Histoplasmosis is caused by Histoplasma, a fungus that lives in the environment, especially in soil contaminated with bat or bird droppings. When contaminated soil is disturbed, spores become airborne and can be inhaled. The spores cannot, however, be transmitted from one infected person to another. Found throughout the world, the fungus is endemic in some areas of the United States, primarily the Mississippi and Ohio River Valleys. It has been found in bird roosts, poultry house litter, caves, and areas where bats live.
In most cases, infection does not cause any symptoms. If symptoms do occur, they will appear between 3 and 17 days after exposure. If acute respiratory illness occurs, it results in fever, chest pains, a dry cough, and an overall feeling of illness. When organs other than the lungs are affected, the disease is called disseminated histoplasmosis, a form that can be fatal if not treated. People with AIDS, cancer, or immune systems compromised by other illnesses are at the highest risk for this form of the disease.
Mild forms of the disease rarely require treatment. In cases of acute histoplasmosis and in all cases of chronic and disseminated disease, antifungal medications are used, with the strongest varieties administered intravenously. Depending on the severity of the infection and the status of the individual’s immune system, treatment can last from 3 months to 1 year. If re-infected, past infection typically provides partial protection from symptoms.
The best way to prevent the disease is to avoid places that might harbor the fungus, such as locations with accumulations of bat or bird droppings. It is also important to avoid activities associated with getting histoplasmosis. These include digging in soil or chopping wood where bird or bat droppings are found; cleaning chicken coops; exploring caves; and cleaning, remodeling, or tearing down old buildings. If you must work in areas where the fungus might be present, consult the National Institute for Occupational Safety and Health’s publication Histoplasmosis—Protecting Workers at Risk for safety precautions.