Types of Rickettsial Diseases
Rickettsia prowazekii causes louse-borne typhus, carried from person to person by two species of lice. Flea, or murine, typhus, caused by R. mooseri, is transmitted from rodents to people by fleas. Trench fever, caused by R. quintana, was an epidemic disease in World War I; it is transmitted by the rat flea from rat to person or from person to person. Trench fever disease reservoirs (perpetuation of the disease in wild animal populations) exist in some parts of E Europe, Mexico, and N Africa. Various typhuslike rickettsial diseases, such as Rocky Mountain spotted fever and African tick typhus, are transmitted by ticks from animal hosts to people. Mite-borne rickettsial infections include rickettsialpox, caused by Rickettsia akari and transmitted from house mice to people, and scrub typhus, or tsutsugamushi fever, caused by R. tsutsugamushi and found in Japan and SE Asia. Q fever, caused by Coxiella burnetii, a more hardy rickettsia viable outside the living host, is usually transmitted to humans by inhalation of contaminated airborne particles or from contaminated materials, often from infected livestock; it is an occupational hazard among dairy farm and slaughterhouse workers. A new rickettsia, Ehrlichia chaffeenis, which results in human ehrlichiosis, was identified in 1986.