Mycology: Subcutaneous, Systemic, and Opportunisitc Mycoses

Subcutaneous mycoses spp.

Sporothrix sp.

Systemic mycoses spp.

• Blastomycoses

• Histoplasma

• Coccidioides

• Cryptococcus

Opportunistic mycoses spp.

• Aspergillus

• Candida

Dimorphic fungi mold form

• room temp

• environment

Dimorphic fungi yeast form

• body temp

• 37C incubator

General rule of dimorphic fungi

• pose a risk to personnel

• do not culture in practice

• send to reference lab

Sporothrix schenkii overview

• subcutaneous mycoses

• dimorphic fungus

• species affected: cats, dogs, horses, humans

• transmission:

  • traumatic inocculation

  • inhalation of spores (uncommon)

What species most commonly contracts Sporothrix schenkii?

cats

Clinical presentation of Sporothrix schenkii

• Cutaneous

• cutaneoulymphatic

• disseminated

Cutaneous presentation of Sporothrix schenkii

• abscess → ulcerated, cutaneous nodules

• immunocompetent patients

Cutaenolymphatic presentation of Sporothrix schenkii

• new lesions appear along lymph pathway

• immonocompetent patients

Disseminated presentation of Sporothric schenkii

• viscera, joints, bone, CNS

• immunocompetant cats

• immonsupressed other species

• worst form

Diagnosis of Sporothrix schenkii

• cytology exudate (easiest to see in cats)

  • yeast form: appears round to cigar shaped

• histopathology: biopsy

  • IFA labeling

• serology

• PCR

• contact ref. lab to discuss options

Sporothricosis treatment

• systemic antifungals

• wound debridement as necessary

• wear gloves! zoonotic!

Is sporothricosis zoonotic?

yes

Sporothricosis in humans

• Rose Gardener’s disease

• source: animals, sphagnum moss

Systemic mycoses:

• Blastomyces

• Histoplasma

• Coccidioides

• Cryptococcus

Blastomyces dermatiditidis

• saprophytic dimorphic fungus

  • yeast: thick, refractile wall, broad-based budding

• systemic

what is a saprophytic mycoses?

• obtains nutrients by absorbing dissolved organic material from dead and decaying matter

Geographic distribution of Blastomyces

• reservoir: soil (sandy, acid soil near water)

• spres survive for long periods, especially when soil enriched with rotting vegetation

Transmission of blastomyces

• primarily inhalation of spores

  • transitions from mycelial (mold) phase to yeast phase in lung

• occasional wound contamination

  • dog bite

  • accidental contamination

• dogs: very sensitive

What species is very sensitive to blastomyces?

dogs

Risk comparison of blastomyces in species

dogs > humans > cats > horses

Risk factors for blastomyces

• dorught, dust, excavation activity, living near water

• season

  • summer, fall, winter

  • spring too wet

• dogs greatest risk: ROAMING

  • sporting and larger breeds

  • intact males

  • 1-5 years of age

Clinical conditions of Blastomyces

• asymptomatic infections occur

• localized in pulmonary system - pneumonia

• disseminated

  • signs depend on affected tissues

  • skin, bone, eye, lymph node, testes, brain, subq, external nares

Diagnosis of blastomyces

• identify organism (eg; lymph node aspirate)

  • thick walled yeast with single broad-based buds

  • cytology - visible with Giemsa, Wright’s

• culture at reference lab

• serology

• PCR

Blastomyces treatment

• systemic antifungals

• treatment required for months to years

• relapses occur

• zoonotic transmission possible

• wear gloves when contacting exudate from skin lesions

Histoplasma capsulatum var. capsulatum

• systemic

• saprophytic dimorphic

  • mold: round microconidia, nodular macrocondidia

  • yeast: thin cell wall, no capsule

Histoplasma distribution

• resrvoir: soil (sandy, acid soil near water)

• spores survive for long periods

Histoplasma transmission

• species affected: dogs, cats, humans

• microconidia inhaled, possibly ingested

• increased exposure with excavation, dust exposure

• converst to yeast phase in lung (37C0

• reproduce within macrophages

• disseminated via macrophages

• risk factors same as blasto

Histoplasmosis

• may be restricted to pulmonary system in dogs

• disseminated disease: progressive, debilitating

  • GI involvement

  • multiple tissues affects

Histoplasma diagnosis

• cytology

• histology

  • better with special stains

• culture: potential zoonotic risk

Histoplasma treatment

• similar to blasto- long term systemic antifungals

• caution when handling open wounds

Blasto vs histo in dogs and cats

• Blasto:

  • skin involvement

  • morphology: larger, thick walled, spherical yeasts, borad-based budding

• Histo:

  • GI involvement

  • smaller, oval to spherical yeasts within macrophages

Coccidioides immitis

• systemic

• dimorphic fungus

  • mold: hyphae with thick-walled, barrel-shaped arthroconidia alternating with bridge-like structures

  • yeast: spherules containing endospores

• most virulent fungal pathogen

• potential bioterrorism agent by US gov’t

What is the most virulent fungal pathogen?

coccidioides immitis

Coccidioides immitis distribution

• sandy, alkaline soil

• soil disturbance increases exposure to arthroconidia

• increased release after rainfall

• SW US

Coccidioides immitis transmission

• inhalation of arthroconidia

Coccidiomycosis clinical disease

• all mammals and some reptiles can be infected

• most often in:

  • human

  • dogs

  • horses

  • llamas: appear to be highly susceptible - lung and disseminated forms

Clinical signs of coccidiomycosis in dogs

• 80% lung infection only

  • can cause extensive damage

• 20% disease goes systemic

  • CNS, bone, skin

Diangosis of coccidiomycoses

• cytology: KOH preps of

  • sputum

  • TTW

  • biospy (lymph node, etc)

  • looking for spherules (tissue form of fungus)

• serology

• mycelial (mold) form EXTREMELY dangerous to handle

  • use reference lab

Prevention of coccidiomycosis

• avoid endemic areas as travel

• avoid activities that increase exposure to dust

Treatment of coccidiomycosis

long term systemic antifungals

What is coccidiomycosis called in humans?

Valley fever

Cryptococcus

• C. neoformans and C. gattii

• monomorphic yeast

  • yeast in environment and tissues

• only encapsulated systemic mycoses

  • capsule helps yeast avoid being killed by macrophages

Cryptococcus distribution

• reservoirs:

  • soil

  • bird excreta

  • pigeons: major urban reservoir

• worldiwde distribution

• cats, dogs

• immunocompromised humans

Cryptococcus lifecycle

• dead-end lifecycle from environment to animal

• no animal-animal transmission reported

• most common systemic fungal infections in cats

What is the most common systemic fungal infection in cats?

Cryptococcus

Cryptococcus presentation in cats

• ulcerated facial nodules

• fungal rhinitis

• sneezing

• nasal discharge

• may invade facial bones causing distortion of nasal cavity

• may invade brain → meningitis

Cryptococcus diganosis

• impression smears of lesions

• cytology of body fluids

• india ink stain

  • narrow based budding

  • big capsule

• fungal culture

  • SDA

• serology - ELISA

Treatment of cryptococcus

• long term systemic antifungals

• treatment continues for 1-2 months past clinical sign resolution

• may require surgical removal

• tx of cryptococcal rhinitis largely unsuccessful

Opportunistic mycoses

• Aspergillus

• Candida

Aspergillus spp

• ubiquitous in environment

  • plant debri

  • soil

• constant aerosol exposure inevitable

• monomorphic mold

Species of Aspergillus affecting animals

• A. fumigatus

• A. flavus

• A. nidulans

• A. niger

Aspergillus clinical disease

• pneumonia

• systemic disease

• cutaneous disease

• guttural pouch mycosis in horses

• chronic rhinitis/epistaxis in dogs

• abortion in cattle/horses

• brooder pneumonia in poultry

Aspergillus diagnosis

• complicated by ubiquitous nature

  • common contaminant

• sample from visualized lesion

  • direct microscopy

  • culture

Aspergillus tx

• depends on presentation

• systemic vs. topical

Aspergillus human opportunistic infection

• immunosuppressed

  • AIDS

  • chemo

  • cystic fibrosis

• majority from environment

  • NOT readily zoonotic

Candida albicans

• monomorphic yeast

• normal flora on mucosal surfaces

• opportunistic

  • antibitoic treatment → disruption of normal bacterial flora

  • immunosuppression

Candid causes

• thrush in poultry/crop mycosis

• forestomach of calves

• oral, esophageal, gatric of porcine

• oral, esophageal of foals