Infectious Disease Book


Rocky Mountain Spotted Fever

Aka: Rocky Mountain Spotted Fever, Rickettsia rickettsii
  1. See Also
    1. Tick-Borne Disease
    2. Vector Borne Disease
    3. Prevention of Tick-borne Infection
    4. Tick Removal
  2. Epidemiology
    1. Rocky Mountain Spotted Fever is the most common Rickettsial Disease in the United States
      1. Up to 6000 cases per year of RMSF and related Rickettsial spotted fevers (see below)
      2. RMSF is the most lethal of Tick Borne Illnesses (5-10% mortality)
    2. Bimodal age distribution
      1. Ages 5 to 9 years old (highest mortality)
      2. Age over 40-60 years old
    3. Timing
      1. Most common April to September (90% of cases)
    4. Endemic area (only occurs in Western Hemisphere)
      1. Central America
      2. South America
      3. North America
        1. Occurs in all states except Maine, Hawaii, Alaska
        2. Midwest
        3. Atlantic coast and south central states (account for 60% of cases in U.S.)
          1. North Carolina
          2. Oklahoma
          3. Arkansas
          4. Tennessee
          5. Missouri
    5. Other similar Rickettsial spotted fevers
      1. Respond to similar antibiotics as those used in Rocky Mountain Spotted Fever
      2. In U.S.
        1. Rickettsial Pox (R. akari in North America)
        2. American Boutonneuse fever (R. parkeri in southeast U.S.)
        3. Finders Island Spotted Fever (R. honei in northwest U.S. as well as Australia and southeast Asia)
      3. Non-U.S.
        1. Mediterranean Spotted Fever or Boutonneuse Fever (R. connori in the Mediterranean)
        2. Queensland Tick Typhus (R. australis in australia)
        3. African Tick BiteFever (R. africae in africa)
        4. Siberian Tick Typhus (R. sibirica in China)
  3. Pathophysiology
    1. Transmission
      1. Tick to human transmission
        1. Transmission may occur as early as 2 hours after Tick Bite
        2. Tick engorgement need not be present for transmission to have occurred
      2. Person to person transmission does not occur
      3. Tick Bite (Ixodidae tick)
        1. Wood tick (Dermacentor andersoni) is vector in Western U.S.
        2. Dog tick (Dermacentor variabilis) is vector in Southern and Eastern U.S.
      4. Other ticks transmitting spotted fever group Bacteria
        1. Rhipicephalus
        2. Amblyomma Maculatum (Gulf Coast Tick)
    2. Rickettsia rickettsii is causative organism
      1. Gram Negative Bacteria
      2. Small pleomorphic organism
      3. Obligate intracellular Parasite
    3. Infects blood vessel walls
      1. Infects endothelial cells and Smooth Muscle Cells,
      2. Spreads through Lymphatic System
      3. Secondary multiorgan Small Vessel Vasculitis ensues (especially involving skin and Adrenal Glands)
      4. Results in increased vascular permeability and decreased osmotic pressure
  4. Presentation: Classic
    1. Classic presentation in <18% of patients
    2. Initial
      1. Recent Tick Bite in endemic areas
      2. Fever and flu-like illness in spring and summer
      3. Headache
    3. Later (day 6)
      1. Erythematous, Macular rash (transitions to Petechiae)
  5. Symptoms (follows 5-7 day incubation)
    1. Fever
    2. Frontal Headache
    3. Myalgias (back and leg Muscles)
    4. Malaise
    5. Nausea or Vomiting
    6. Abdominal Pain (especially in children)
  6. Signs: Rash (occurs in 90-95% of patients)
    1. Onset in first week of illness (follows fever by 2-5 days)
    2. Characteristics
      1. Initial: Pink blanching Macules 1 to 4 mm in diameter
      2. Later: Macules transition to Papules and Petechiae (seen in 40-50% of patients)
      3. Final: Coalesce into large Ecchymoses and ulcerations (eschar may form)
    3. Distribution: Centripetal Rash - peripheral to central spread
      1. Onset: Wrists and ankles
      2. Next: Spreads distally to palms and soles (may be only rash in as many as 40% of patients)
      3. Next: Spreads proximally into upper arms and legs
      4. Later: Trunk, axilla, buttocks, neck
      5. Face is typically spared
  7. Diagnosis
    1. Missed diagnosis initially in up to 75% of cases
      1. Delayed onset of rash until day 6 makes initial diagnosis more difficult
      2. Start empiric management immediately on suspicion
    2. Based on clinical findings
      1. Do not rely on rash or Thrombocytopenia to make diagnosis
    3. Specific testing is for confirmation only
      1. Skin biopsy with immunofluorescent Rickettsia stain
      2. RickettsiaSerology
  8. Differential Diagnosis
    1. See Purpura Causes
    2. See Febrile Eruption
    3. See Tick Borne Illness
    4. Ehrlichiosis
    5. Mycoplasma pneumonia
    6. Syphilis
    7. Lyme Disease
    8. Coxsachievirus
    9. Mononucleosis
    10. Parvovirus B19
    11. Kawasaki Disease
    12. Leptospirosis
    13. Roseola
    14. Rubeola
    15. Meningococcemia
    16. Toxic Shock Syndrome
    17. Scarlet Fever
    18. Immune Thrombocytopenic Purpura
  9. Labs
    1. Complete Blood Count
      1. White Blood Cell Count normal or slightly decreased (Leukopenia)
      2. Thrombocytopenia
    2. Liver Function Test abnormalities
      1. Serum Bilirubin increased (Hyperbilirubinemia)
      2. Liver transaminases increased
        1. Aspartate Aminotransferase (AST) increased
        2. Alanine Aminotransferase (ALT) increased
    3. Renal Function tests (Serum Creatinine and Blood Urea Nitrogen)
      1. Acute Renal Failure is a late finding
    4. Serum Sodium
      1. Hyponatremia
    5. Cerebrospinal Fluid (indicated for associated neurologuc changes)
      1. CSF Pleocytosis with monocytic predominance
  10. Diagnosis
    1. Skin Punch Biopsy with immunofluorescent stain for Rickettsia
      1. Used for confirmation, not for diagnosis
      2. Test Sensitivity: 60%
      3. Test Specificity: Very high
    2. RickettsiaSerology
      1. Positive 7 to 10 days after symptom onset
      2. Used for confirmation, not for diagnosis
      3. IgG increases 4 fold from baseline when re-tested 2-4 weeks later
  11. Management
    1. Start empiric treatment immediately when diagnosis suspected
      1. Do not delay treatment for diagnostic testing
      2. Treatment delayed >5 days after onset increases mortality by 3 fold
      3. Treatment is ideally started before rash onset (typically develops day 6)
    2. Antibiotic Course
      1. Minimum course: 7 days
      2. Continue antibiotics until afebrile for 3 days
    3. Antibiotics
      1. Doxycycline for 7 days
        1. Adult: 100 mg oral or IV twice daily
        2. Child (<45 kg) 2.2 mg/kg (max 100 mg) twice daily
          1. Children of any age and pregnant women should be treated with Doxycycline despite dental risks
          2. Only effective treatment available for a condition with high risk for mortality
      2. Chloramphenicol (only if Doxycycline contraindicated)
        1. Dose: 12.5 mg/kg orally four times daily for 7 days
        2. Higher mortality than with Doxycycline
  12. Complications
    1. Encephalitis (and cerebral edema)
    2. Noncardiac Pulmonary Edema and Pulmonary Hemorrhage
    3. Acute Respiratory Distress Syndrome (ARDS)
    4. Acute Renal Failure
    5. Myocarditis
    6. Cardiac Arrhythmia
    7. Disseminated Intravascular Coagulation
    8. Gastrointestinal Bleeding
    9. Skin Necrosis
  13. Prognosis
    1. Untreated: 20-25% Mortality within 7 to 15 days (median 7 days)
    2. Treated: 4-5% Mortality
    3. Children have a higher mortality rate than adults
    4. G6PD is associated with complications and poor outcome
  14. Prevention
    1. See Prevention of Vector-borne Infection
  15. Resources
    1. CDC Rocky Mountain Spotted Fever
  16. References
    1. (2016) Sanford Guide to Antibiotics, IOS App accessed 4/14/2016
    2. Chapman (2006) MMWR Recomm Rep 55(RR-4):1-27 [PubMed]
    3. Cunha (2008) Lancet Infect Dis 8(3): 143-4 [PubMed]
    4. Huntington (2016) Am Fam Physician 94(7): 551-7 [PubMed]
    5. Pace (2020) Am Fam Physician 101(9): 530-40 [PubMed]
    6. Thorner (1998) Clin Infect Dis 27:1353-60 [PubMed]

Rocky Mountain Spotted Fever (C0035793)

Definition (MSH) An acute febrile illness caused by RICKETTSIA RICKETTSII. It is transmitted to humans by bites of infected ticks and occurs only in North and South America. Characteristics include a sudden onset with headache and chills and fever lasting about two to three weeks. A cutaneous rash commonly appears on the extremities and trunk about the fourth day of illness.
Definition (CSP) acute, infectious, sometimes fatal disease caused by Rickettsia rickettsii usually transmitted by ixodid ticks; occurs only in North and South America; manifestations include chills, fever, rash, headache, myalgia, and prostration.
Concepts Disease or Syndrome (T047)
MSH D012373
ICD10 A77.0
SnomedCT 186772009, 49729004, 154375001, 413710009, 4460007, 266205000, 186771002
LNC LA10501-7
English Sao Paulo Typhus, Typhus, Sao Paulo, ROCKY MOUNTAIN SPOTTED FEVER, Rocky mountain spotted fever, Fiebre macuculosa, Fiebre manchada, Fiebre petequial, RMSF - Rocky Mountain spot fev, Sao Paulo tick typhus, South American tick typhus, Spotted fever due to Rickettsia rickettsii, Sao Paulo typhus, Rocky mountain spotted fever (diagnosis), Sao Paulo fever (diagnosis), Rickettsia rickettsii infection, Rocky Mountain Spotted Fever [Disease/Finding], fever mountain rocky spotted, rocky spotted mountain fever, rocky mountain spotted fever, rocky mountain tick fever, spotted fever due to rickettsia rickettsii (diagnosis), spotted fever due to Rickettsia rickettsii, Sao Paulo fever (disorder), Rocky mountain spotted fever (disorder), RMSF - Rocky Mountain spotted fever, Rocky Mountain spotted fever (disorder), Rocky Mountain Spotted Fever, Rocky Mountain spotted fever, Rocky Mountain tick fever, Rickettsia; rickettsii, spotted fever, Rocky Mountain fever, Rocky Mountain; spotted fever, Sao Paulo fever or typhus, Sao Paulo; fever, Sao Paulo; spotted fever, fever; Sao Paulo, fever; mountain, Rocky Mountain spotted fever, mountain; fever, Rocky Mountain spotted fever, rickettsii; Rickettsia rickettsii, spotted fever, rickettsiosis; Rickettsia rickettsii, spotted fever; Rickettsia rickettsii, spotted fever; Rocky Mountain, spotted fever; Sao Paulo, Rocky mountain tick fever, Spotted fever due to Rickttsia rickettsii, Rocky mountain spotted fever (disorder) [Ambiguous], Sao Paulo fever
Italian Febbre a macchie delle montagne rocciose, Infezione da Rickettsia rickettsii, Febbre di Sao Paulo, Febbre maculosa delle Montagne Rocciose
Dutch Rickettsia rickettsii-infectie, Rickettsia; rickettsii, spotted fever, Rocky Mountain; spotted fever, Sao Paulo; koorts, Sao Paulo; spotted fever, fever; mountain, Rocky Mountain spotted fever, koorts; Sao Paulo, mountain; fever, Rocky Mountain spotted fever, rickettsii; Rickettsia rickettsii, spotted fever, rickettsiose; Rickettsia rickettsii, spotted fever; Rickettsia rickettsii, spotted fever; Rocky Mountain, spotted fever; Sao Paulo, Rocky Mountain spotted fever, Fever, Rocky Mountain spotted, Sao Paulo-tyfus, Spotted fever door Rickettsia rickettsii, Spotted fever, Rocky Mountain, Tyfus, Sao Paulo
French Infection à Rickettsia rickettsii, Fièvre pourprée nord-américaine, Fièvre tachetée des Montagnes Rocheuses, Fièvre pourprée des montagnes rocheuses, Fièvre pourprée des Montagnes Rocheuses, Fièvre pourprée à Rickettsia rickettsii, Typhus de Sao Paulo
German Rickettsia rickettsii-Infektion, Zeckenbissfieber durch Rickettsia rickettsii, Rocky-Mountain-Fleckfieber, Sao-Paulo-Typhus, Typhus, Sao-Paulo-
Portuguese Infecção por Rickettsia rickettsii, Febre Maculosa Brasileira, Febre Maculosa, Febre Maculosa de São Paulo, Febre das Montanhas Rochosas, Febre Maculosa das Montanhas Rochosas, Tifo de São Paulo
Spanish Infección por Rickettsia rickettsii, fiebre manchada ocasionada por Rickettsia rickettsii, fiebre manchada ocasionada por Rickettsia rickettsii (trastorno), fiebre de San Pablo (trastorno), fiebre negra, fiebre manchada de las Rocallosas (trastorno), fiebre azul, fibre mnchada de las Rocallosas (trastorno), fibre mnchada de las Rocallosas, fiebre de las Montañas Rocosas, fiebre manchada de las Montañas Rocallosas, fiebre manchada de las Montañas Rocosas (trastorno), fiebre manchada de las Montañas Rocosas, fiebre manchada de las Rocallosas (concepto no activo), fiebre manchada de las Rocallosas, fiebre manchada por Rickettsia rickettsii, rickettsiosis exantemática americana, Fiebre exantemática de las Montañas Rocosas, fiebre de San Pablo, fiebre exantemática de las Montañas Rocosas, Fiebre Maculosa de las Montañas Rocosas, Fiebre de São Paulo
Japanese ロッキー山紅斑熱リケッチア感染, ロッキーサンコウハンネツ, ロッキーサンコウハンネツリケッチアカンセン, ロッキー山紅斑熱, Sao Pauloチフス, サンパウロチフス, チフス-Sao Paulo, チフス-サンパウロ
Swedish Klippiga bergen-fläckfeber
Czech horečka Skalistých hor, Horečka Skalistých hor, Infekce Rickettsia rickettsii
Finnish Kalliovuorten pilkkukuume
Korean 리켓치아 리켓치에 의한 홍반열
Polish Gorączka Gór Skalistych, RMSF, Dur plamisty Sao Paolo, Gorączka plamista Gór Skalistych
Hungarian Rickettsia rickettsii fertőzés, Sziklás hegységi foltos láz
Norwegian Flekkfeber som skyldes Rickettsia rickettsii, Rocky Mountains-flekkfeber, São Paulo-feber
Derived from the NIH UMLS (Unified Medical Language System)

Rickettsia rickettsii antigen (C0369943)

Concepts Immunologic Factor (T129)
SnomedCT 120979009
LNC LP39595-1, MTHU022947
English Rickettsia rickettsii Antigen, Rickettsia rickettsii Ag, Rickettsia rickettsii antigen (substance), Rickettsia rickettsii antigen
Spanish antígeno de Rickettsia rickettsii (sustancia), antígeno de Rickettsia rickettsii
Derived from the NIH UMLS (Unified Medical Language System)

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