Demodicosis Flashcards
What is the life cycle of demodex?
- normal inhabitant of the skin
- obligate parasite
- life cycle: 25-30d
- females lay eggs in hair follicles/glands
- eggs hatch into 6-legged larvae
- larvae molt to 8-legged nymphs
- nymphs molt to 8-legged adults
- adult mites in hair follicles, sebaceous glands and sweat glands
- feeds on cellular debris
How are mites transmitted?
- to pups from bitch in first 1-3d of life
- present in low #s in healthy post-natal dogs
- dz caused by abnormal proliferation
What is the pathogeneiss of demodicosis?
- deficient cell mediated immune response
- involved in progression of dz
- genetics, autosomal recessive
- juvenile onset, generalized
- immunosuppression
- juvenile onset: poor nutrition, stress, estrus, endoparasites
- adult onset: steroids, endocrine dz, neoplasia
- Bacterial folliculitis
True or False: Demodicosis is contagious and zoonotic
false! neither contagious nor zoonotic
What are the clinical signs of demodicosis?
- pupules/pustules, erythema
- alopecia
- scaling, crusting
- comedones (follicular plugging)
- patchy alopecia
- hyperpigmentation
How do you diagnose demodicosis?
- three techniques:
- deep skin scrapes
- hair plucks
- biopsy:
- Shar pei
- Scar tissue
- pododermatitis
What are the various times of onset of demodicosis for small vs. large vs. giant breeds
- Small breeds: 12 mo
- Large breeds: 18 mo
- Giant breeds: 24 mo
* juvenile onset <; adult onset >
What is juvenile onset localized demodicosis?
- evidence of mites in one area based on 5 deep skin scrapes –> benign
If you diagnose demodez on a deep scrape, what two questions should you ask?
- Is it generalized?
- scrape 5 places total
- If not, will it become generalized?
- don’t treat, wait and see
What are two reasons you must know if the disease will generalized?
- To know/discuss prognosis
- To make recommendations about spaying/neutering
What percentage of localized demodicosis will clear spontaneously vs. generalize?
- Clear spontaneously (us. in 6-12 wks) = 90%
- Generalize = 10%
good prognosis for juvenile onset localized demodicosis
How should you treat juveline onset localized demodicosis?
- benign neglect
- antibiotics - esp. if pustular
- topical: 2% mupirocin, benzoyl peroxide gel/shampoo
- systemic (if needed)
- de-worming, good diet, HW prev, TLC
- No steroids or anti-mite tx
Why shouldn’t you treat localized demodicosis with miticides?
- to know if it will become generalized
- prevent unnecessary medical tx
How do you tell if localized demondicosis is become generalized?
- monitor the course of dz
- recheck in 2-4 wks
-
deep skin scrape same 5 spots
- if mite counts decr: lesion resolving, recheck q., 4 weeks until neg
- if mite counts incr (+/-) other sites + for mites: may be progressing to generalized
Describe generalized demodicosis
- 5 localized lesions or more
- involvement of an entire body region (ex: the head)
- involves 2 or more feet = pododemodicosis
What percent will self-clear in juvenile-onset, generalized demodicosis?
- 50% will self-clear
- 50% need anti-mite tx
- 95% will resolve with tx
- 5% will need life-long tx
Describe adult-onset generalized demodicosis
- age: >1-2 yrs (breed dependent)
- differentiate from a juvenile onset case –> never cleared or diagnosed
- underlying immunosuppression
- steroid misuse
- endocrine dz
- metabolic dz
- neoplasia
Define pododemodicosis
- demodicosis of 2+ feet
- generalized demodicosis
- often chronic and resistant to therapy
How do you treat generalized demodicosis?
- miticide
- antibiotics
- treat secondary bacterial infections
- until first negative scrape
- benzoyl peroxide shampoo
- follicular flushing
What are 3 treatment options to kill mates?
- Amitraz - Mitaban
- Ivermectin - Ivomec
- Milbemycin - Interceptor
Describe Amitraz
- only FDA approved tx
- mechanism: monoamine oxidase inhibitor, alpha adrenergic agonist, inhibits prostaglandin synthesis
- clip hair short, bathe with benzoyl peroxide shampoo before dipping
- benzoyl shampoo - follicular flushing
- label use: 1 vial/2 gallons H2O q 2 wks
- in reality: dip once weekly
- do not bathe or get wet in b/t dips
- need gloves and ventilation
- dip until 3 neg consecutive scrapings 2-4 wks apart
What patients should you be concerned for when treating with Amitraz?
- Toy breeds
- sick, old patients
- extensive ulcerations
What are the side effects of Amitraz?
- sedation/dull mentation
- reversal agents:
- Yohimbine
- Atipamezole
- avoid use in owners with:
- asthma
- diabetes
- owner taking a MOA: Parkinson’s dz
What are some causes of failure with Amitraz treatment?
- steroids
- Staph pyoderma not treated
- concurrent dz
- genetics
- long hair, bath b/t dips
- poor owner compliance
- premature discontinuation of tx
*no improvement after 6-9 dips
Describe Ivermectin
- off label
-
use in amitraz resistant cases, animals that do not tolerate the dips
- build up to final dose slowly
- watch for neuro side effects
- tx until 3 consecutive negative scrapes
What breeds should ivermectin not be used in?
- Collies/Border collies
- Shelties
- OESD
- Aussies
- “White feet don’t treat”
What does the MDR1 gene deletion cause?
- defect in protein pump (P-glycoprotein)
- drug crosses into brain but is not pumped out efficiently
Describe Moxidectin
- Advantage multi
- weekly or every other week application
- systemic absorption
- less effective than oral ivermectin but possible options for dogs that cannot take ivermectin
- off label use of this product
Describe Bravecto (flurolaner)
- highly effective in eliminating Demodex
- 1 pill eliminated 100% of mites by day 56
- More effective than Advantage Multi once monthly
- currently labeled for Demodex
- safe for MDR1 breeds
Describe Nexgard and Simparica
- both tx are effective in killing Demodex
- Safe for ivermectin sensitive breeds
- oral, once a month
How do you monitor therapy for generalized demodicosis?
- 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 skin scrapes at 4 wk intervals
What is the prognosis for generalized demodicosis?
- 97% juvenile onset, generalized clear with proper tx
- important factors:
- proper dipping/admin of meds
- proper skin scrapings (DEEP)
- abx tx –> correct dose/adequate time
- 3 neg, consecutive skin scrapes
- clinically normal dog can be positive for rare demodex
- Breeds difficult to clear: OESD, Afghan hound, shih tzu, lhasa apso
- spay/neuter: heat cycle can cause incr in mite counts: do once pyoderma clears, before or at first neg skin scrape
Describe adult onset generalized demodicosis
- look for underlying cause
- treatment options - same as juvenile onset demodex
- px: depends - do you find the underlying cause? Can you control it?
Describe feline demodicosis
- uncommon to rare (varies geographically)
- two species of mite:
- D. cati and D. gatoi
Describe demodex cati
- follicular mite
- variable pruritus
- head and neck
- immunosuppressed- Generalized
- diabetes
- FeLV/FIV
metabolic dz
- long and narrow
- Dx: deep skin scrape
Describe Demodex gatoi
- Stratum corneum mite
- contagious
- can be very pruritic
- trunk
- head and neck
- short and wide
- common in Texas
- Dx: superficial skin scraping
What are the clinical features of feline demodicosis?
- localized/generalized
- alopecia
- scaling
- erythema
- hyperpigmentation
- ceruminous otitis
- +/- pruritus
How do you diagnose feline demodicosis?
- broad SUPERFICIAL skin scrapes for D. gatoi
- dorsal neck/lateral
- antebrachium
- may be difficult to find
- parasite is superficial
- good groomers
- deep skin scrapes 3-5 sites for D. cati
- localized vs. generalized
How do you treat D. cati?
- Ivermectin PO or SQ weekly x 6 wks
- LymDyp: 1-2% lime sulfur - unknown benefit
- Not rx: Amitraz
- spontaneous resolution is possible
How do you treat D. gatoi?
- LymDyp: 1-2% lime sulfur
- miticidal
- anti-bacterial
- anti-pruritic
- tx all cats in contact
- E-collar until dry to prevent:
- oral ulcers
- GI upset
