What is "histoplasma"

Histoplasma is a genus of dimorphic fungi commonly found in guano (the feces of birds and bats) and in soil where guano falls. In modern taxonomy, the genus contains a single species, Histoplasma capsulatum, that has several infraspecific varieties. The normal variety is the causative agent of classic histoplasmosis; Histoplasma capsulatum var. duboisii causes African histoplasmosis; and Histoplasma capsulatum var. farciminosum causes epizootic lymphangitis in horses. The duboisii and farciminosum varieties have each formerly been classified as separate species, Histoplasma duboisii and Histoplasma farciminosum.

Histoplasma capsulatum is "distributed worldwide, except in Antarctica, but most often associated with river valleys" and occurs chiefly in the " central and eastern United States" followed by " Central and South America, and other areas of the world" It is most prevalent in the Ohio and Mississippi river valleys. It was discovered by Samuel Taylor Darling in 1906.