Rocky Mountain Spotted Fever




Rocky Mountain spotted fever is caused by bacteria called Rickettsia rickettsii that are transmitted by the bite of a tick.  Initial signs and symptoms of Rocky Mountain spotted fever often are nonspecific and can mimic those of other illnesses:High fever, Chills, Severe headache, Muscle aches, Nausea and vomiting, Restlessness and insomnia.  Thirty percent of untreated patients die. It is treatable with antibiotics, often doxycycline.



According to the CDC


There are several aspects of RMSF that make it challenging for healthcare providers to diagnose and treat. The symptoms of RMSF vary from patient to patient and can easily resemble other, more common diseases. Treatment for this disease is most effective at preventing death if started in the first five days of symptoms. Diagnostic tests for this disease, especially tests based on the detection of antibodies, will frequently appear negative in the first 7-10 days of illness. Due to the complexities of this disease and the limitations of currently available diagnostic tests, there is no test available at this time that can provide a conclusive result in time to make important decisions about treatment.


For this reason, healthcare providers must use their judgment to treat patients based on clinical suspicion alone. Healthcare providers may find important information in the patient’s history and physical examination that may aid clinical suspicion. Information such as recent tick bites, exposure to high grass and tick-infested areas, contact with dogs, similar illnesses in family members or pets, or history of recent travel to areas of high incidence can be helpful in making the diagnosis. Also, information about the presence of symptoms such as fever and rash may be helpful. The healthcare provider may also look at routine blood tests, such as a complete blood cell count or a chemistry panel. Clues such as a low platelet count (thrombocytopenia), low sodium levels (hyponatremia), or elevated liver enzyme levels are often helpful predictors of RMSF but may not be present in all patients. After a suspect diagnosis is made on clinical suspicion and treatment has begun, specialized laboratory testing should be used to confirm the diagnosis of RMSF.


The diagnosis of RMSF must be made based on clinical signs and symptoms, and can later be confirmed using specialized confirmatory laboratory tests. Treatment should never be delayed pending the receipt of laboratory test results, or be withheld on the basis of an initial negative finding for R. rickettsii.


Recommended Dosage (CDC)
Doxycycline is the first line treatment for adults and children of all ages:

  • Adults: 100 mg every 12 hours

  • Children under 45 kg (100 lbs): 2.2 mg/kg body weight given twice a day

Patients should be treated for at least 3 days after the fever subsides and until there is evidence of clinical improvement. Standard duration of treatment is 7-14 days.