Rickettsia species

Rickettsia species is a topic covered in the Johns Hopkins ABX Guide.

To view the entire topic, please or .

Official website of the Johns Hopkins Antibiotic (ABX), HIV, Diabetes, and Psychiatry Guides, powered by Unbound Medicine. Johns Hopkins Guide App for iOS, iPhone, iPad, and Android included. Explore these free sample topics:

-- The first section of this topic is shown below --

MICROBIOLOGY

  • Obligate intracellular, small Gram-negative rod; genus Rickettsia
    • An expanding number of species cause human infection.
    • Transmitted by a variety of hematophagous arthropods: ticks, mites, lice, chiggers, fleas.
      • Most Rickettsia spp. have a geographic distribution.
      • R. typhi (murine or endemic typhus), worldwide.
    • Divided into the spotted fever group (SFG) and typhus group (TG).
  • Organisms infect endothelial cells, whose dysfunction leads to severe manifestations of the disease.
  • Rickettsial species and associated arthropod vectors: list continues to grow, >15 known species causing human infection (number below by no means complete).
    • Spotted Fever Group Rickettsia (SPGR):
      • North American species of interest:
        • R. rickettsii (Rocky Mt spotted fever, RMSF): tick, Western hemisphere (Dermacentor spp., dog and wood ticks and others).
        • R. parkeri (American Boutonneuse fever): Gulf Coast tick (Amblyomma maculatum) or Lone Star tick (A. americanum).
          • Febrile illness often with an eschar at the site of the tick bite.
        • R. philipiii (previously known as Rickettsial spp. 364D): transmitted by Dermacentor occidentalis (Pacific Coast tick)
          • Cases to date only describe in California but tick vector ranges the West Coast.
      • Worldwide: list not comprehensive, consider in returning travelers to the U.S.
        • R. akari (Rickettsialpox): mite (Lioponyssoides sanguineus, ectoparasite of house mice)
          • Seen in the U.S. and former states of the USSR.
          • Urban disease
          • Closely related, but no longer considered part of the SFGR.
        • R. australis (Australian tick typhus): I. holochyclus and I. tasmani host but only I. holochyclus aka the Australian paralysis tick, believed to frequently bite humans.
        • R. felis: flea-borne spotted fever
          • Increasingly common and described in the Americas, Europe, Africa, SE Asia and Australia.
        • R. conorii (Mediterranean spotted fever, MSF): dog tick (Rhipicephalus and Haemaphysalis genera)
          • Seen most commonly in the Mediterranean, India, Asia (Southwest) and Africa.
          • Subspecies:
            • R. conorii conorii: MSF
            • R. conorii caspia: endemic in Astrakhan region near Caspian sea
            • R. conorii indica: endemic in India, eschar rare
            • R. conorii isrealensis: eschar less frequent than MSF.
        • R. africae (African tick-bite fever): ticks (Amblyomma hebraeum, A. variegatum)
          • Mostly Southern Africa.
          • Most common rickettsial infection seen in travelers to Africa.
        • R. japonica (oriental spotted fever): At least six tick species implicated.
          • Japan
        • R. raoulti: dog tick (Dermacentor reticulatus)
          • Described in Europe, Eastern Europe.
          • May cause SENLAT syndrome (scalp eschar, neck lymphadenopathy after tick bite)
        • R. sibirica (Siberian tick typhus, North Asian tick typhus): multiple tick vectors
          • Siberia, Northern China, Mongolia
        • R. slovaca: transmitted by dog ticks, Dermacentor spp.
          • Associated with tick-borne lymphadenopathy (TIBOLA)
    • Typhus Group:
      • R. prowazekii (epidemic typhus): lice-transmitted.
        • Body louse (Pediculus humanus var. corporis)
        • Worldwide
        • Also, occasionally transmitted in North America by flying squirrel (Glaucomys volans)
          • Sporadic, 39 cases in the US (1976-2001)
      • R. typhi (murine/endemic typhus): global distribution, transmitted by fleas.
        • Rat flea (Xenopsylla cheopsis) and cat flea (Ctenocephalides felis).
        • Usually tropical, subtropical in distribution.
    • Scrub Typhus Group: reclassified from Rickettsia to Orientia.
      • Orientia tsutsugamushi (formerly R. tsutsugamushi, Tsutsugamushi disease, aka scrub typhus): transmitted by chiggers
        • Southeast Asia.
        • Can be a severe illness, similar to RMSF.
  • Rickettsial susceptibility testing not routinely performed given the difficulty of culture.
    • The reference standard is the dilution method using a plaque assay system (cell culture).

-- To view the remaining sections of this topic, please or --

MICROBIOLOGY

  • Obligate intracellular, small Gram-negative rod; genus Rickettsia
    • An expanding number of species cause human infection.
    • Transmitted by a variety of hematophagous arthropods: ticks, mites, lice, chiggers, fleas.
      • Most Rickettsia spp. have a geographic distribution.
      • R. typhi (murine or endemic typhus), worldwide.
    • Divided into the spotted fever group (SFG) and typhus group (TG).
  • Organisms infect endothelial cells, whose dysfunction leads to severe manifestations of the disease.
  • Rickettsial species and associated arthropod vectors: list continues to grow, >15 known species causing human infection (number below by no means complete).
    • Spotted Fever Group Rickettsia (SPGR):
      • North American species of interest:
        • R. rickettsii (Rocky Mt spotted fever, RMSF): tick, Western hemisphere (Dermacentor spp., dog and wood ticks and others).
        • R. parkeri (American Boutonneuse fever): Gulf Coast tick (Amblyomma maculatum) or Lone Star tick (A. americanum).
          • Febrile illness often with an eschar at the site of the tick bite.
        • R. philipiii (previously known as Rickettsial spp. 364D): transmitted by Dermacentor occidentalis (Pacific Coast tick)
          • Cases to date only describe in California but tick vector ranges the West Coast.
      • Worldwide: list not comprehensive, consider in returning travelers to the U.S.
        • R. akari (Rickettsialpox): mite (Lioponyssoides sanguineus, ectoparasite of house mice)
          • Seen in the U.S. and former states of the USSR.
          • Urban disease
          • Closely related, but no longer considered part of the SFGR.
        • R. australis (Australian tick typhus): I. holochyclus and I. tasmani host but only I. holochyclus aka the Australian paralysis tick, believed to frequently bite humans.
        • R. felis: flea-borne spotted fever
          • Increasingly common and described in the Americas, Europe, Africa, SE Asia and Australia.
        • R. conorii (Mediterranean spotted fever, MSF): dog tick (Rhipicephalus and Haemaphysalis genera)
          • Seen most commonly in the Mediterranean, India, Asia (Southwest) and Africa.
          • Subspecies:
            • R. conorii conorii: MSF
            • R. conorii caspia: endemic in Astrakhan region near Caspian sea
            • R. conorii indica: endemic in India, eschar rare
            • R. conorii isrealensis: eschar less frequent than MSF.
        • R. africae (African tick-bite fever): ticks (Amblyomma hebraeum, A. variegatum)
          • Mostly Southern Africa.
          • Most common rickettsial infection seen in travelers to Africa.
        • R. japonica (oriental spotted fever): At least six tick species implicated.
          • Japan
        • R. raoulti: dog tick (Dermacentor reticulatus)
          • Described in Europe, Eastern Europe.
          • May cause SENLAT syndrome (scalp eschar, neck lymphadenopathy after tick bite)
        • R. sibirica (Siberian tick typhus, North Asian tick typhus): multiple tick vectors
          • Siberia, Northern China, Mongolia
        • R. slovaca: transmitted by dog ticks, Dermacentor spp.
          • Associated with tick-borne lymphadenopathy (TIBOLA)
    • Typhus Group:
      • R. prowazekii (epidemic typhus): lice-transmitted.
        • Body louse (Pediculus humanus var. corporis)
        • Worldwide
        • Also, occasionally transmitted in North America by flying squirrel (Glaucomys volans)
          • Sporadic, 39 cases in the US (1976-2001)
      • R. typhi (murine/endemic typhus): global distribution, transmitted by fleas.
        • Rat flea (Xenopsylla cheopsis) and cat flea (Ctenocephalides felis).
        • Usually tropical, subtropical in distribution.
    • Scrub Typhus Group: reclassified from Rickettsia to Orientia.
      • Orientia tsutsugamushi (formerly R. tsutsugamushi, Tsutsugamushi disease, aka scrub typhus): transmitted by chiggers
        • Southeast Asia.
        • Can be a severe illness, similar to RMSF.
  • Rickettsial susceptibility testing not routinely performed given the difficulty of culture.
    • The reference standard is the dilution method using a plaque assay system (cell culture).

There's more to see -- the rest of this entry is available only to subscribers.

Last updated: September 5, 2020