Histoplasmosis is a disease caused by the fungus Histoplasma capsulatum, which grows in soil and other material contaminated with bat or bird droppings. Spores become airborne when the soil is disturbed, and you can become infected by inhaling them. The disease can’t be transmitted from person to person.
Anyone who lives in an area where H. capsulatum is common, such as the eastern and central United States, is at risk. In fact, the U.S. Centers for Disease Control and Prevention says that as many as 80% of all the people who live in these areas can develop a positive skin test for histoplasmosis, although most of those infected never get sick. When symptoms do develop, they primarily affect the lungs and respiratory system and may include malaise, fever, chest pains, and a dry (nonproductive) cough. If symptoms do occur, they generally begin about 10 days after exposure.
When other organs are affected, the disease is called disseminated histoplasmosis, which can be life-threatening if left untreated. At greatest risk are infants, young children, and older persons, particularly those with chronic lung disease. Disseminated histoplasmosis is more frequently seen in people with cancer, AIDS or those whose immune function is suppressed for any reason.
The usual treatment for histoplasmosis is anti-fungal drugs. I checked with Randy Horwitz, M.D., medical director of the Arizona Center for Integrative Medicine, about the safety of amphotericin B for disseminated histoplasmosis. He told me that intravenous amphotericin B is the initial drug of choice for patients with severe disease. Because the drug can be very toxic to the kidneys and liver, Dr. Horwitz emphasized that the function of these organs needs to be monitored with regular blood tests during treatment. As soon as feasible, patients should be switched to a less toxic oral drug, such as itraconazole.
While Dr. Horwitz acknowledged that amphotericin B has more side effects than many other antibiotics, he said its toxicity can be minimized by using a special, liposomal formulation, in which the drug is encased in a sort of "bubble." While this is a more expensive mode of treatment, it lessens adverse effects (unfortunately, not in everyone). There are no appropriate alternative therapies for severe or disseminated histoplasmosis.
If you live in an area where H. capsulatum is common, do make an effort to avoid exposure to it, which is most likely to happen in poultry houses, caves, other areas harboring bats, and near bird roosts.
Andrew Weil, M.D.