Blastomyces — Culture and Identification

This page provides testing information for Blastomycosis at Public Health Ontario (PHO). The causative agent(s) of Blastomycosis in North America are Blastomyces dermatitidis and Blastomyces gilchristii; testing typically does not differentiate between these two species.

The following testing options are available for Blastomycosis:

1. Fungal culture
   Includes initial direct microscopic examination of clinical specimens that may provide a rapid preliminary diagnosis when Blastomyces yeast forms are observed.
   If sending a specimen to PHO requesting for isolation, culture and identification of Blastomyces, please refer to testing information: Mycology — Fungal Culture – Systemic.
   
   
2. Culture confirmation 
   If sending a cultured isolate suspected as Blastomyces to PHO to confirm identification, please refer to testing information: Mycology — Reference Identification of Yeast, Filamentous Fungi and Nocardia/Aerobic Actinomycetes.
   
   
3. Serology
   If sending blood sample (serum) to PHO for investigation of serologic evidence of Blastomyces infection, please refer to testing information: Blastomyces — Serology.

For general public health information about blastomycosis, including disease transmission, symptoms, risk factors, prevention, and epidemiology, visit PHO’s Blastomycosis webpage.

For educational information on blastomycosis in Ontario, including disease epidemiology, clinical manifestations, diagnostic approaches, and public health considerations, refer to our resource: Blastomycosis in Ontario: Public Health and Clinical Considerations.

About Blastomycosis

• Geographic distribution: Blastomyces dermatitidis and Blastomyces gilchristii are endemic to large areas of North America.  In Canada, blastomycosis occurs most commonly in Manitoba, Quebec, and Ontario, however cases have also been reported in other provinces. North-western Ontario is a hyperendemic region although cases have been identified throughout the province. In the United States of America, endemic areas include Michigan, Wisconsin, Minnesota and the Mississippi and Ohio River valleys.
  
  
• Transmission: Blastomycosis is usually acquired through the inhalation of airborne fungal spores released when contaminated soil, decaying vegetation, or other organic material is disturbed. Rarely, primary cutaneous infection may result from direct traumatic inoculation. Person-to-person transmission does not occur.
  
  
• Exposure history: Residence in or travel to endemic areas and exposure to soil, decaying wood, vegetation, or waterways may increase the likelihood of infection. Recreational and occupational exposures associated with blastomycosis include hunting, camping, forestry work, excavation, construction, landscaping, and other activities involving soil disturbance
  
  
• Clinical presentation: Symptoms usually develop between three weeks to three months following exposure. Common symptom include fever, cough, extreme tiredness, night sweats, muscle aches, and joint pain. Disease severity ranges from mild respiratory illness to severe pneumonia, acute respiratory distress syndrome, and life-threatening infection requiring hospitalization. Although pulmonary disease is the most common presentation, extrapulmonary dissemination to the skin, bones, central nervous system, and other organs can occur, particularly in patients with severe disease or immunocompromising conditions. Blastomycosis can occur in otherwise healthy individuals.
  
  
• Risk factors: Blastomycosis can occur in individuals of any age and in both immunocompetent and immunocompromised hosts; however, severe disease is more likely in people with immunocompromising conditions, underlying chronic medical conditions, and those at the extremes of age.