Demodicosis (Marsella) Flashcards
Demodex canis Life Cycle
- 25-30 days
- Egg → larvae (6 legs) → Nymph (8 legs) → adult (8 legs)
Demodex transmission
- Mites transmitted from bitch to pups
- Present in low numbers in healthy, post-natal dogs
- NOT contagious
- NOT zoonotic
Demodex pathogenesis
- Deficient cell-mediated immune response
- Genetics (autosomal recessive)
- Immunosuppression
- Bacterial folliculitis (Staph is an immunosuppresant)
Common causes of immunosuppression in juveniles
- Poor nutrition
- Stress
- Estrus
- Endoparasites
Common causes of immunosuppression in adults
- Steroids
- Endocrinopathies
- Neoplasia
(Demodicosis usually presents before the underlying disease does)
Clinical signs of demodicosis
- Papules/pustules
- Erythema
- Scaling
- Crusting
- Comedones
- Patchy alopecia
- Hyperpigmentation
Differential diagnosis list for comedones
- Demodex!!!
- Endocrine disease
Demodicosis diagnosis
- Deep skin scrapes
- Hair plucks (negative does not R/O)
- Biopsy (Shar peis, scar tissue, pododermatitis)
Onset of juvenile onset demodicosis
- Small breed < 12 mos
- Lrg breed < 18 mos
- Giant breed < 24 mos
Onset of adult onset demodicosis
- Small breed > 12 mos
- Lrg breed > 18 mos
- Giant breed > 24 mos
Juvenile onset localized demodicosis
Evidence of mites in one area based on 5 deep skin scrapes. Benign.
Questions to ask with deep skin scrape of demodex
- Is it generalized?
- Scrape 5 places total
- If not, will it become generalized?
- Don’t tx, wait and see
Prognosis for localized demodicosis
- 90% will clear spontaneously in 6-12 wks
- 10% will generalize
- Prognosis good
Treatment for juvenile onset localized demodicosis
- Benign neglect
- Abx (esp. if pustular)
- Topical 2% mupirocin, benzoyl peroxide gel/shampoo
- Systemic
- De-worming, HW prevention
- Good diet
- Supportive
Treatments to avoid in juvenile onset localized demodicosis
- Steroids
- Anti-mite therapy
Why not treat localized demodicosis w/ miticides?
- To know if it will become generalized
- Prevent unnecessary medical treatment
Localized demodicosis recheck
- 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
Generalized demodicosis
- 5 or more localized lesions
- Involvement of an entire body region (ex. head)
- Involves 2 or more feet (pododemidicosis)
Cause of juvenile onset generalized demodicosis
Hereditary
Juvenile onset generalized demodicosis prognosis
- 50% self clear
- 50% need anti-mite treatment
- of those that need treatment, 5% need lifelong treatment
- 97% clear w/ proper tx
Adult onset generalized demodicosis
- Age > 1-2 yrs
- Differentiate from a juvenile onset case that was never cleared/diagnosed
- Underlying immunosuppression
Pododemodicosis
- Generalized demodicosis
- Involves 2+ feet
- Often chronic and resistant to therapy
Generalized demodicosis treatment
- Treat underlying cause
- Miticide
- Abx (2º bacterial infections)
- until 1st negative scrape
- Benzoyl peroxide shampoo
- Follicular flushing
Amitraz (Mitiban)
- 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
Amitraz (Mitiban) contraindications
- Toy breeds (need to dilute more)
- Cats
- Sick, old patients
- Extensive ulcerations
Amitraz (Mitiban) adverse effects
- Sedation/dull mentation
- reversal agents available if too severe (yohimbine, atipamezole)
- Owners w/
- asthma
- diabetes
- taking MAO (Parkingson’s disease)
Amitraz (Mitaban) failure
- No improvment after 6-9 dips
- Causes: steroids, untreated Staph pyoderma, concurrent dz, genetics, long hair, bath between dips, poor owner compliance, premature discontinuation
Ivermectin (Ivomec)
- 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
Ivermectin contraindicaitons
White feet don’t treat
Collies, border collies, shelties, old english sheep dog, aussies
MDR1 gene deletion
- 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
Moxidectin (Advantage Multi)
- 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
Bravecto (flurolaner)
- 1 pill eliminated 100% of mites by day 56
- More effective than monthly Advantage Multi
- Safe for MDR1 breeds
Generalized demodicosis monitoring
- 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
Factors effecting prognosis of generalized demodicosis
- Breeds difficult to cure: old english sheep dog, Afghan hound, shih tzu, lhasa apso
- Heat cycle can cause incr. in mite count (spay/neuter)
When to spay/neuter w/ generalized demodicosis
- 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
Adult onset generalized prognosis
Depends on if you can find and control underlying cause
Demodex cati
- Follicular mite (long & skinny)
- Deep skin scrape
- Variable pruritis of head & neck
- Immunosuppressed (generalized)
- Diabetes, FeLV, FIV, metabolic dz
Demodex gatoi
- Stratum corneum mite
- Superficial skin scrape
- Contagious
- Can be very pruritic
- Trunk, head, neck
Feline Demodicosis clinical features
- Localized or generalized
- Alopecia
- Scaling
- Erythema
- Hyperpigmentation
- Ceruminous otitis externa
- +/- pruritis
Feline demodecosis diagnosis
- Broad superficial scrape for D. gatoi
- Dorsal neck/lateral, antebrachium
-
Deep scrapes at 3-5 sites for D. cati
- local vs. generalized
Demodex cati treatment
- Ivermectin
- LymDip (lime sulfur dip)
- Spontaneous resolution possible
Demodex gatoi treatment
- LymDip (lime sulfur dip)
- Cone until dry to prevent oral ulcers & GI upset
- Treat all cats in contact
Feline demodicosis prognosis
-
D. gatoi
- excellent w/ tx
-
D. cati
- poor if unable to find underlying cause
- good if diagnose and treat underlying cause
