Approach

Antibiotic therapy should be started in symptomatic patients as soon as the diagnosis is reasonably considered, without waiting for the results of tests to confirm the diagnosis. Outcomes are best when anti-rickettsial therapy is initiated within the first 5 days of illness.[1]

First-line antibiotic therapy

Doxycycline is the preferred agent for the treatment of Rocky Mountain spotted fever (RMSF) in patients of all ages due to its efficacy, twice-daily dosing, and favourable safety profile.[1][18]​​[22]

Although repeated courses of tetracycline were associated with staining of permanent teeth in young children, no evidence suggests that doxycycline causes any such tooth staining and it is recommended in children aged <8 years.[22]​[23]​​[24]​​[25]​​

Alternative antibiotic therapy

Chloramphenicol is a possible alternative agent for treatment of RMSF.[19]​ However, for several reasons doxycycline is preferred over chloramphenicol for both adults and children with suspected RMSF:[1]

  • Patients treated with chloramphenicol for RMSF have an increased case fatality rate compared to those treated with doxycycline.

  • Doxycycline is effective for treatment of human monocytic ehrlichiosis and granulocytic anaplasmosis, and other spotted fever group rickettsioses that clinically mimic RMSF, whereas chloramphenicol may not be.

  • Chloramphenicol is associated with numerous adverse effects (e.g., aplastic anaemia, Grey baby syndrome), and the oral formulation is no longer available in the US, although it is still widely used in Europe and several countries worldwide.

The Centers for Disease Control and Prevention (CDC) emphasises that the use of antibiotics other than doxycycline increases the risk of patient death. In cases of severe doxycycline allergy, rapid desensitisation procedures may be considered in an inpatient setting. The care of patients with a doxycycline allergy should be undertaken in consultation with an infectious diseases consultant.[18][19]

Pregnant women

The care of pregnant women with suspected RMSF should be undertaken in consultation with an infectious-disease consultant.[18] Pregnant women should be counselled on the potential risks and benefits when making a treatment decision.​

  • Tetracyclines are generally contra-indicated in pregnant women, due to their potential toxicity to both fetus and mother.[1]

  • However, the CDC recommends doxycycline as the first-line option in pregnant women.[19]​ The safety of doxycycline has not been assessed in controlled studies in pregnant women; however, one review concluded that the risk of teratogenicity is unlikely, although data were insufficient to conclude that no risk exists.[26] Doxycycline has been used successfully to treat rickettsial disease in pregnant women without adverse effects; however, follow-up to assess toxicity was limited.[1]

Other bacterial infections

For those whose presentation may be consistent with a serious different bacterial infection, therapy needs to begin presumptively, and empirical antibiotics are indicated until blood cultures or clinical course rule out the alternative diagnosis. An antibiotic active against Neisseria meningitidis, such as a parenteral third-generation cephalosporin, is also appropriate for other bacterial infections that can occasionally mimic RMSF (e.g., pneumococcal bacteraemia in asplenic hosts). If sepsis or toxic shock syndrome caused by Staphylococcus aureus cannot be excluded, empirical therapy is appropriate.

Patients with RMSF who receive therapy within the first week of illness will generally show signs of improvement, including defervescence, within 72 hours of initiating doxycycline therapy; lack of improvement suggests the need to search for an alternative diagnosis.[1][12]

Critically ill patients

Patients with RMSF who are ill enough to be hospitalised may require aggressive supportive-care interventions. Fluid balance and serum electrolytes should be monitored closely. Some patients may need transfusions of packed red blood cells or platelets. Critically ill patients might require adjunctive therapies for seizures, intracranial hypertension, shock, acute respiratory distress syndrome, renal failure, or other complications.[1][11]​​

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