Information for Healthcare Professionals about Blastomycosis

Blastomycosis is caused by the dimorphic fungus Blastomyces dermatitidis. Recent phylogenetic analysis suggests that B. dermatitidis may comprise two species, B. dermatitidis and B. gilchristii.⁴

Soil and decaying organic matter such as wood or leaves. Endemic areas in the US include the midwestern, south-central, and southeastern states, particularly areas surrounding the Ohio and Mississippi River valleys, the Great Lakes, and the Saint Lawrence River.^5,6 Parts of Canada are also endemic, particularly Ontario,⁷ Quebec,⁸ and Manitoba.⁹ Autochthonous cases have also been reported from Africa¹⁰ and India.¹¹

Blastomycosis is typically acquired via inhalation of airborne conidia. Primary cutaneous blastomycosis is uncommon but can result from traumatic inoculation.¹²

Acute pulmonary blastomycosis can progress to acute respiratory distress syndrome (ARDS). Approximately 25 to 40% of symptomatic cases will develop extrapulmonary infection, which typically manifests as cutaneous, osteoarticular, genitourinary, or central nervous system disease.¹³

• Antigen detection: Enzyme immunoassay (EIA) is typically performed on urine or serum, but can also be used on bronchoalveolar lavage fluid. Cross-reactions can occur with histoplasmosis and other fungal diseases.
• Antibody tests: antibody tests such as immunodiffusion (ID) and complement fixation (CF) are available, but have low sensitivity and specificity.
• Culture: the gold standard for diagnosing blastomycosis. A commercially available DNA probe (AccuProbe, GenProbe Inc.) can be used to confirm.
• Microscopy: important for detection of yeast in tissue or respiratory secretions.
• Polymerase chain reaction (PCR): PCR for detection of Blastomyces directly from clinical specimens is still experimental, but promising.

Amphotericin B is recommended for moderate to severe disease, central nervous system disease, immunosuppressed patients, or pregnant patients. Itraconazole is recommended for mild to moderate disease and step-down therapy. For more detailed treatment guidelines, please refer to the Infectious Diseases Society of America’s Clinical Practice Guidelines for the Management of Blastomycosis

People in endemic areas, particularly those who have occupations or participate in activities that expose them to soil. Immunocompromised persons may be at higher risk for developing severe forms of the disease.¹⁴

Blastomycosis is reportable in the following states: Arkansas, Louisiana, Michigan, Minnesota, and Wisconsin. Check with your local, state, or territorial public health department for more information about disease reporting requirements and procedures in your area. Click here for blastomycosis statistics.