What is Histoplasmosis?
Histoplasmosis is caused by the dimorphic fungus, Histoplasma. This fungus is commonly found in soil with high nitrogen content (contaminated with bird or bat droppings).
Both pets and humans can develop histoplasmosis upon inhaling the fungal spores aerosolized in contaminated dirt or dust. Once in the lungs, the mold transforms into a yeast. There an appropriate immune response can eliminate the fungus, or it can cause disease localized to the lungs or disseminate through the blood or lymphatics causing disease in many other organ systems. As a result of dissemination, chronic disease can be localized to essentially any organ.
Both cats and dogs are at risk, and even cats that never leave the house develop histoplasmosis, accounting for approximately 1/3 of the reported cases.
Estimated Areas with Histoplasmosis in the United States