Classification: ICD-9 115; ICD-10 B39.0-B39.4, B39.9
Synonyms: Cave disease, Ohio valley disease, reticuloendotheliosis, African histoplasmosis.
Agent: The dimorphic fungi: Histoplasma capsulatum (worldwide) and H. capsulatum var. duboisii (Africa). The fungi grow as a mycelium in the soil at ambient temperatures and convert to the yeast form in the lung at body temperature.
Reservoir: Soil with high nitrogen content, particularly areas with a lot of bird or bat guano, like barns and caves. Blackbird roosts can also be heavily contaminated. Unlike bats, birds are not infected by H. capsulatum and do not excrete the fungus in their droppings. Bird droppings are considered a nutrient source for fungal growth in the already contaminated soil.
Transmission: Through inhalation of aerosolized microconidia from disturbed soil or guano. Also by inoculation and organ transplantation.
Cycle: The fungus grows as a mycelium in the environment and in human or animal tissue it converts into a budding yeast.
Incubation period: 3 to 17 days; average 10 days.
Clinical findings
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