The a (alpha)Proteobacteria Obligate intracellular parasites: Ehrlichia.Tick-borne,ehrlichiosis Rickettsia.Arthropod-borne,spotted fevers R.prowazekii Epidemic typhus ·R.typhi Endemic murine typhus 。R.rickettsii Rocky Mountain Spotted Fever• Obligate intracellular parasites: • Ehrlichia. Tick-borne, ehrlichiosis • Rickettsia. Arthropod-borne, spotted fevers • R. prowazekii Epidemic typhus • R. typhi Endemic murine typhus • R. rickettsii Rocky Mountain Spotted Fever The  (alpha) Proteobacteria