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*Mycology-2012: General Features
*kingdom FUNgi (~ 400 pathogenic species)
* Eukaryotic, nonphotosynthetic,
* filamentous or unicellular
*Rarely Epidemic (ie. Contagious)
* Exception (Dermatophytes) - zoonotic
* Endemic – Yeast, Dimorphic fungi – saprozoonotic
* Predisposing factors
* environment load, immune status, prolonged Abx
*Asexual reproduction
*spore structures impt. Dx tools
*General Diagnostic Lab Procedures
*Rapid Dx
* 10 - 20% KOH wet mount
*Histological Stains:
* PAS (Periodic Acid Schiff) – stain red
* Methenamine Silver – brown or black
* H+Eosin (Histoplasma)
* India Ink (Cyptococcus)
*PCR
* IDEXX has Systemic Fungal package Dog/Cat
*Culture
* Sabourauds Media (culture temp. 22 - 25 oC)
* Scotch Tape Mount - Lactophenol Cotton Blue (LPCB)
*MALDI-TOF mass spec
India ink PAS
Methenamine silver
10% KOH of skin/hair - arthrospores
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Fungal Cell Envelope & Some Antifungals
Erg Erg
1,3-β glucan synthase
1,6-β glucan
Chitin
Echinocandins – Capsofungin “Penicillin of Antifungals”
‘Azoles - Ketoconazole - Itraconazole
Allylamine - Terbinafine
1,3-β glucan
Lanosterol
Squalene
Mannoproteins
= Ergosterol
Polyenes Amphotericin B
I. Opportunistic Mycoses:
- Candidiasis – brooder pneumonia in chicks, mycotic stomatitis & mastitis
- Aspergillosis
- Zygomycosis
II. Cutaneous and Subcutaneous Mycoses:
- Dermatophytes,
- Malassezia pachydermatitis – otitis externa dogs, less commonly dermatitis (dogs)
- Sporothrix schenckii – ascending ulcerative lymphangitis (horses), disseminates (cats)
III. Systemic Mycoses:
- Cryptococcosis, Histoplasmosis, Blastomycosis & Coccidioidomycosis
IV. Fungal –like pathogens: an Algae, Mycotic Swamp Cancer … FYI
*The Fungal Pathogens
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* I. Opportunistic Mycoses: Aspergillosis
* Aspergillus fumigatus (others)
* Inhalation/ingestion of spores (poor hay/silage)
*Brooder pneumonia in chicks (contaminated litter)
*Guttural Pouch Mycosis
* Unilateral, internal carotid erosion (lethal bleed-out)
* Epistaxis, mucopurulent nasal discharge, dysphagia/laryngeal paralysis
*Nasal Aspergillosis in Dogs
* serosanguinous nasal discharge, epistaxis
* ulceration external nares
* turbinate destruction
*Aspergillemia – Abortion cattle/horses
* I. Opportunistic Mycoses: Zygomycoses
*Aseptate fungi - Rhizopus, Mucor and Mortierella
* Inhalation/ingestion/cutaneous puncture
*Angiotrophic – hematogenous dissemination
*Cattle (horses, swine, companion etc.)
*Cattle - Abortion, pneumonia
*Mortierella wolfii – cattle
* first Canadian case (CVJ, 51:2010): abortion & brain & pneumonia % kidney
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Dx: Aspergillosis & Zygomycosis • Direct examination: Septate, branching
• Dogs/Horses – radiology and/or rhinoscopy
• SAB, Colony characteristics, LPCB
• Direct exam’n: Aseptate, wider hyphae
• Culture (SAB) easy
• establishing cause!
Methenamine silver
+ green counterstain
Mucor
Close-up colony, aerial hypha & sporangia
rhizoid
II. Cutaneous Mycoses: Dermatophytoses
“Ringworm” – contagious, zoonotic
Circular alopecia, erythema
No systemic disease
Arthroconidia/spores Penetrate skin at abrasions
Germination hyphae stratum corneum + hair follicles
Microsporum & Trichophyton spp.
M. canis – most common in cats
M. gypseum - rodents, dogs, horses
T. verrucosum - most common in cattle (occasionally in sheep, horses, humans)
T. equinum - most common in horses
T. mentagrophytes - rodents (guinea pigs, mice), dogs and more..
“asbestos” plaques)
M. canis
T. verrucosum
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Dermatophytoses: Diagnosis
Ringworm lesions
Woods’ Lamp (M. canis only)
10 - 20% KOH + LPCB
Direct examination - arthrospores/hyphae
Routine Culture : SAB
Up to 8 wks, room temp.
Colony morphology, color
Scotch tape wet mount (LPCB)
Septate Hyphae & macroconidia
PCR-Dx coming
Txt – environmental spores
Decisions on transmission
Itraconazole cats, dogs
Griseofulvin – cattle/horses (teratogenic)
10% KOH - arthrospores
III. Overview of Systemic Mycoses
Infections in healthy animals; Txt with Itraconazole or Amphotericin B
Saprozoonoses
Inhaled (ingested) from environment source
Upper Resp. or Lungs –
Secondary hematogenous dissemination
Cryptococcosis (Risk group 2) – only encapsulated systemic fungi
Blastomycosis (Risk Group 3): thermally dimorphic
Histoplasmosis (Risk Group 3): thermally dimorphic
Coccidioidomycosis (Risk Group 3 : Coccidioides immitis/posadasii
○ dogs, horses, humans – endemic, prevalent southwestern U.S.
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Cryptococcosis: True (Monomorphic) Yeast
Cryptococcus neoformans (C. gattii )
soil contaminated with pigeon feces
CATs (most common systemic fungal), dogs, humans
Saprozoonoses, immune status is factor
Pathogenesis - Inhalation unencapsulated form
Nasal mucosal colonization rhinitis Capsule forms (antiphagocytic/ immunosuppressive) hematogenous dissemination
Skin, eyes, lungs, kidney, joints, CNS
India ink
SAB Encephalitis: PAS
- Serology
- PCR (IDEXX)
Environmental
Source - Lime
CA NV
TX
AZ
UT
NM
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Blastomyces dermatitidis: Blastomycosis
DOGs (cats, humans rarely others)
Severe resp./skin disease in dogs
Slightly acidic, organic soils, water sources, beaver dams
SK/MN/ON, St. Lawrence River
Miss. R
Ohio R
Tennessee
Great lakes
Pathogenesis: chronic pulmonary infect’n
Aerosol inhalation
○ pyogranulomatous lesions in lungs, regional L.N.
○ Hematogenous - skin, eyes, bone, brain,
Blastomycosis: Dx/TxT
Hx: Dog, endemic area, signs
Direct Examination – Yeast form
Exudates: skin, respiratory (TTA)
Thick-walled yeast, 5-20 m
Histo – PAS/Methenamine silver
Culture : Mycology Reference Lab SAB 2-8 wks (20oC) - septate, Lollypop chlamydospores
BHI (37oC) - budding yeast
Serology – reference lab, PCR (IDEXX)
Direct Zoonoses rare .. But post bite, post necropsy (vets)
TTA
Lollipop Chlamydospores
Methenamine silver
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Histoplasma capsulatum: Histoplasmosis
Facultative intracellular pathogen
Soil, decaying vegetation, feces (bats, pigeons, starlings)
Humans, dogs (< 4 yrs), cats
Pathogenesis/Signs: often asymptomatic
Dogs – anorexia, resp. signs, diarrhea mild-severe necrotic granulomatous pneumonia
GIT colon/rectal mucosal ulceration Hematogenous spread less common
Histoplasmosis: Dx/Txt
Direct examination: Intracellular
Aspirates (TTA, LN, bone marrow)
Rectal mucosal scraping
H & E, Wright’s, Giemsa, PAS
Culture : SAB (20oC) + BHI (37oC)
Mold phase septate, tuberculate chlamydospores
BHI (37oC) – budding yeast
Serology – ELISA, PCR (IDEXX)
Tuberculate
chlamydospores
Scotch tape - LPCB
Blood smear
or buffy coat