Caused by R. rickettsii, RMSF has the highest case-fatality rate of all rickettsial diseases.

  • In the United States, the prevalence is highest in the south-central and southeastern states. Most cases occur between May and September.
  • A rare presentation of fulminant RMSF is seen most often in male black pts with G6PD deficiency.
  • RMSF is transmitted by different ticks in different geographic areas— e.g., the American dog tick (Dermacentor variabilis) transmits RMSF in the eastern two-thirds of the United States and in California, and the Rocky Mountain wood tick (D. andersoni) transmits RMSF in the western U.S.


Rickettsiae are inoculated by the tick after ≥6 h of feeding, spread lymphohematogenously, and infect numerous foci of contiguous endothelial cells.  Increased vascular permeability, with edema, hypovolemia, and ischemia, causes tissue and organ injury.


The incubation period is ~1 week (range, 2–14 days). After 3 days of nonspecific symptoms, half of pts have a rash characterized by macules appearing on the wrists and ankles and subsequently spread

  • Lesions ultimately become petechial in 41–59% of pts, appearing on or after day 6 of illness in ~74% of all cases that include a rash. The palms and soles become involved after day 5 in 43% of pts but do not become involved at all in 18–64%.
  • Patients may develop hypovolemia, prerenal azotemia, hypotension, noncardiogenic pulmonary edema, renal failure, hepatic injury, and cardiac involvement with dysrhythmias. Bleeding is a rare but potentially lifethreatening consequence of severe vascular damage.
  • CNS involvement—manifesting as encephalitis, focal neurologic deficits, or meningoencephalitis—is an important determinant of outcome. In meningoencephalitis, CSF is notable for pleocytosis with a mononuclear cell or neutrophil predominance, increased protein levels, and normal glucose levels.
  • Laboratory findings may include increased plasma levels of acute-phase reactants such as C-reactive protein, hypoalbuminemia, hyponatremia, and elevated levels of creatine.


Without treatment, the pt usually dies in 8–15 days; fulminant RMSF can result in death within 5 days. The mortality rate is 3–5% despite the availability of effective antibiotics, mostly because of delayed diagnosis. Survivors of RMSF usually return to their previous state of health.


The medicines that can be thought of use are:-

  • Aconite
  • Belladonna
  • Bryonia
  • Gelsemium
  • Sulphur.