Sections View Full Chapter Figures Tables Videos Annotate Full Chapter Figures Tables Videos Supplementary Content + Download Section PDF Listen ++ For further information, see CMDT Part 32-12: Spotted Fevers + Key Features Download Section PDF Listen +++ ++ 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 + Clinical Findings Download Section PDF Listen +++ ++ 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 + Diagnosis Download Section PDF Listen +++ ++ 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 + Treatment Download Section PDF Listen +++ ++ 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