Fungal Derm Objectives
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- What dermatophytes are pathogenic in dogs and cats?
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-Microsporum canis (most common)
-M. gypseum
-Trichophyton mentagrophytes (seen in rodents)
-Sporotrichosis? - How are Dermatophytes transmitted?
- Dermatophytes are transmitted by contact w/ infected hairs, scales, or fungal elements
- What are typical lesions and distribution patterns of dermatophyte infections in dogs?
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-Classic lesions: annular areas of peripherally expanding alopecia, scale, crust, papules and pustules
-Nasal folliculitis and furunculosis
-Generalized seborrhea-like infection
-Dermatophytic kerion
-Onychomycosis (nail infection)
M. Canis
Head and front limbs
M. gypseum
Extremities and tail
T. mentagrophytes
Whole body - What are typical lesions and distribution patterns of dermatophyte infections in cats?
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-Generalized infections are more common:
-Alopecia
-Folliculitis, erythema, scale, crust, papule
-Generalized seborrhea like eruption
-Milliary dermatitis = uncommon to be caused by dermatophytes (usually caused by fleas)
-Localized infections:
-One or more annular areas of alopecia
-May mimic chin acne or “stud tailâ€
-Onychomycosis
-Dermatophyte kerion
-Dermatophyte pseudomycetoma - How can you positively identify a fungal agent (genus and species)?
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-Most reliable test fore identification = Fungal culture
-Identify the organism through morphologic and microscopic characteristics
-DTM (dermatophyte test medium)
-Dermatophytes utilized the protein in the media first, leading to alkaline metabolites that cause the media to turn red w/in 10-14 days
-Saprophytes utilized carbohydrate first creating acidic metabolites - Why is it important to make a definitive diagnosis for a dermatophyte infection?
- is important to make a definitive diagnosis in order to properly clear up the problem and prevent re-infection
- What recommendations would you make for a cattery w/ dermatomycosis in each litter of kittens (M canis)?
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-Cessation of breeding program
-Identification and isolation of positive animals
-Topical and systemic therapy for positive animals
-Topical therapy for contact cats
-Strict environmental control
-Treat all cats until cats are culture negative 3 times
-Toothbrush cultures to screen healthy appearing cats for carrier status - What skin layer do dermatophytes grow in?
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-Keratogenous zone of keratinized tissue (Adamson’s fringe)
-Hair, nail, stratum corneum of skin
-Don’t affect the hair bulb - Describe the lesions seen with Cryptococcus.
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-Cutaneous lesions including nodules, ulcers and draining tracts
-Nasal discharge and sneezing
-Ocular involvement = blindness
-Neural involvement = seizures, ataxia, paresis - What are the risk factors associated with cryptococcus?
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More common in cats
Found in pigeon shit - How is cryptococcus diagnosed?
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-Cytology
-Biopsy
-Serology - What are the treatment options for Cryptococcus?
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-Itraconazole
-Fluconazole
-Flyctosine - What are the clinical signs of Malassezia dermatitis in a dog?
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-Very pruritic
GENERALIZED:
-Erythematous, greasy, scaly, crusty, malodorous, lichenification, alopecia, hyperpigmentation
LOCALIZED:
-Otitis, lips, muzzle, interdigital spaces, ventral neck, medial thigh, groin, axilla, paronychia, intertriginous regions
-40% have concurrent bacterial pyoderma - What are the clinical signs of Malassezia dermatitis in a cat?
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-Not as common as dog
GENERALIZED:
-Erythematous, scaly to waxy dermatitis
LOCALIZED:
-Otitis, chin acne, paronychia (base of nail) - How do you diagnose Malassezia?
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-Cytologic exam:
-Impression smear, swab, skin scraping, acetate prep
-Look for round to oval budding yeast “peanut shapedâ€
-Skin biopsy w/ histopath
-Culture
-Look for a response to anti-yeast therapy - Discuss Treatment for Malassezia.
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-Identify and address the underlying cause:
-w/ out correction of the predisposing disease or factors, the disease is likely to reoccur
-Treat concurrent Staph pyoderma
Topical therapy:
-Anti-fungal creams or lotions for localized areas
-Anti-fungal shampoos for generalized areas
-Dips are not necessary but can be effective
Systemic therapy:
-Ketoconazole or Itraconazole
-**Griseofulvin is NOT effective**
-Treat 7-14 days past clinical cure - What are the predisposing factors for Malassezia?
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-Increased humidity
-Immune dysfunction
-Genetic (Basset’s or WHWT)
-Hypersensitivity
-Keratinization disorders
-Endocrine or metabolic disorders - Which of the following are zoonotic? Blastomycosis, Histoplasmosis, Coccidiomycosis, Crytococcus neoformans.
- Cryptococcus neoformans
- What are some clinical signs associated with Blastomycosis?
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-Nodular skin lesions
-Draining tracts
-Absscesses
-Often have concurrent respiratory disease - What are some clinical signs associated with Histoplasmosis?
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-GIT and respiratory disease
-Granuloma and draining tract skin lesions - What are some clinical signs of Coccidomycosis?
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Dog:
-Young, male dogs
-Coughing, dyspnea, fever, anorexia, wgt. Loss, lameness, ocular disesase
-Papules, nodules, abscesses, draining tract, ulcers
-Skin infections often occur over infected bone
Cat:
-RARE
-Anorexia, wgt. Loss, cough, dyspnea, lameness, ocular disease, skin lesions - What are some clinical signs of Cryptococcus neoformans infection?
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-Cutaneous lesions include nodules, ulcers, draining tracts
-Nasal discharge
-Ocular involvement = blindness
-Neural involvement = seizures, ataxia, paresis - What are some physical characteristics of Blasto?
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-Broad based budding
-Endemic in Mississippi and Ohio river valley
-Ingested or inhaled from: soil, bird or bat shit - What are some physical characteristics of Histo?
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-Tiny organism
-Endemic in Eastern US - What are some physical characteristics of Coccidio?
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-Largest organism w/ spherules that contain endospores
-Found in sandy, alkaline soil, high temperature, low rainfall, low elevation
-Endemic in SW US, South and Central America - What are some physical characteristics of Cryptococcus neoformans?
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-Large organism
-Relatively common in cats
-Found in pigeon shit
-Thick candy shell - Which breed of dog is predisposed to developing cutaneous infections w/ pythium?
- GSD
- What is the usual source of pythium infection?
- Swamps or ponds in southern US
- How is pythium treated?
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Aggressive surgery (amputation)
-Itraconazole + Terbenafine
-Treat for 2 months and recheck titers at LSU - What is the prognosis for pythium?
- Poor (“swamp cancer†is invasive and often fatal)
- What is an asymptomatic carrier?
- animal that is carrying and possibly shedding a disease without showing any clinical signs
- How are asymptomatic carriers identified?
- Screening tests
- How are Malassezia infections transmitted?
- Malassezia is part of the normal flora of ears and skin. It is an opportunistic pathogen that proliferates under conditions of increased moisture (i.e. greasy, scaly, inflamed skin)
- Does antibiotic therapy predispose animals to yeast or fungal infections of skin?
- Yes
- What is the most common subcutaneous fungal infection of cats and dogs?
- Microsporum canis
- What are the risk factors for infection with Blasto?
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-Found in the Mississippi and Ohio River valley
-Found in nitrogen rich soil and bat and bird shit