European Journal of Epidemiology

, Volume 7, Issue 3, pp 237-245

First online:

Epidemiology of rickettsial diseases

  • D. H. WalkerAffiliated withDepartment of Pathology, The University of Texas Medical Branch at Galveston
  • , D. B. FishbeinAffiliated withCenters for Disease Control - Rickettsial and Epidemiology Sections, Viral and Rickettsial zoonoses Branch - Division of Viral and Rickettsial Disease - Center for Infections Disease

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Rickettsial diseases have a diversity of epidemiologic characteristics reflective of the variety of ecologic situations in which the obligate intracellular bacteria are transmitted to humans. For the spotted fever group (SFG) rickettsiae, Rickettsia typhi. R. tsutsugamushi, Coxiella burnetii, and the human ehrlichial agent, humans are a dead-end host who plays no role in the maintenance of the organism in nature. All rickettsioses exist as zoonoses. Moreover, all rickettsiae are found in infected arthopods, which generally serve as the natural hosts and can transmit the infection to the next generation of ticks, mites, chiggers, or fleas. From our anthropocentric viewpoint, Q fever aerosol infection from parturient animals and Brill-Zinsser disease ignited epidemics of louse-borne epidemic typhus are exceptions. However, silent cycles of C. burnetii in ticks and R. prowazekii in the flying squirrel flea may have maintained these agents in transovarial or enzootic cycles for eons before humans and their domestic animals arrived on the scene. Thus, the epidemiology of rickettsial diseases must be recognized as an unfortunate aberration of the rickettsial economy.

Several excellent reviews of rickettsial ecology contain a wealth of useful information (2, 8, 55, 70, 84).


Human ehrlichiosis Rickettsial spotted fevers Typhus fevers Scrub typhus Q fever Zoonosis