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Information for Healthcare Professionals about Blastomycosis

Clinical features

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

Etiologic agent

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

Reservoir and endemic areas

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

Transmission

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

Sequelae

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

Diagnosis

  • 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.

Treatment

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

Risk groups

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

Surveillance and statistics

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.

References

  1. 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 Wisconsin. N Engl J Med. 1986 Feb 27;314(9):529-34.
  2. Saccente M, Woods GL. Clinical and laboratory update on blastomycosis. Clin Microbiol Rev. 2010 Apr;23(2):367-81.
  3. Baumgardner DJ, Halsmer SE, Egan G. Symptoms of pulmonary blastomycosis: northern Wisconsin, United States. Wilderness Environ Med. 2004 Winter;15(4):250-6.
  4. 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 dermatitidis. PLoS One. 2013;8(3):e59237.
  5. 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, 1960–1967. Am J Epidemiol. 1970;92(2):121–31.
  6. Bradsher RW, Chapman SW, Pappas PG. Blastomycosis.  Infect Dis Clin North Am. 2003;17(1) 21-40, vii.
  7. Morris SK, Brophy J, Richardson SE, Summerbell R, Parkin PC, Jamieson F, et al. Blastomycosis in Ontario, 1994-2003. Emerg Infect Dis. 2006 Feb;12(2):274-9.
  8. Litvinov IV, St-Germain G, Pelletier R, Paradis M, Sheppard DC. Endemic human blastomycosis in Quebec, Canada, 1988-2011. Epidemiol Infect. 2013 Jun;141(6):1143-7.
  9. Fanella S1, Skinner S, Trepman E, Embil JM. Blastomycosis in children and adolescents: a 30-year experience from Manitoba. Med Mycol. 2011 Aug;49(6):627-32.
  10. Cheikh Rouhou S, Racil H, Ismail O, Trabelsi S, Zarrouk M, Chaouch N, et al. Pulmonary blastomycosis: a case from Africa. ScientificWorldJournal. 2008 Nov 2;8:1098-103.
  11. Chakrabarti A, Slavin MA. Endemic fungal infections in the Asia-Pacific region. Med Mycol. 2011 May;49(4):337-44.
  12. Gray NA, Baddour LM. Cutaneous inoculation blastomycosis. Clin Infect Dis. 2002 May 15;34(10):E44-9.
  13. 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 America. Clin Infect Dis. 2008 Jun 15;46(12):1801-12.
  14. Pappas PG, Threlkeld MG, Bedsole GD, Cleveland KO, Gelfand MS, Dismukes WE. Blastomycosis in immunocompromised patients. Medicine. 1993 Sep;72(5):311-25.
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