Blastomycosis (Systemic Mycoses)

Question 1

What agent causes blastomycosis?

Answer 1

Dimorphic fungi Blastomyces dermatitidis

Question 2

Where (geographically) is blastomycosis more commonly seen?

Answer 2

• Mississippi and Ohio river valleys
• Southern Great Lakes
• Southern mid-Atlantic states
• Seasonality (North; late spring to fall)

Question 3

Which species is affected by blastomycosis?

Answer 3

Mammalian infection

• Dogs
• RARE in cats

Question 4

How is blastomycosis transmitted?

Answer 4

• Inhalation
• Direct inoculation > pyogranulomatous inflammation (lungs, SQ tissue)
  
  • Usually localized
  • May or may not contain disease

Question 5

Who is the poster child for blastomycosis?

Answer 5

Male dogs of hunting breeds, close to rivers

Question 6

What are the clinical signs in a patient with blastomycosis?

Answer 6

• Pulmonary signs (3/4 cases)
  
  • Dyspnea and cough
• Cachexia
• Fever
• Lymphadenopathy
• Cutaneous involvement (draining tracts)
• Ocular lesions
• Bones (osteomyelitis) and joints

Question 7

What do the chest radiographs look like in a patient with blastomycosis?

Answer 7

• Nodular pattern
• Diffuse interstitial or alveolar pattern
• MAY WORSEN WITH THERAPY
  
  • “Snow shower pattern”
  • Systemic inflammatory response

Osteomyelitis of limbs can also be seen

Question 8

How do you diagnose a dog with suspected blastomycosis?

Answer 8

• Find the organism
  
  • Cytology
    
    • Impression smears (all draining tract lesions)
    • FNA
    • Airway washings
  • Histopathology (biopsy of lungs)
• Galactomannan antigen test
  
  • Blast Quantitative EIA test
  • Sensitivity higher in urine than serum
  • Very high cross-reactivity for histoplasmosis (differentiate with cytology)
• Surface Protein BAD-1 (new)
  
  • Good antibody test to differentiate with histo
• Culture (takes time)
• PCR?

Question 9

How do you treat a dog with blastomycosis?

Answer 9

• Fluconazole or itraconazole
  
  • May have to remove eye after therapy (persistent disease)
• Amphotericin B (more severe cases)
• Galactomannan antigen test
  
  • May help determine when to stop therapy (low antigens = stop therapy)
  • Can be used to diagnose relapses

Question 10

What do you tell the owner about the prognosis of blastomycosis in his dog?

Answer 10

• Survival rate is 75%
• Relapse rate is 20%
  
  • Have to treat at least 1 month after clearance of clinical signs and test again