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Fungal Skin Diseases
VM 610 Midterm
24
Veterinary Medicine
Professional
11/12/2012

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Term
Dermatophytosis Pathogenesis
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
Term
Dermatophytosis Causes
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
Term
Microsporum canis
Definition
zoophilic in cats
most common cause of dermatophytosis in cats and dogs
Term
Microsporum gypseum
Definition
geophilic
normally found in soil
Term
Trichophyton mentagrophytes
Definition
zoophilic in rodents
Term
Dermatophytosis Predisposition
Definition
younger animals
poor immune system due to FeLV, FIV, cancer, poor nutrition, immunosuppressive drugs, metabolic disease
genetics
Term
Dermatophytosis Zoonosis
Definition
can be transmitted to humans
associated with M canis
every species can be contagious
underdiagnosed in cats
over diagnosed in dogs
Term
Dermatophytosis Lesions in Dogs
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
Term
Dermatophytosis Lesions in Cats
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
Term
Wood's Lamp
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
Term
10-20% KOH
Definition
digests the keratin in hair before microscopic exam of hair
Term
Fungal Culture
Definition
most reliable test
pluck hairs from periphery of a lesion
sterile tooth brush for generalized cases
use Dermatophyte test medium (DTM)
Term
DTM
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
Term
Dermatophytosis Treatment
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
Term
Sporotrichosis
Definition
rose bush dermatitis
saprophyte inoculated via plant thorns or seeds
zoonotic
cutaneous form associated with draining tracts
Term
Pythium and Lagendium
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
Term
Blastomycosis
Definition
endemic in nitrogen rich soil in Midwest
nodular skin lesions, draining tracts, abscesses
often concurrent respiratory disease
Term
Histoplasmosis
Definition
endemic in eastern USA
GI and respiratory disease more common than cutaneous
granulomas and draining tracts
Term
Coccidiomycosis
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
Term
Cryptococcus neoformans
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
Term
Malassezia pachydermatis
Definition
opportunistic when host resistance decreased
concurrent allergies, keratinization disorders, etc.
increased humidity, immune dysfunction, genetics, hypersensitivity,, keratinization disorders, endocrine/metabolic disease
Term
Malassezia pachydermatis Lesions
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
Term
Malassezia pachydermatis Diagnosis
Definition
cytology
shows round to oval budding yeast that are peanut shaped
Term
Malassezia pachydermatis Treatment
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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