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Dermatology - Dermatophytes & Demodicosis

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sihirlifil's version from 2017-10-01 21:35

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Question Answer
Risk factors for DermatophytosisYoung, immunosuppressed
Which species of dermatophytes are zoonotic?All of them
M. canis: host?Normal healthy cat (asymptomatic, passes on to kittens who show CS)
M. canis: fluorecence?Yes, candy-apple green (but can give false negatives, so still culture. Also other chemicals can also glow blue)
M. canis: spread?Grooming, passed to kittens from asymp. mom
M. gypseum: host?Soil
M. gypseum: fluorecence?No
T. mentagrophytes: host?Vermin
T. mentagrophytes: fluorecence?No
Which species of ringworm is the nastiest? Least?Nasty: T. mentagrophytes
Least: M. gypseum
Clinical findings of ringwormAlopecia, crust, scale, epidermal collarette, pustule, papule. Follicles epilate easily
Pustules / papules ddx?Ringworm, bacteria, demodex
Kerion form of ringworm looks like?Nodule (ddx tumor, granuloma, cyst)
Which dx tests should you perform for the kerion form of ringworm?FNA & MACERATED TISSUE CULTURE (tumor vs. inflammation)
Range of severity of ringworm lesions?Variable inflammation (subtle to profound)
(Ddx drug reaction, vasculitis, etc)
Which hairs do dermatophyte affect?ANAGEN (actively growing)
T/F: steroids are indicated in the treatment of dermatophytosisFALSE- need CMI
*Differential diagnoses of ringwormDemodex
Bacterial pyoderma
Seborrheic dermatitis
Endocrine (immunosuppressed are predisposed)
Diagnostic tools for ringwormWood's lamp
Trichogram (KOH prep)
Biopsy
Fungal culture (DTM)
Describe trichogramShould see individual hairs. Pluck, put in oil, look under scope. Dmged cuticle, breaks easily, can see spores
Describe DTM culturePluck hair from outer margin of epidermal collarette, put in agar, see color change to white in 3-7d if positive. Can ID genus and species w/ macroconidia ONLY after culture
Griseofulvin: age? side effects? special thing?Only >12 weeks
Bone marrow toxicity, teratogenic, WILL KILL FIV+ CATS!
Only approved oral antifungal for dogs, cats, horses
Ketoconazole: common tx for? use with who? side effects?Malassezia
NOT FOR CATS!
increase liver enzymes & inhibits CYP450 enzymes (GI SEffx)
Itraconazole: well tolerated? downside? side effects? Works well but $$$
Dermal necrosis in dogs
Fluconazole: well tolerated? First choice for ringworm
Terbinafide: concentrates where? unique?In cornified tissues
It's not an azole (good if seizure dog, atopic dog on Cyclosporine)
Clipping and bathing: risks?Contaminates clipper blads, puts client in more contact with zoonosis when scrubbing
Topical medications for dermatophytosis:Clotrimazole
Miconazole (cheap, good for spots)
Thiabendazole
Ketoconazole
(Terbinafine?)
Avoid steroids
Lime sulfur dip (LSD): Advantages? Disadvantages? Special considerations?Excellent antifungal
Safe, effective, cheap, broad spectrum, antipruritic
Smells terrible (temporarily), stains, tarnishes jewelery
Cats need E-collar! Toxic if ingested
Demodex: etiologyPassed from mother to puppy in first few days of life
Demodex: pathogenesisDogs harbor demodex on body, then stress / immune suppression / endocrine problem --> clinical disease
Where does demodex live?Hair follicles (need deep skin scrape)
T/F pruritis is the most common CS of demodexF. Demodex is not a pruritic dz
Localized demodex: distribution?Feet, face, muzzle (puppies pawing & nursing mom)
Localized demodex: lesionsAlopecia
Localized demodex: TxMay be self-limiting (no tx necessary). Topicals: Rotenone, Goodwinol (but no controlled studies have been done)
Localized demodex: PrognosisUsually self-limiting (=good), but if new lesions develop = becoming generalized
Generalized demodex (juvenile): onset? predispositions?LESS THAN 2 YEARS
Stress predisposes
Generalized demodex: distributionInterdigital spaces, neck, muzzle, abdomen
Generalized demodex: lesionsAlopecia, papules, pustules (+/- hge), collarettes (ddx ringworm!)
Comedones (ddx Cushings, hypothyroid)
Crusts
*Only pruritic if 2ry bacteria present!
Feline demodex: mite spp? general infoDemodex cati, gatoi
Cati = Follicular mite (need deep scrape), only see with another underlying problem
Gatoi = surface mite (superficial scrape), short & stubby w/o tail, causes intense, nonseasonal pruritis. Contagious to other cats, tx whole herd w/ LSD
Unique about Demodex gatoi?CAUSES PRURITIS!
Only treatment available for demodex gatoiLSD applied weekly x 6 (all contact cats) --> usually complete remission
Generalized demodex (adult onset): Underlying causes?Endocrine (hypothyroid, cushings)
Neoplasia
Steroid treatment (Depomedrol)
Idiopathic
Owner wants to breed dog with generalized demodex, you say?Nope... in fact, you should spay/neuter. Will pass along predisposition, affect heat cycle, cause recurrance when in heat again
Common complication of generalized demodex? What do you do about it?2ry Staph infection
Culture and use topical antibx
Amitraz:how do you apply? special thing about it?Clip, shampoo, mix fresh (every time), apply, keep dry. Tx every 2 weeks in the clinic (dont send it home)
It's the only one liscenced for tx the general form in dogs
Cure for generalized demodex defined by2 negative skin scrapings 2 weeks apart (scrape every 2 weeks w/ amitraz tx)
Follow with one more amitraz dip anyway
Side effects of amitrazSedation, dry skin, pruritis, bradycardia, seizures, hypothermia, v+/d+
Yohimbine or Atipamizole are reversals
Alternative tx for demodexMilbemycin - effective but $$$. 2x heartworm dose every day
Ivermectin - off-label and only for >12 weeks and NOT a risk breed! (Collie, shetland sheepdog, border collie, australian shepherd, old english sheepdog) (tox signs: hypersalivation, mydriasis, coma)
Advantage multi (moxidectin) - +/- efficacy, good for scabies
Certifect (amitraz + fipronyl) - not approved
Fluralaner - OVER 6 MONTHS OLD ONLY q 3 months, approved for flea & tick
Sarolaner - >6 months
Afoxolaner - >8 weeks
Generalized demodex: prognosisAlways guarded
Depends on underlying causes & resistance to therapy
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