Rocky Mountain spotted fever

Last Updated: 2023-07-07

Author(s): Anzengruber F., Navarini A.

ICD11: 1C31.0

American rock mountain fever, new world tick-bite fever.

Rickettsiosis caused by Rickettsia rickettsii.

  • Widespread worldwide.
  • Mostly in the Americas (especially during the spring or summer months).
  • Mostly affecting children between 4-10 yrs.

  • Pathogen: Rickettsia rickettsii, Rickettsia rickettsii is transmitted by tick bites.

  • Incubation period: 2-14 days.
  • At the site of inoculation, a partly ulcerated, possibly crusted papule appears.
  • Maculopapular exanthema (initially on wrists and ankles).
  • Nosebleed, fever, splenohepatomegaly.
  • There may be involvement of kidney, liver and CNS.

  • Travel history.
  • Clinical.
  • Lice infestation.
  • BB, liver and kidney values, electrolytes.
  • From the 2nd week of illness Weil-Felix reaction (agglutination test).
  • From the 3rd week of illness, complement fixation reaction. 
  • From the 3rd week of illness, indirect immunofluorescence test.

Lethality: 5–25%.

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  2. Elghetany, M.T. and D.H. Walker, Hemostatic Changes in Rocky Mountain Spotted Fever and Mediterranean Spotted Fever. American Journal of Clinical Pathology, 1999. 112(2): p. 159-168.
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