Information for Healthcare Professionals about Blastomycosis
Asymptomatic in approximately 50% of cases.1 Symptomatic persons usually present 3 weeks to 3 months after exposure. The clinical presentation of acute pulmonary blastomycosis is often non-specific; symptoms may include: fever, cough, night sweats, myalgias, arthalgias, anorexia, chest pain, and fatigue.2,3
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): Blastomyces PCR can be used to confirm culture or histopathologic identification and on blood to detect disseminated disease.
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 Blastomycosisexternal icon
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
- Klein BS, Vergeront JM, Weeks RJ, Kumar UN, Mathai G, Varkey B, et al. Isolation of Blastomyces dermatitidis in soil associated with a large outbreak of blastomycosis in Wisconsinexternal icon. N Engl J Med. 1986 Feb 27;314(9):529-34.
- Saccente M, Woods GL. Clinical and laboratory update on blastomycosisexternal icon. Clin Microbiol Rev. 2010 Apr;23(2):367-81.
- Baumgardner DJ, Halsmer SE, Egan G. Symptoms of pulmonary blastomycosis: northern Wisconsin, United Statesexternal icon. Wilderness Environ Med. 2004 Winter;15(4):250-6.
- Brown EM, McTaggart LR, Zhang SX, Low DE, Stevens DA, Richardson SE. Phylogenetic analysis reveals a cryptic species Blastomyces gilchristii, sp. nov. within the human pathogenic fungus Blastomyces dermatitidisexternal icon. PLoS One. 2013;8(3):e59237.
- Furcolow ML, Busey JF, Menges RW, Chick EW. Prevalence and incidence studies of human and canine blastomycosis. II. Yearly incidence studies in three selected states, 1960–1967external icon. Am J Epidemiol. 1970;92(2):121–31.
- Bradsher RW, Chapman SW, Pappas PG. Blastomycosisexternal icon. Infect Dis Clin North Am. 2003;17(1) 21-40, vii.
- Morris SK, Brophy J, Richardson SE, Summerbell R, Parkin PC, Jamieson F, et al. Blastomycosis in Ontario, 1994-2003external icon. Emerg Infect Dis. 2006 Feb;12(2):274-9.
- Litvinov IV, St-Germain G, Pelletier R, Paradis M, Sheppard DC. Endemic human blastomycosis in Quebec, Canada, 1988-2011external icon. Epidemiol Infect. 2013 Jun;141(6):1143-7.
- Fanella S, Skinner S, Trepman E, Embil JM. Blastomycosis in children and adolescents: a 30-year experience from Manitobaexternal icon. Med Mycol. 2011 Aug;49(6):627-32.
- Cheikh Rouhou S, Racil H, Ismail O, Trabelsi S, Zarrouk M, Chaouch N, et al. Pulmonary blastomycosis: a case from Africaexternal icon. ScientificWorldJournal. 2008 Nov 2;8:1098-103.
- Chakrabarti A, Slavin MA. Endemic fungal infections in the Asia-Pacific regionexternal icon. Med Mycol. 2011 May;49(4):337-44.
- Gray NA, Baddour LM. Cutaneous inoculation blastomycosisexternal icon. Clin Infect Dis. 2002 May 15;34(10):E44-9.
- Chapman SW, Dismukes WE, Proia LA, Bradsher RW, Pappas PG, Threlkeld MG, et al. Clinical practice guidelines for the management of blastomycosis: 2008 update by the Infectious Diseases Society of Americaexternal icon. Clin Infect Dis. 2008 Jun 15;46(12):1801-12.
- Pappas PG, Threlkeld MG, Bedsole GD, Cleveland KO, Gelfand MS, Dismukes WE. Blastomycosis in immunocompromised patientsexternal icon. Medicine. 1993 Sep;72(5):311-25.