Histoplasmosis

Histoplasmosis infection is usually asymptomatic or minimally symptomatic; however, infection with a large number of organisms or in people with immunodeficiency can result in severe, symptomatic pulmonary infection, which requires treatment.

Risk factors for more severe respiratory disease include inhalation of a large inoculum, impaired cellular immunity (e.g., AIDS/HIV infection, chronic immunosuppressive therapy), age <2 years, and chronic lung disease.

Endemic in temperate regions of the world including the Ohio, Mississippi, and Missouri River valleys in the US, southern Mexico, the Caribbean, and Central and South America. African histoplasmosis is a different clinical entity and is not covered in this topic.

The fungus proliferates well in soil contaminated with bird or bat droppings; therefore, exposure to Histoplasma capsulatum is commonly associated with cave exploration, close proximity to chicken roosts, demolition and excavation, and gathering wood.

Histoplasmosis is an infectious disease caused by the fungus Histoplasma capsulatum. It is not communicable from person to person but is acquired from inhalational exposure to infectious spores found in soil contaminated with bird or bat droppings. African histoplasmosis is a different clinical entity and will not be discussed here.