Syphilis is caused by treponema pallidum, a small unicellular animal parasite.
This disease is caused by a microorganism known as the spirochaeta pallida or treponema pallidum of Schaudinn and Hoffmann.
Postmortem examination always shows that the treponema has wrought wide-spread damage in the brain.
Treponema Trep·o·ne·ma (trěp'ə-nē'mə)
A genus of anaerobic spirochetes including species that cause syphilis, pinta, and yaws.