From the Guidelines
Rocky Mountain spotted fever (RMSF) should be treated immediately with doxycycline upon suspicion, regardless of age, to significantly improve outcomes and reduce mortality risk. The disease is a potentially fatal tick-borne illness caused by the bacterium Rickettsia rickettsii, and early treatment is crucial as delayed therapy beyond the fifth day of illness significantly increases mortality risk 1. Doxycycline is the first-line treatment, typically prescribed at 100mg twice daily for adults and 2.2 mg/kg twice daily for children under 45kg, for a minimum of 5-7 days and at least 3 days after fever subsides.
Some key considerations for the management of RMSF include:
- The classic triad of fever, rash, and reported tick bite is rarely present when patients with RMSF first seek care 1.
- Rash is present in most patients during the course of RMSF, although it can appear late or be atypical, localized, faint, evanescent, and difficult to recognize in persons with darker pigmented skin 1.
- Thrombocytopenia, increased immature neutrophils, elevations in hepatic transaminase levels, and hyponatremia might be present in patients with RMSF; however, laboratory findings are often within or slightly deviated from the reference ranges early in the course of illness 1.
- Prevention involves wearing protective clothing, using tick repellents containing DEET, checking for ticks after outdoor activities, and removing attached ticks promptly with fine-tipped tweezers.
The outcome for confirmed cases of RMSF is significantly improved when treatment with doxycycline is started early, with a notable increase in mortality risk when treatment is delayed beyond the fifth day of illness 1. Doxycycline is the preferred treatment for RMSF, even in pregnant women, although chloramphenicol may be considered as an alternative in certain cases. Prompt recognition and antibiotic treatment are crucial to prevent severe disease and fatal outcomes.
From the Research
Overview of Rocky Mountain Spotted Fever
- Rocky Mountain spotted fever (RMSF) is a potentially deadly disease caused by Rickettsia rickettsii, transmitted to humans by infected ticks 2, 3, 4.
- The disease can present subtly with signs and symptoms overlapping with other clinical conditions, making diagnosis challenging 2, 3, 4.
Clinical Features
- Symptoms of RMSF include fever, headache, photophobia, malaise, myalgias, and a petechial rash that begins on the wrists and ankles and spreads to the trunk 2, 3.
- Rash may not occur in ≤15% of patients, and the classic triad of fever, headache, and rash is not definitive 2.
- Laboratory evaluation may demonstrate hyponatremia, anemia, thrombocytopenia, abnormal liver enzymes, and elevated coagulation tests 2.
Diagnosis and Treatment
- Diagnosis of RMSF is based on the patient's history and physical examination, and often presents a dilemma for clinicians due to the non-specific presentation of the disease in its early course 4, 5.
- Early empirical treatment with doxycycline is essential to prevent severe complications or a fatal outcome, and treatment should be initiated even in unconfirmed cases 2, 6, 5.
- Delayed recognition and treatment can lead to increased morbidity and mortality, with mortality rates of 4% when treatment is initiated within the first five days of illness, and 35% when treatment is delayed beyond Day five 6.