Can you tell me how rickettsia cause illness?

Inflammation: This is such an interesting question and I can't answer it in 400 words. Rickettsiae are gram negative bacteria, yet they cannot live outside of a cell. They are energy parasites. Since they are "other" they are attacked by the immune cells leading to inflammation which leads to fever and manifestations of disease such as typhus, RMSF, ehrlichiosis. If this answers your question, or we converse.