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.

DiseaseAgentVectors
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
EhrlichiosisEhrlichiaeTick

Mnemonics to remember vectors and agents of rickettsial diseases

LET

Louse-borne

  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

TERM

Tick-borne

  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

MPS

Mite-borne

  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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