Demodicosis (Marsella) Flashcards

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1
Q

Demodex canis Life Cycle

A
  • 25-30 days
  • Egg → larvae (6 legs) → Nymph (8 legs) → adult (8 legs)
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2
Q

Demodex transmission

A
  • Mites transmitted from bitch to pups
  • Present in low numbers in healthy, post-natal dogs
  • NOT contagious
  • NOT zoonotic
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3
Q

Demodex pathogenesis

A
  • Deficient cell-mediated immune response
  • Genetics (autosomal recessive)
  • Immunosuppression
  • Bacterial folliculitis (Staph is an immunosuppresant)
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4
Q

Common causes of immunosuppression in juveniles

A
  • Poor nutrition
  • Stress
  • Estrus
  • Endoparasites
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5
Q

Common causes of immunosuppression in adults

A
  • Steroids
  • Endocrinopathies
  • Neoplasia

(Demodicosis usually presents before the underlying disease does)

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6
Q

Clinical signs of demodicosis

A
  • Papules/pustules
  • Erythema
  • Scaling
  • Crusting
  • Comedones
  • Patchy alopecia
  • Hyperpigmentation
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7
Q

Differential diagnosis list for comedones

A
  • Demodex!!!
  • Endocrine disease
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8
Q

Demodicosis diagnosis

A
  • Deep skin scrapes
  • Hair plucks (negative does not R/O)
  • Biopsy (Shar peis, scar tissue, pododermatitis)
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9
Q

Onset of juvenile onset demodicosis

A
  • Small breed < 12 mos
  • Lrg breed < 18 mos
  • Giant breed < 24 mos
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10
Q

Onset of adult onset demodicosis

A
  • Small breed > 12 mos
  • Lrg breed > 18 mos
  • Giant breed > 24 mos
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11
Q

Juvenile onset localized demodicosis

A

Evidence of mites in one area based on 5 deep skin scrapes. Benign.

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12
Q

Questions to ask with deep skin scrape of demodex

A
  1. Is it generalized?
    • Scrape 5 places total
  2. If not, will it become generalized?
    • Don’t tx, wait and see
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13
Q

Prognosis for localized demodicosis

A
  • 90% will clear spontaneously in 6-12 wks
  • 10% will generalize
  • Prognosis good
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14
Q

Treatment for juvenile onset localized demodicosis

A
  • Benign neglect
  • Abx (esp. if pustular)
    • Topical 2% mupirocin, benzoyl peroxide gel/shampoo
    • Systemic
  • De-worming, HW prevention
  • Good diet
  • Supportive
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15
Q

Treatments to avoid in juvenile onset localized demodicosis

A
  • Steroids
  • Anti-mite therapy
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16
Q

Why not treat localized demodicosis w/ miticides?

A
  • To know if it will become generalized
  • Prevent unnecessary medical treatment
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17
Q

Localized demodicosis recheck

A
  • 2-4 wks later
  • Deep skin scrape in same 5 spots
    • mite counts decr: lesion resolving, recheck in 4 wks
    • mite counts incr. +/- other positive sites: may be progressing to generalized
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18
Q

Generalized demodicosis

A
  • 5 or more localized lesions
  • Involvement of an entire body region (ex. head)
  • Involves 2 or more feet (pododemidicosis)
19
Q

Cause of juvenile onset generalized demodicosis

A

Hereditary

20
Q

Juvenile onset generalized demodicosis prognosis

A
  • 50% self clear
  • 50% need anti-mite treatment
    • of those that need treatment, 5% need lifelong treatment
  • 97% clear w/ proper tx
21
Q

Adult onset generalized demodicosis

A
  • Age > 1-2 yrs
  • Differentiate from a juvenile onset case that was never cleared/diagnosed
  • Underlying immunosuppression
22
Q

Pododemodicosis

A
  • Generalized demodicosis
  • Involves 2+ feet
  • Often chronic and resistant to therapy
23
Q

Generalized demodicosis treatment

A
  • Treat underlying cause
  • Miticide
  • Abx (2º bacterial infections)
    • until 1st negative scrape
  • Benzoyl peroxide shampoo
    • Follicular flushing
24
Q

Amitraz (Mitiban)

A
  • Miticide dip
  • MAO inhibitor, alpha-2 agonist, inhibits prostaglandin
  • Clip hair short & bathe w/ benzoyl peroxide before dipping
  • Dip weekly until 3 negative scrapings 2-4 wks apart
25
Q

Amitraz (Mitiban) contraindications

A
  • Toy breeds (need to dilute more)
  • Cats
  • Sick, old patients
  • Extensive ulcerations
26
Q

Amitraz (Mitiban) adverse effects

A
  • Sedation/dull mentation
    • reversal agents available if too severe (yohimbine, atipamezole)
  • Owners w/
    • asthma
    • diabetes
    • taking MAO (Parkingson’s disease)
27
Q

Amitraz (Mitaban) failure

A
  • No improvment after 6-9 dips
  • Causes: steroids, untreated Staph pyoderma, concurrent dz, genetics, long hair, bath between dips, poor owner compliance, premature discontinuation
28
Q

Ivermectin (Ivomec)

A
  • Miticide (off label)
  • Amitraz resistant cases
  • Animals that do not tolerate dips
  • Build up to final dose slowly & watch for neuro signs
  • Treat until 3 consecutive negative scrapes
29
Q

Ivermectin contraindicaitons

A

White feet don’t treat

Collies, border collies, shelties, old english sheep dog, aussies

30
Q

MDR1 gene deletion

A
  • Defect in proton pump
  • Drug (ivermectin) crosses into brain, but is not pumped out efficiently
  • Incr. risk of neuro signs w/ ivermectin
  • Collies, border collies, shelties, old english sheep dogs, aussies
31
Q

Moxidectin (Advantage Multi)

A
  • Off label use
  • Weekly or every other week application
  • Systemic absorption
  • Less effective than oral ivermectin but possible option for dogs who can’t have ivermectin
32
Q

Bravecto (flurolaner)

A
  • 1 pill eliminated 100% of mites by day 56
  • More effective than monthly Advantage Multi
  • Safe for MDR1 breeds
33
Q

Generalized demodicosis monitoring

A
  • Deep skin scrape 5 sites (always include muzzle and 2 feet)
  • Record mite counts
  • Re-scrape same sites every 4 wks
  • Treat until 3 consecutive negative scrapes
34
Q

Factors effecting prognosis of generalized demodicosis

A
  • Breeds difficult to cure: old english sheep dog, Afghan hound, shih tzu, lhasa apso
  • Heat cycle can cause incr. in mite count (spay/neuter)
35
Q

When to spay/neuter w/ generalized demodicosis

A
  • pyoderma clears
  • before or at 1st skin scrape
  • don’t wait til they are completely clear because they will relapse and get worse after surgery
36
Q

Adult onset generalized prognosis

A

Depends on if you can find and control underlying cause

37
Q

Demodex cati

A
  • Follicular mite (long & skinny)
    • Deep skin scrape
  • Variable pruritis of head & neck
  • Immunosuppressed (generalized)
    • Diabetes, FeLV, FIV, metabolic dz
38
Q

Demodex gatoi

A
  • Stratum corneum mite
    • Superficial skin scrape
  • Contagious
  • Can be very pruritic
    • Trunk, head, neck
39
Q

Feline Demodicosis clinical features

A
  • Localized or generalized
  • Alopecia
  • Scaling
  • Erythema
  • Hyperpigmentation
  • Ceruminous otitis externa
  • +/- pruritis
40
Q

Feline demodecosis diagnosis

A
  • Broad superficial scrape for D. gatoi
    • Dorsal neck/lateral, antebrachium
  • Deep scrapes at 3-5 sites for D. cati
    • local vs. generalized
41
Q

Demodex cati treatment

A
  • Ivermectin
  • LymDip (lime sulfur dip)
  • Spontaneous resolution possible
42
Q

Demodex gatoi treatment

A
  • LymDip (lime sulfur dip)
    • Cone until dry to prevent oral ulcers & GI upset
  • Treat all cats in contact
43
Q

Feline demodicosis prognosis

A
  • D. gatoi
    • excellent w/ tx
  • D. cati
    • poor if unable to find underlying cause
    • good if diagnose and treat underlying cause