Infectious Disease Book

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Rocky Mountain Spotted FeverAka: Rickettsia rickettsii

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  1. See Also
    1. Vector Borne Disease
    2. Prevention of Tick-borne Infection
    3. Tick Removal
  2. Pathophysiology
    1. Transmission
      1. Person to person transmission does not occur
      2. Tick bite
        1. Wood tick is vector in Western U.S.
        2. Dog tick is vector in Southern and Eastern U.S.
    2. Infects blood vessel walls
      1. Endothelial cells
      2. Smooth muscle cells
    3. Rickettsia rickettsii is causative organism
      1. Small pleomorphic organism
      2. Obligate intracellular parasite
  3. Epidemiology
    1. Bimodal age distribution
      1. Ages 5 to 9 years old (most common age affected)
      2. Age over 60 years old
    2. Endemic area (only occurs in Western Hemisphere)
      1. North America
        1. Occurs in all states except Maine, Hawaii, Alaska
        2. Atlantic coast states (most common)
        3. Midwest
      2. Central America
      3. South America
    3. Timing
      1. Most common April to September
  4. Symptoms (follows 5-7 day incubation)
    1. Fever
    2. Frontal Headache
    3. Myalgias (back and leg muscles)
    4. Malaise
    5. Nausea or Vomiting
  5. Signs: Rash (occurs in 90% of patients)
    1. Onset in first week of illness
    2. Characteristics
      1. Initial: Pink blanching Macules 1 to 4 mm in diameter
      2. Later: Macules transition to Papules and Petechiae
      3. Final: Coalesce into large Ecchymoses and Ulcerations
    3. Distribution
      1. Onset: Wrists, palms, forearms, ankles and soles
      2. Later: Trunk, axilla, buttocks, neck and face
  6. Diagnosis
    1. Based on clinical findings
    2. Specific testing is for confirmation only
      1. Skin biopsy with immunofluorescent Rickettsia stain
      2. Rickettsia Serology
  7. Labs
    1. Complete Blood Count
      1. White Blood Cell count normal or slightly decreased
      2. Thrombocytopenia
    2. Liver transaminases increased
      1. Aspartate Aminotransferase (AST)
      2. Alanine Aminotransferase (ALT)
    3. Serum Sodium
      1. Hyponatremia
    4. Cerebrospinal Fluid
      1. CSF Pleocytosis with monocytic predominance
    5. Skin biopsy with immunofluorescent stain for Rickettsia
      1. Used for confirmation, not for diagnosis
      2. Test Sensitivity: 60%
      3. Test Specificity: Very high
    6. Rickettsia Serology
      1. Positive 7 to 10 days after symptom onset
      2. Used for confirmation, not for diagnosis
  8. Management
    1. Start treatment immediately when diagnosis suspected
      1. Do not delay treatment for diagnostic testing
    2. Antibiotic Course
      1. Minimum course: 5 to 7 days
      2. Continue antibiotics until afebrile for 2 days
    3. Antibiotics
      1. Doxycycline or Tetracycline or
      2. Chloramphenicol
  9. Complications
    1. Encephalitis
    2. Noncardiac pulmonary edema
    3. Acute Respiratory Distress Syndrome (ARDS)
    4. Cardiac arrhythmia
    5. Coagulopathy
    6. Gastrointestinal Bleeding
    7. Skin Necrosis
  10. Prognosis
    1. Untreated: 25% Mortality within 8 to 15 days
    2. Treated: 5% Mortality
    3. G6PD is associated with complications and poor outcome
  11. Prevention
    1. See Prevention of Vector-borne Infection
  12. Resources
    1. CDC Rocky Mountain Spotted Fever
      1. http://www.cdc.gov/ncidod/dvrd/rmsf
  13. References
    1. Thorner (1998) Clin Infect Dis 27:1353

Rickettsia rickettsii antigen (C0369943)

ConceptsImmunologic Factor (T129)
EnglishRickettsia rickettsii, Rickettsia rickettsii Ag, Rickettsia rickettsii antigen
Spanishantígeno de Rickettsia rickettsii, antigeno de Rickettsia rickettsii
CreditsDerived from the NIH UMLS (Unified Medical Language System)



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