Histoplasma is a genus of fungi in the order Onygenales.

They are the causative agents of histoplasmosis in humans and epizootic lymphangitis in horses.

[4][5] Infection occurs through inhalation of microconidia or small mycelial fragments.

The dimorphic mold-yeast transforms and enters host macrophages and proliferates within them.

[6] Species are mainly found in the Ohio and Mississippi River Valleys in the United States (H.ohiense and H. mississippiense) as well as Central (H. capsulatum) and South America (H. suramericanum), Africa (H. duboisii), Asia, and Australia.