

A 
> juvenile onset, localised (~4mo)
- often recovers spontaneously
- inherited from bitch while suckling 
- cosmetic problem only
> juvenile onset, generalised (~4 mo)
- inherited predisposition
- does not recover spontaneously
> adult onset (local or generalised)
- true >2yo 
- suspect underlying immunosuppression eg. glucocorticoids, endocrinopathy, neoplasia 
(2* infection can -> deep pyoderma)
26
Q

Tx of demodecosis

A
  • min 12 weeks tx: tell client this!
  • monitor by PE and repeat scrapes/plucks
  • avoid steroids!!!
27
Q

Which breeds are commonly affected by demidecosis?

A
  • staffies

- great danes

28
Q

Which species most commonly affected by sarcoptic mange mites?

A
  • common in dogs
  • rarer in cats (usually asociated with affected dog)
  • notifiable in horses!!
29
Q

Which pathogen causes scabies?

A

Sarcoptes Scaibie

30
Q

How does sarcoptes behave on the skin?

A

Buries into epidermis -> crusted papules

31
Q

how can sarcoptes be found/diagnosed?

A

With difficulty!!

  • skin scrape to find mite, eggs or feaces, will rarely find tunnel (in stratum corneum) full of eggs, baby mites and feaces
  • may not easily find it
  • only few mites needed for intensely pruritic reaction
32
Q

Where does FAD cause pruritis?

A
  • Dorsal lumbosacral area
  • can be ventral abdo too
    > caudal body generally
33
Q

What mechanisms of FAD hypersesntitivty are possible? What effect may this have on testing?

A 
> multiple
- IgE mast cell mediated
- delayed cell mediated (basophil hypersense, TH1 macrophage, TH2 lymphocyte/eosinophil) 
> against various antigens
- saliva
- cuticle
- excreted metabolites/enzymes/toxins 
- feaces
34
Q

What is the main allergen associated with FAD?

A

Saliva

35
Q

Do fleas usually cause irritation without FAD?

A

No (some scratching only due to them running around)

36
Q

Age of onset of FAD?

A

3-5 years

37
Q

Predispositions for FAD?

A
  • breed

- atopic derrmatitis

38
Q

Is FAD seasonal?

A

May be

  • seasonal parasites picked up in summer
  • flea infestations in home too!! so may be all year round
39
Q

Diagnosis and Clinical signs of FAD?

A
  • small crusted papules surrounding bites
  • coat brushing: flea feaces
    > wet paper towel test
    > microscopic analysis
    FAD generally diagnosed after disease
  • need to show no signs with no medications
  • challenge test? No longer as spread blood diseases but worked well!
40
Q

What 2 types of allergy testing is available for FAD?

A

> intradermal testing (whole body extract)
- immediate and delayed reactions
- low sensitivity, high specificity
- may have false - as diluted saliva
- but may be false + due to environmental challenge
FceR1a based flea saliva specific serology
- better sensitivity and medium specificity (50%)
but doesn’t really change tx and flea control

41
Q

Management of FAD

A
  • TRY to control or avoid fleas (difficult esp. if going into other peoples houses etc. and even if treated as flea will start feeding within minutes of attaching)
  • If cannot be avoided: antipruritic/anti-inflammatory medication (GCs, antihistamines, EFA)
  • allergen-specific immunotherapy (whole flea extract ineffective, salivary ag promising but not available!)

Dermatology (25 decks)

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