Rocky Mountain Spotted Fever

GENERAL PRINCIPLES

RMSF is an acute febrile illness caused by Rickettsia rickettsii and transmitted by a variety of ticks, most commonly Dermacentor variabilis (dog tick). The regions with highest endemicity include the South Atlantic (North and South Carolina and Virginia) and South Central US (Oklahoma, Arkansas, and Tennessee).

Clinical Presentation

The classic triad of fever, headache, and rash is often not present in the early phases of the disease. The typical petechial rash with centripetal distribution (starting on the distal extremities and extending to the trunk) will be present in 90% between the third and fifth days of illness. Presumptive diagnosis can be based on the clinical syndrome and warrants immediate treatment.

DIAGNOSIS

Acute and convalescent serologies support the diagnosis; however, early treatment may abolish the appearance of antibodies in the convalescent phase. PCR or immunostaining of tissue samples, such as skin biopsies, are highly specific.

TREATMENT

Antibiotic treatment of choice is doxycycline 100 mg IV/PO q12h for 7 days or continued for 3 days after the patient defervesce. Chloramphenicol is an alternative.

OutcomeZPrognosis

If treatment is delayed, RMSF is the most likely tick-borne illness to result in death or serious sequelae.⁴³