Rocky Mountain spotted fever is the most severe and most frequently reported rickettsial illness in the United States, and has been diagnosed throughout the Americas. Some synonyms for Rocky Mountain spotted fever in other countries include "tick typhus", "Tobia fever" (Columbia), "São Paulo fever" and "fiebre maculosa" (Brazil), and "fiebre manchada" (Mexico). The disease is caused by Rickettsia rickettsii, a species of bacteria that is spread to humans by hard ticks (Ixodidae). ...

Human ehrlichiosis is a zoonotic infection in humans transmitted by a variety of tick species. The genus Ehrlichiae are characterized by small, rounded gram-negative cocci that invade white blood cells.It is quite similar to the rocky mountain spotted fever, but rash is not seen in patients.

Rocky Mountain Spotted Fever as related to Ehrlichiosis