Skin Scrapes and Their Parasitic Friends Clinical Pathology
Skin Scrape • Fast and easy diagnostic tool • Inexpensive • Should be one of the first diagnostics performed when diagnosing dermatologic disorders.
Items needed for a skin scrape • Blade (15 or 10) • Mineral oil • Microscope slide • Microscope
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)
Skin Scrape Hints • Scrape areas that have lesions • Scrape typical sites for particular ectoparasite • Ex: ear margins for Sarcoptic mange • Do multiple skin scrapes
Microscopic exam of the Skin Scrape Sample • Identify any ectoparasites. • Determine live:dead ratios • Determine life cycle stage • Eggs, immature, adults • Determine numbers found
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
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.
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.
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).
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!!!!!!!!!!!!!!!!!!!!!!!!!!!
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
Notoedres cati Treatment • Revolution/ Ivermectin • Keep isolated from other cats
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????
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
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
Otodectes cynotis • Diagnosis: • Grossly see with otoscope or with ear swab • Treatment: • Ivermectin • Acarexx topical • Pyrethrins • Revolution
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.
Demodex species • Demodex canis-dogs • Demodex cati-cats • Dmodex gatoi-cats • Demodex bovis-bovine • Demodex ovis-sheep • Demodex caprae-goat • Demodex equi-horse
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.
Demodex gatoi • Cats • Round, blunt body • Contagious • Pruritic • Treatment: lyme-sulfur dips
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.
Demodex canis • Location of lesions: • Face, muzzle, legs/feet, occasionally trunk. • Localized or generalized • Peripheral lymphadenopathy is common due to secondary infection.
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.
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
Malasezzia continued • Causes moderate to intense pruritis with regional or generalized alopecia. • Chronic changes: • Hyperpigmented • Lichenificiation • Hyperkeratosis • Odorous skin
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)
Malassezia treatment • Correct underlying cause • Shampoos • Ketoconazol • Miconazol • Chlorhexidine • In severe cases use systemic ketoconazole, iatroconazole