Rickettsial Diseases Mnemonic

rickettsial disease

Rickettsia is a gram negative obligate intracellular parasite. As shown in the table above, human is only an incidental host except in louse-borne epidemic typhus.

Typhus groupEpidemic typhus or Brill Zinsser diseaseR. prowazekiiLouse
Murine/Endemic typhusR.typhi (R.mooseri)Flea
Spotted fever groupRocky mountain spotted feverR.rickettsiiTick
R. poxR.akariMite
Fever boutonneuse or Mediterranean spotted fever or Indian tick typhusR.conoriiTick
OtherQ. feverCoxiella burnettiiNil (Air borne)
Trench fever / Five day feverRochalimaea Quintana (Bartonella Quintana)Louse
Scrub typhus (Chigger borne typhus)Rickettsia or Orientia tsutsugambushiMite

Mnemonics to remember vectors and agents of rickettsial diseases



  1. Epidemic typhus
  2. Trench fever

Take the 2nd letter from these. The name of the agent starts with the same letter.

  • ePidemic typhus: Prowazekii (R.prowazekii)
  • tRench fever: Rochalimaea quintana



  1. Ehrlichiosis
  2. Rocky mountain spotted fever
  3. Mediterranean spotted fever

Take the 1st letter from these. The name of the agent starts with the same letter.

  • Ehrlichiosis: Ehrlichia chaffeensis
  • Rocky mountain spotted fever: R. Rickettsii
  • Mediterranean spotted fever (exception): R.conorii



  1. Pox (R.pox) – R.akari
  2. Scrub typhus – Orientia tsutsugambushi

At last, Endemic typhus is flea borne and caused by R.typhi.

Weil-Felix reaction

It is a heterophile agglutination test based on sharing of alkali stable polysaccharide between typhus rickettsia and some strain of Proteus bacilli (OX 19, OX – 2, OX K).

Weil-Felix reaction
OX-19 (+++): In Epidemic and Endemic typhus

OX 19, OX-2 (++): In Rocky Mountain Spotted fever

OX-K (+++): In Scrub typhus

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