General Information: Causative agent for Rocky Mountain Spotted Fever. This organism was first identified by Dr. Howard Rickets as the causative agent of Rocky Mountain Spotted Fever, which was originally named for its geographic distribution at the time, it is now known to be widespread throughout the North American continent. This bacterium is an obligate intracellular pathogen that infects primarily the vascular endothelium, and occasionally smooth muscle tissue. It is passed to the human host from a tick bite, and the tick acts as both a natural reservoir and a vector for disease transmission. Once the organism is endocytosed by the host cell, it quickly escapes the phagozome, and replicates intracellularly, causing cell death and tissue damage. The disease is characterized by a spotted rash and has a high mortality rate if left untreated.