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Micro: Deep systemic & opportunistic mycoses

Terms in this set (24)

Blastomyces dermatidis is a saprophytic ____ fungus. 2 phases
Blastomyces dermatidis is a saprophytic dimorphic fungus; 2 phases are mycelial phase & yeast phase
Part of dimorphic fungus; in soil and culture at 25°C; Spores produced on terminal and lateral conidia
mycelial phase
Part of dimorphic fungus; in tissues or culture at ≥37°C; Thick, refractile cell wall
yeast phase
What is the reservoir of Blastomyces dermatidis?
soil (sandy, acid soil near water); Spores survive for long periods, especially when soil enriched with rotting vegetation
How is Blastomyces dermatidis transmitted & to who?
- Primarily inhalation of spores (Transition from mycelial to yeast phase in lung)
- Occasional wound contamination with yeast phase (e.g. dog bite or other accidental contamination)
- Dogs - very sensitive
What are the risk factors for Blastomyces dermatidis?
- Drought, dust, excavation activity, living near water
- Outdoor activity (can occur in strictly indoor animals)
- Season: summer, fall, winter
What animals are at risk for Blastomyces dermatidis?
Cats, horses

Dogs - greater risk : ROAMING
- Sporting and larger breeds
- Intact males
- Age 1-5 years
What are the clinical conditions in dogs & cats associated with Blastomyces dermatidis?
- Asymptomatic infections occur
- Localized in pulmonary system - pneumonia
- Disseminated:
---Signs depend on tissue(s) affected
---Additional sites commonly affected: Skin, bone, eye, lymph node, testes, brain, subcutaneous tissue, external nares
How can you identify Blastomyces dermatidis?
- Thick-walled yeast with single broad-based buds
- Cytology - visible with Giemsa, Wright's
T/F: Blastomyces dermatidis is zoonotic
True
How can you diagnose Blastomyces dermatidis?
- Culture - potential zoonotic hazard
- Serology
- Molecular methods (e.g., PCR)
How should you treat Blastomyces dermatidis?
- Systemic (not topical) anti-fungals
What should you educate the client about Blastomyces dermatidis?
- Treatment required for months to years
- Relapses occur
- Zoonotic transmission possible
- Wear gloves when treating (esp. with exudates)
Histoplasma capsulatum var. capsulatum is a ____ _____ fungus
Histoplasma capsulatum var. capsulatum is a saprophytic dimorphic fungus
Describe the mycelial phase of Histoplasma capsulatum var. capsulatum
In soil; Round microconidia, nodular macroconidia
Describe the yeast phase of Histoplasma capsulatum var. capsulatum
In tissues; Thin cell wall, no capsule
What is the reservoir of Histoplasma capsulatum var. capsulatum?
Soil (sandy, acid soil near water); Spores survive for long periods
What ways is Histoplasma capsulatum var. capsulatum transmitted?
- Microconidia inhaled, possibly ingested
- Increased exposure with excavation, other sources of increased soil turnover & dust
- Converts to yeast phase in lung (37°C)
- Reproduce within macrophages
- Disseminated via macrophages
What are the risk factors for Histoplasma capsulatum var. capsulatum?
Risk factors in dog same as Blastomyces
- Cat can also be affected
What species does Histoplasmosis occur in?
dogs and cats; rare in ruminants, swine, and poultry
Describe Histoplasmosis in dogs and cats.
caused by H. capsulatum var. capsulatum
- May be restricted to pulmonary system (dogs)
- Disseminated disease - progressive, debilitating
- Multiple tissues affected (FYI: liver, spleen, central nervous system, eyes, bone marrow)
How does Histomycosis contrast with Blastomycosis?
Dogs and cats
- Subclinical infections more likely
- Skin involvement uncommon in histoplasmosis
- In dogs, GI involvement is common (rare with blastomycosis)
What are the diagnostics for Histomycosis?
- Cytology
- Histology (Better with special stains)
- Culture - potential zoonotic risk
How do you treat Histoplasma?
- Treatment similar to blastomycosis
-Caution when handling open wounds
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