Rickettsial diseases.

The rickettsioses have several unifying features. Arthropod vectors are the common means of transmission. Fever, headache, myalgias, and the characteristic eruption (except in Q fever and ehrlichioses) are the hallmarks of the clinical presentation. The diseases share a common pathogenesis, namely, vasculitis, and treatment uniformly consists of tetracycline or chloramphenicol. Distinguishing aspects of these processes include the multitude of different reservoirs, the progression of the rash, and the nonspecific antigen test (Weil-Felix) results.