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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