http://en.wikipedia.org/wiki/Rickettsia

Rickettsia species are carried by many chiggers, ticks, fleas, and lice, and cause diseases in humans such as typhus, rickettsialpox, Boutonneuse fever, African tick bite fever, Rocky Mountain spotted fever, Flinders Island spotted fever and Queensland tick typhus (Australian tick typhus).[10] They have also been associated with a range of plant diseases. The name rickettsia is often used for any member of the Rickettsiales.