Skin Scrapes and Their Parasitic Friends

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Skin Scrapes and Their Parasitic Friends

• Clinical Pathology

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Skin Scrape

• Fast and easy diagnostic tool
• Inexpensive
• Should be one of the first diagnostics performed
  when diagnosing dermatologic disorders.

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Items needed for a skin scrape

• Blade (15 or 10)
• Mineral oil
• Microscope slide
• Microscope

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Skin Scraping Technique

• Drop mineral oil on skin and/or slide.
• Some prefer just to pass blade through oil
  instead of applying to skin.
• Gently squeeze the skin area that you are
  scraping. Hold the blade perpendicular to the
  skin.
• Scrape until a small of amount of capillary blood
  oozes. (careful to not cut).
• May place coverslip if you like.
• Examine entire slide in a systematic fashion
  (start with 10x objective)

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Skin Scrape Hints

• Scrape areas that have lesions
• Scrape typical sites for particular ectoparasite
• Ex ear margins for Sarcoptic mange
• Do multiple skin scrapes

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Microscopic exam of the Skin Scrape Sample

• Identify any ectoparasites.
• Determine livedead ratios
• Determine life cycle stage
• Eggs, immature, adults
• Determine numbers found

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Classification

• Class
• Acarina (mites and ticks)
• Family Sarcoptidae and Psoroptidae
• Sarcoptidae
• Mites that burrow through epidermis
• Sarcoptes, Notoedres, Knemidocoptes species
• Psoroptidae
• Mites that reside on the skin surface
• Psoroptes, Chorioptes, Otodectes species

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Sarcoptes Scabei

• Oval with 8 legs
• Long unjointed pedicles with suckers on the end.
• Terminal anus
• Eggs are oval/brownish
• Entire life cycle is on host
• Female mites burrow through epidermis
• Over 10-15 day period 40-50 eggs are deposited in
  tunnels
• Larva emerge in 3-10 days.

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Sarcoptes scabei symptoms

• EXTREME pruritis
• Erythema, papules, scaling, crusting
  excoriations.
• Location Ears, lateral elbow/hock, ventral
  abdomen (termed ventral blowout).
• Scratch reflex When scratch on ear margin, dog
  scratches.

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Sarcoptic Transmission, etc

• Transmitted through direct contact
• Diagnosis is through physical exam and history.
• Since mites burrow into skin is very easy to get
  negative skin scrapes.
• May have to do repeated skin scrapes
• Zoonosis- mites are self-limiting in humans
  (Scabies).

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Sarcoptic Treatment

• Revolution every 2 weeks (off label).
• Ivermectin orally (extra-label).
• Paramite dips every 7-10 days (discontinued
  product).
• NEVER USE PARAMITE CONTAINING DIP IN
  CATS!!!!!!!!!!!!!!!!!!!!!!!!!!!

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Notoedres cati

• Roundish shape, smaller than scabie mite
• Dorsal anus
• Same type of legs as scabie mite
• Mainly found in cats and occasionally in rabbits.
  
• Location Head, neck, ears, back of head and
  sometimes feet.
• Crusts, excoriations, scales
• Pruritis
• Is contagious

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Notoedres cati Treatment

• Revolution/ Ivermectin
• Keep isolated from other cats

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Knemidocoptes Species

• Scaly leg mite of birds
• Burrows under the scales of legs and toes
• Some species may cause depluming around
  head/neck.
• Intense pruritis
• Diagnose through skin scrape
• Treatment Ivermectin????

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Family Psoroptidae Psoroptes cuniculi

• Ear canker mite of Rabbits
• Lesions are dried, flaky crusts within the ear
  canal.
• Pruritic
• Treatment Ivermectin Subcutaneously or topically
  at 2 week intervals.
• Do not clean ears- they are very painful and will
  bleed

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Otodectes cynotis (ear mites)

• Mainly in ear canal, but may be found on any area
  of the body
• Mite feeds on epidermal debris
• Produces intense irritation
• Usually bilateral
• Contagious

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Otodectes cynotis

• Diagnosis
• Grossly see with otoscope or with ear swab
• Treatment
• Ivermectin
• Acarexx topical
• Pyrethrins
• Revolution

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Demodex Species

• Host specific
• Reside in hair follicles and sebaceous glands
• Small numbers are part of the normal skin flora
  of all dogs
• In immunodeficiencies, these mites increase in
  numbers
• Possible genetic predisposition.

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Demodex species

• Demodex canis-dogs
• Demodex cati-cats
• Dmodex gatoi-cats
• Demodex bovis-bovine
• Demodex ovis-sheep
• Demodex caprae-goat
• Demodex equi-horse

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Demodex canis and cati

• Elongated, spindle shape
• Adults 8 stubby legs
• Larvae 6 stubby legs
• When diagnosing demodex cati need to rule out
  underlying disease like Feline Leukemia/FIV, etc.

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Demodex gatoi

• Cats
• Round, blunt body
• Contagious
• Pruritic
• Treatment lyme-sulfur dips

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Demodex canis clinical signs

• Often begin with localized lesions that spread.
• Patchy, multifocal or diffuse alopecia
• Variable erythema
• Silver/grayish scales
• Papules or pustules
• Variable pruritis-localized usually not pruritic
  unless infected
• Secondary lesions- hyperpigmented,
  lichenification, crusty, ulcerated, folliculitis
  from secondary bacteria.

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Demodex canis

• Location of lesions
• Face, muzzle, legs/feet, occasionally trunk.
• Localized or generalized
• Peripheral lymphadenopathy is common due to
  secondary infection.

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Demodex treatment

• Correct/treat underlying conditions
• Neuter/spay
• Treat secondary bacterial infections
• Topical treatment
• Benzoyl peroxide
• Mitaban (Amitraz) dips
• Ivermectin SID
• Increasing oral dose
• Mibemycin
• (interceptor SID)
• Continue treatment one month beyond a negative
  skin scrape.

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Malassezia Dermatitis

• Yeast found in low numbers in the ear canal,
  peri-orally, peri-anally, and moist skin folds
• Almost always associated with underlying disease
  (atopy, food allergy, endocrine disorders)
• Common in dogs- rare in cats

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Malasezzia continued

• Causes moderate to intense pruritis with regional
  or generalized alopecia.
• Chronic changes
• Hyperpigmented
• Lichenificiation
• Hyperkeratosis
• Odorous skin

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Malassezia diagnosis

• Skin scrape and stain, skin imprint, tape prep
• Lesions may involve interdigital spaces, axillary
  region, neck.
• Cytology reveals budding yeast (round to oval)

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Malassezia treatment

• Correct underlying cause
• Shampoos
• Ketoconazol
• Miconazol
• Chlorhexidine
• In severe cases use systemic ketoconazole,
  iatroconazole