37 – Dimorphic Fungi Flashcards
1
Q
Microbiological characteristics
A
- 2 forms: mycelial (mold) AND yeast
- Some are thermally dimorphic (B. dermatitidis, H. capsulatum, S. schenckii complex): at 37C=yeast phase, under that=mycelial phase
- Level 3: mycelial form
- Level 2: yeast form
2
Q
Blastomyces dermatitidis natural host or habitat
A
- Acidic soil
o Soil particularly near water
o Recent EXCAVATION - *eastern NA, swift current, Regina, CANORA, ON! (not in BC, AB)
- *Africa
3
Q
Coccioioides immitis natural host or habitat
A
- Soil of low elevation deserts
- *SW USA (Phoenix and Tucson)
- *shifting with climate change (‘valley fever’)
4
Q
Histoplasma capsulatum natural host or habitat
A
- Nitrogenous soils
o Association with bat/bird feces
o *SE USA
5
Q
Sporithrix schenckii complex natural host or habitat
A
- Old wood, rose thorns, moss
o S. brazillensis: cats - *Mexico and southern Texas(S. schenckii)
- *Brazil (S. brasillensis)
- *china (S. globosa)
6
Q
Blastomyces virulence factors
A
- Spores produced by environmental mycelial phase
o Inhaled (respiratory infection) OR
o Inoculated into skin (skin infection)
7
Q
Coccidioides virulence factors
A
- Arthroconidia very small and easily picked up by wind and inhaled
o Once reach alveoli=transform into thick-walled spherules which on maturity FILL UP endospores (can see on histopath/cytologoy) - *STRONG WINDS FOLLOWED BY RAIN (weather component)
8
Q
Histoplasma virulence factors
A
- Spores produced by environmental mycelial phase of fungus are INHALED and converted to yeast form
- *travels to lymph nodes and then disseminates throughout the body
- *pigeons and bats (ex. attics)
9
Q
Sporothrix spp. virulence factors
A
- Live in environment
- Exposure related to CONTACT with PLANT MATERIAL (rose bushes, sphagnum moss, hay and dry wood)
- *infection via puncture wounds
- S. schenckii: plant material
- S. brazilliensis: cat bite wounds
10
Q
What are the clinical signs of B. dermatitidis in dogs?
A
- Respiratory disease (85% have lung lesions): nodular and diffuse
o Radiographs and likely treated with antibiotics and have NOT gotten better - Ocular signs frequently observed (40% uveitis)
- Skin lesions: 20-50%
- Anorexia, weight loss, lameness
- *low grade signs for days to weeks to months (ACUTE PROGRESSION AND ANIMAL WORSENS)
11
Q
What is B. dermatitidis in dogs most common in?
A
- Young, large breed dogs
- Sporting breeds and hounds
- Proximity to waterways and exposure to excavation
- *dogs 10x more susceptible than people (can serve as a sentinel)
- *THE ONE FROM THIS LECTURE YOU ARE MOST LIKELY TO SEE!
12
Q
B. dermatitidis in people
A
- Starts as respiratory infection
o Dry cough
o Fever
o Weight loss - Bone=most common extra-pulmonary involvement
- *Mississippi state=highly endemic region
- (if suspect patient has it, ask about clinical disease in family members)
13
Q
What is the colloquially term for the disease caused by Coccidioides spp.?
A
- “valley fever”
o C. immitisi OR C. posadassi depending on location
14
Q
Coccidioides spp. infection in dogs and clinical signs
A
- Subclinical infections common (70%)
- Clinical signs depend on site of infection
o LAMENESS most common
o Chronic illness
o Respiratory signs
o Lymphadenopathy
o Non-healing cutaneous lesions
15
Q
When do you most commonly see infections with Coccidioides spp. in dogs?
A
- Following heavy rainfall
o Epidemics have occurred following dust storms AFTER RAIN (arthroconidia are picked up by wind)
16
Q
Geographic region and being at risk as a dog to Coccidioides spp.?
A
- Potential exposure in past 3 YEARS!
- Travel history?
