[ ri-ket-see-uh ]

noun,plural rick·ett·si·ae [ri-ket-see-ee], /rɪˈkɛt siˌi/, rick·ett·si·as [ri-ket-see-uhz]. /rɪˈkɛt si əz/.
  1. any member of the genus Rickettsia, comprising rod-shaped to coccoid microorganisms that resemble bacteria but can be as small as a large virus and reproduce only inside a living cell, parasitic in fleas, ticks, lice, and mites and transmitted by bite to vertebrate hosts, including humans, causing such severe diseases as typhus and Rocky Mountain spotted fever.

  2. any rickettsia or rickettsialike microorganism of the orders Rickettsiales and Chlamydiales.

Origin of rickettsia

1915–20; <New Latin, after Howard T. Ricketts (1871–1910), U.S. pathologist; see -ia

Other words from rickettsia

  • rick·ett·si·al, adjective

Words Nearby rickettsia

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

British Dictionary definitions for rickettsia


/ (rɪˈkɛtsɪə) /

nounplural -siae (-sɪˌiː) or -sias
  1. any of a group of parasitic bacteria that live in the tissues of ticks, mites, and other arthropods, and cause disease when transmitted to man and other animals

Origin of rickettsia

C20: named after Howard T. Ricketts (1871–1910), US pathologist

Derived forms of rickettsia

  • rickettsial, adjective

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