Mycoses (diseases caused by fungi) include several respiratory infections resulting from inhalation of viable spores of opportunistic pathogens that usually grow in soil. Usually, the host is immunocompromised, or in some cases is exposed to very high levels of airborne spores.
For example, Histoplasma capsulatum, the cause of histoplasmosis, is particularly common in areas contaminated with chicken or bat feces. The fungal growth develops inside the lung, in a fashion comparable to the tubercles formed during tuberculosis. Histoplasmosis is endemic in parts of the midwestern United States.
A similar lung disease known as San Joaquin Valley fever, caused by Coccidioides immitis, is seen more commonly in the southwestern regions of the United States. This fungus lives in desert soils, and in some localities the levels of asymptomatic infection may be as high as 80%.
Several species of Aspergillus can also cause a lung infection known as aspergillosis. A. fumigatus has been of particular concern around some sludge and yard waste composting sites, where it can apparently grow on woodchips, leaves, and other cellulosic materials. It can tolerate higher temperatures (50°C) than can most other fungi. However, the actual incidence of disease seems to be very low (few or no cases per year), although allergic reactions are more common.
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