INTRODUCTION — Rocky Mountain spotted fever (RMSF) is a potentially lethal, but usually curable, tick-borne disease. It occurs throughout the United States, Canada, Mexico, Central America, and in parts of South America. The etiologic agent, Rickettsia rickettsii, is a gram-negative, obligate intracellular bacterium that causes a wide spectrum of clinical disease from mild to fulminant infection.
The basic biology of R. rickettsii, and the epidemiology, clinical manifestations, and diagnosis of RMSF are discussed separately.
Approach to treatment depends upon the certainty of disease and the severity of symptoms. Empiric therapy with doxycycline should be started if the diagnosis of Rocky Mountain spotted fever (RMSF) is suspected, even if the symptoms are mild.
Assessing likelihood of RMSF — A diagnosis of RMSF is likely in patients who present with fever, headache, and constitutional symptoms in the spring and summer months if:
●They are from an endemic area
●Have a known or possible tick bite
On occasion, a patient from a region endemic for RMSF may present with mild nonspecific symptoms without a rash, and without risk factors for exposure to a tick. Although the diagnosis of RMSF is unlikely in such patients, in certain settings, treatment may still be indicated.
Patients likely to have RMSF — Antimicrobial therapy should be initiated as soon as possible in all patients who are likely to have RMSF.
It is particularly important that empiric therapy not be delayed if RMSF is suspected in patients who are severely ill and/or those who present with possible complications associated with RMSF (eg, seizures, hypotension, noncardiogenic pulmonary edema, jaundice).
Most patients will require empiric therapy for RMSF based upon clinical judgment and the epidemiologic setting since RMSF can rarely be confirmed or disproved in its early phase. Clinicians should not wait for the skin rash to develop before initiating treatment.
Patients with mild disease can generally be treate