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 34-08: Relapsing Fever + Key Features Download Section PDF Listen +++ ++ Infectious organisms are spirochetes of the genus Borrelia In the United States, infected ticks are found throughout the west, especially in mountainous areas Human clinical cases are uncommon, however, large epidemics may occur Both tick-borne and louse-borne disease occur Tick-borne disease Main reservoir is rodents, which serve as the source of infection for ticks Not transmitted from person to person Louse-borne disease: lice transmit Borrelia from an infected person + Clinical Findings Download Section PDF Listen +++ ++ Abrupt onset of fever, chills, tachycardia, nausea and vomiting, arthralgia, and severe headache Hepatomegaly and splenomegaly, rashes Delirium, neurologic and psychological abnormalities The attack terminates, usually abruptly, after 3–10 days After an interval of 1–2 weeks, relapse occurs, and 3–10 relapses may occur before recovery Three to 10 relapses may occur before recovery in tick-borne disease, whereas louse-borne disease is associated with only 1 or 2 relapses + Diagnosis Download Section PDF Listen +++ ++ During fever, large spirochetes are seen in thick and thin blood smears stained with Wright or Giemsa stain Organisms can be cultured in special media but rapidly lose pathogenicity Anti-Borrelia antibodies develop during the illness The Weil-Felix test for rickettsioses, nontreponemal serologic tests for syphilis, and indirect fluorescent antibody and Western blot tests for Borrelia burgdorferi may be falsely positive Polymerase chain reaction (PCR) assays can be performed on blood, CSF and tissue but are not always available in endemic regions Cerebrospinal fluid abnormalities occur in patients with meningeal involvement Mild anemia and thrombocytopenia are common but white blood cell count tends to be normal Differential diagnosis Malaria Leptospirosis Meningococcemia Yellow fever Typhus Rat-bite fever + Treatment Download Section PDF Listen +++ ++ Tick-borne relapsing fever Treatment begins with penicillin G, 3 million units intravenously every 4 hours, or ceftriaxone, 1 g intravenously daily With clinical improvement, a 10-day course can be completed with 0.5 g of tetracycline or erythromycin given orally four times daily All pregnant women with tick-borne disease should be treated for 14 days, ideally with intravenous penicillin or ceftriaxone Louse-borne relapsing fever: tetracycline or erythromycin, 0.5 g orally once, or procaine penicillin G, 600,000–800,000 units intramuscularly once If CNS invasion is suspected, intravenous penicillin G or ceftriaxone should be continued for 10–14 days Jarisch-Herxheimer reactions Occur commonly and may be life-threatening Administration of anti-TNF antibodies prior to antibiotic therapy can be effective in preventing these reactions With treatment, the initial attack is shortened and relapses are largely prevented Overall mortality rate is ~5% Fatalities most common in old, debilitated, or very young patients Prevention of relapsing fever is by prevention of tick bites and delousing procedures