TABLE 2.

Characteristics of known and potential tick-borne rickettsiae, 2005

Rickettsia sp.	Recognized or potential tick vector(s)	Yr of first identification in ticks	Disease (yr of first clinical description)	Yr of first microbiological documentation of human cases	Selected clinical and epidemiological characteristics
Confirmed pathogens
Rickettsia rickettsii	Dermacentor andersoni, Dermacentor variabilis, Rhipicepahlus sanguineus, Amblyomma cajennense, Amblyomma aureolatum	1906	Rocky Mountain spotted fever (1899)	1906a	The prototypical and most severe tick-borne spotted fever rickettsiosis. Case fatality ratio is 20 to 25% in untreated patients. Peak occurrence during spring and summer. Eschars rarely reported. Broadly distributed in the Western Hemisphere and associated with several species of tick vectors.
Rickettsia conorii subsp. conorii	Rhipicephalus sanguineus	1932	Mediterranean spotted fever (1910)	1932a	Disease occurs in urban (66%) and rural (33%) settings. Rash occurs in 97%. Cases generally sporadic. Single eschar. Case fatality ratio, approximately 2.5%.
Rickettsia conorii subsp. israelensis	Rhipicephalus sanguineus	1974	Israeli spotted fever (1940)	1971a	Compared to Mediterranean spotted fever, eschars are less frequent. Mild to severe illness.
Rickettsia sibirica subsp. sibirica	Dermacentor nuttalli, Dermacentor marginatus, Dermacentor silvarum, Haemaphysalis concinna	Unknown	Siberian tick typhus (1934)	1946a	Disease occurs in predominantly rural settings. Cases occur during spring and summer. Increasing reports of cases. Cases generally associated with rash (100%), eschar (77%), and lymphadenopathy.
	Dermacentor sinicus	1974	North Asian Tick typhus (1977)	1984a
Rickettsia australis	Ixodes holocyclus, Ixodes tasmani	1974	Queensland tick typhus (1946)	1946a	Disease occurs in predominantly rural settings. Cases occur from June to November. Vesicular rash (100%), eschar (65%), and lymphadenopathy (71%). Two fatal cases described.
Rickettsia japonica	Ixodes ovatus, Dermacentor taiwanensis, Haemaphysalis longicornis, Haemaphysalis flava	1996	Oriental or Japanese spotted fever (1984)	1985a	Disease occurs in predominantly rural settings. Agricultural activities, bamboo cutting. April to October. Eschar (91%) and rash (100%). May be severe. One fatal case reported.
Rickettsia conorii subsp. caspia	Rhipicephalus sanguineus, Rhipicephalus pumilio	1992	Astrakhan fever (1970s)	1991a	Disease occurs in predominantly rural settings. Associated with eschar (23%), maculopapular rash (94%), and conjunctivitis (34%).
Rickettsia africae	Amblyomma hebraeum, Amblyomma variegatum	1990	African tick bite fever (1934)	1992a	Disease occurs in predominantly rural settings and is associated in international travellers returning from safari, hunting, camping, or adventure races. Outbreaks and clustered cases common (74%). Symptoms include fever (88%), eschars (95%) which are often multiple (54%), maculopapular (49%) or vesicular (50%) rash, and lymphadenopathy (43%). No fatal cases reported.
Rickettsia honei	Aponomma hydrosauri, Amblyomma cajennense, Ixodes granulatus	1993	Flinders Island spotted fever (1991)	1992a	Disease occurs in predominantly rural settings. Peak in December and January. Symptoms include rash (85%), eschar (25%), and lymphadenopathy (55%).
Rickettsia Sibirica subsp. mongolitimonae	Hyalomma asiaticum, Hyalomma truncatum	1991	Lymphangitis associated rickettsiosis (1996)	1996a	Few cases described in southern France between March and July and South Africa. Symptoms include eschar (75%), rash (63%), and lymphangitis (25%).
Rickettsia slovaca	Dermacentor marginatus, Dermacentor reticulatus	1968	Tick-borne lymphadenopathy (1997), Dermacentor-borne necrosis and lymphadenopathy (1997)	1997b, 2003a	Fever and rash rare. Typical eschar on the scalp with cervical lymphadenopathy. Illness mild.
Rickettsia heilongjiangensis	Dermacentor silvarum	1982	Far Eastern spotted fever (1992)	1992, 1996a	Rash, eschar, and lymphadenopathy. No fatal cases reported.
Rickettsia aeschlimannii	Hyalomma marginatum marginatum, Hyalomma marginatum rufipes, Rhipicephalus appendiculatus	1997	Unnamed (2002)	2002b,d	Few cases described in patients from Morocco and South Africa. Symptoms include eschar and maculopapular rash.
Rickettsia parkeri	Amblyomma maculatum, Amblyomma americanum, Amblyomma triste	1939	Unnamed (2004)	2004a	One case reported in a patient in the United States. Symptoms include fever, multiple eschars, and rash.
Rickettsia massiliae	Rhipicephalus sanguineus, Rhipicephalus turanicus, Rhipicephalus muhsamae Rhipicephalus lunulatus, Rhipicephalus sulcatus	1992	Unnamed (2005)	2005a	The strain was obtained from a blood of a patient from Sicily in 1985, stored, and definitively identified in 2005.
“Rickettsia marmionii”	Haemaphysalis novaeguineae	2003-2005	Australian spotted fever (2005)	2003-2005	Between February and June, six confirmed cases, including one with escar and two with a maculopapular rash.
Potential pathogens
Rickettsia conorii subsp. indica	Rhipicephalus sanguineus	1950	Indian tick typhus	2001b	Compared to Mediterranean spotted fever, rash usually purpuric. Eschar rarely found. Mild to severe.
Rickettsia canadensis	Haemaphysalis leporispalustris	1967			Possible Rocky Mountain spotted fever-like disease descibed in California and Texas. Suspected cause of acute cerebral vasculitis in Ohio.
Rickettsia amblyommii	Amblyomma americanum, Amblyomma cajennense, Amblyomma coelebs	1974	Unnamed (1993)	1993d	Possible cause of mild spotted fever rickettsiosis in the United States. Rickettsiae also recently identified in Brazilian ticks.
Rickettsia texiana	A. americanum	1943	Bullis fever (1942)	1943c	Possible agent of an epidemic which occurred among army personnel at Camp Bullis, Texas during 1942-1943.
Rickettsia helvetica	Ixodes ricinus, Ixodes ovatus, Ixodes persulcatus, Ixodes monospinus	1979	Unnamed (1999)	1999b	Although implicated in perimyocarditis and sarcoidosis, the validity of these associations has been debated or not accepted by rickettsiologists. Few cases documented by serology only in France and in Thailand. Rash and eschar seldom occur.

^aDocumentation by culture.

^bDocumentation by molecular tools.

^cDocumentation by animal or human inoculation.

^dDocumentation by serology.