Rocky Mountain Spotted Fever

Caused by Rickettsia rickettsii, a parasite of ticks, transmitted by tick bites

Most cases occur in only five states: North Carolina, South Carolina, Tennessee, Oklahoma, and Arkansas

Most cases occur in late spring and summer

Typical incubation period is 2–14 days (median, 7 days)

Mortality rate is over 70% in untreated patients

Initial symptoms include fevers, chills, headache, nausea and vomiting

Cough and pneumonitis often occur early in the disease

In more severe cases, delirium, lethargy, seizures, stupor, and coma may also appear

Rash (not always found) begins as a faint macule that progresses to large maculopapules and often petechiae

Rash begins on the wrists and ankles, characteristically involves palms and soles, and spreads to arms, legs, and trunk

Splenomegaly, hepatomegaly, jaundice, myocarditis (which may mimic an acute coronary syndrome), adrenal hemorrhage, polyarticular arthritis, or uremia are occasionally present

About 3–5% of recognized cases in the United States are fatal

Thrombocytopenia

Hyponatremia

Hepatitis

CSF low glucose

Immunohistologic staining for R rickettsii in skin biopsy specimens and serologic testing are the keys to a definitive diagnosis

Doxycycline (100 mg orally twice daily for 4–10 days) or chloramphenicol (50–100 mg/kg/day in four divided doses, orally or intravenously for 4–10 days) are usually highly effective

Prevention: protective clothing and avoiding tick bites