Term
| Dermatophytosis Pathogenesis |
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Definition
keratinophilic fungal organisms feed on stratum corneum, nails, and anagen hair
trauma facilitates dermatophyte invasion
hyphae proliferate on hair surface
produce keratolytic enzymes that penetrate hair cuticle
hyphae migrate down hairshaft until it reaches keratogenous zone
then it produces toxins which may lead to cutaneous inflammation
these toxins contribute to clinical signs and cell mediated immunity
it also produces other substances that can cause local suppression of cell mediated immunity which may contribute to persistent/recurring infections |
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Term
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Definition
more common in hot, humid, environments
transmitted by contact with infected hairs, scales, or fungal elements
hair shafts in environment may be infectious for months |
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Term
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Definition
zoophilic in cats
most common cause of dermatophytosis in cats and dogs |
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Term
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Definition
geophilic
normally found in soil |
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Term
| Trichophyton mentagrophytes |
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Definition
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Term
| Dermatophytosis Predisposition |
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Definition
younger animals
poor immune system due to FeLV, FIV, cancer, poor nutrition, immunosuppressive drugs, metabolic disease
genetics |
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Term
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Definition
can be transmitted to humans
associated with M canis
every species can be contagious
underdiagnosed in cats
over diagnosed in dogs |
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Term
| Dermatophytosis Lesions in Dogs |
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Definition
annular area of peripherally expanding alopecia, scale, crust, papules, and pustules
often affects face, limbs, paws, tail
nasal folliculitis and furunculosis
generalized seborrhea like infection
dermatophytic kerion
onychomycosis |
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Term
| Dermatophytosis Lesions in Cats |
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Definition
generalized infections or more common
alopecia
folliculitis, alopeci, erythem, scale, crust, ppules
generalized seborrhea-like eruption
miliary dermatitis is usually caused by fleas
can have localized infections like dogs |
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Term
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Definition
used to diagnose dermatophytosis
must warm up a few minutes before use
infected hair fluoresce yellow-green
white color is negative reaction
only 50% of M canis glow |
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Term
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Definition
| digests the keratin in hair before microscopic exam of hair |
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Term
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Definition
most reliable test
pluck hairs from periphery of a lesion
sterile tooth brush for generalized cases
use Dermatophyte test medium (DTM) |
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Term
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Definition
dermatophytes use protein in media first
this leads to alkaline metabolites to form which cause the media to turn red in 10-14 dys
saprophytes use carbohydrates first and make acidic metabolites and cause the media to turn red after 14 days when they start to use protein
do not rely on color changes
must identify organism through morphologic and microscopic characteristics |
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Term
| Dermatophytosis Treatment |
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Definition
spontaneous resolution with localized infections not generalized infections
correct any underlying problems
reduce contagion
hasten resolution of infection with antifungal shampoos and dips and systemic therapy
continue until 3 negative cultures |
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Term
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Definition
rose bush dermatitis
saprophyte inoculated via plant thorns or seeds
zoonotic
cutaneous form associated with draining tracts |
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Term
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Definition
aquatic organisms
may cause cutaneous and/or systemic disease
GI disease with pythium
large vessel invasion with lagendium
German Shepherds predisposed
invasive and often fatal
often have to amputate
hyphae are hard to find on stains
progressive and invasive |
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Term
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Definition
endemic in nitrogen rich soil in Midwest
nodular skin lesions, draining tracts, abscesses
often concurrent respiratory disease |
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Term
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Definition
endemic in eastern USA
GI and respiratory disease more common than cutaneous
granulomas and draining tracts |
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Term
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Definition
Coccidiodes immitis
endemic SW USA
coughing, dyspnea, fever, anorexia, weight loss, lameness, ocular disease
papules, nodules, abscesses, draining tracts, ulcers
more common in dogs than cats |
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Term
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Definition
common in cats
organism found in pigeon droppings
nodules, ulcers, draining tract
nasal discharge, sneezing
ocular involvement leading to blindness
neural involvement leading to seizures, ataxia, paresis |
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Term
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Definition
opportunistic when host resistance decreased
concurrent allergies, keratinization disorders, etc.
increased humidity, immune dysfunction, genetics, hypersensitivity,, keratinization disorders, endocrine/metabolic disease |
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Term
| Malassezia pachydermatis Lesions |
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Definition
very pruritic
generalized form: erythema, greasy, scaly, crusty, malodorous, lichenification, alopecia, hyperpigementation
Localized form: anywhere
can have concurrent bacterial pyoderma
more common in dogs |
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Term
| Malassezia pachydermatis Diagnosis |
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Definition
cytology
shows round to oval budding yeast that are peanut shaped |
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Term
| Malassezia pachydermatis Treatment |
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Definition
identify and address underlying cause
treat concurrent staph pyoderma
antifungal creams, lotions, shampoos
systemic therapy
treat 1-2 weeks past clinical cure |
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