What is Histoplasmosis?

Histoplasmosis is a disease caused by the fungus Histoplasma. Histoplasma is a thermally-dimorphic fungus meaning it grows as a thread-like mould in the environment and as a yeast (a single-celled fungus) when it causes human infections. The fungus is commonly found in the environment particularly in soil that contains bird or bat droppings. People can get this disease by inhaling spores of this fungus from the air usually during outdoor activities that involve disturbing the soil. Most healthy individuals will not get sick and will get better on their own without any medication. Other people may get sick depending on the number of spores inhaled and their immune system. These people may experience fever, cough and fatigue requiring medical treatment.

If a person has a weakened immune system, then severe infection can occur if the infection spreads from the lungs to other organs. In order to confirm the diagnosis of histoplasmosis, specimens from a patient (e.g. blood, sputum) is sent to a laboratory for culture and/or histology. Culture involves plating the specimen out onto appropriate growth media and observing mould growth within at least four weeks. Histology involves direct visualisation of Histoplasma yeast cells in infected tissues. Treatment of histoplasmosis requires prescription antifungal medicines such as amphotericin B followed by itraconazole.