A 51-year-old man with tick-borne relapsing fever

A 51-year-old man presented to hospital with a 2-week history of fever, chills, headache, dyspnea, dry cough, gastrointestinal symptoms, transient pruritic arm rash, and blurred vision after he was bitten by insects while gardening at a cabin in rural British Columbia.No other travel history was noted.On admission, he was febrile (39.1C), anemic (hemoglobin 110 [reference range 135 to 180] g/L), thrombocytopenic (platelets 92 [reference range 150 to 400] 10 9 /L), and hyperglycemic (blood glucose 34 [reference range 3.6 to 7.8] mmol/L), with an elevated C-reactive protein level (139 [reference range < 7.5] mg/L).A blood smear revealed spirochetes (Figure 1); serologic testing for Borrelia burgdorferi was reactive, suggesting Lyme disease.As visible spirochetes are uncommon in Lyme disease, however, we broadened the differential diagnosis to include tickborne relapsing fever (TBRF), babesiosis, anaplasmosis, and ehrlichiosis.Polymerase chain reaction (PCR) testing of an acute blood sample was positive for Borrelia hermsii, confirming TBRF.We treated the patient with intravenous (IV) ceftriaxone (2 g daily for 5 d), followed by oral doxycycline (100 mg twice daily for 5 d).Symptoms resolved within 1 week, hematologic indices normalized by 2 weeks, and a repeat PCR was nega tive, indicating infection resolution.Tick-borne relapsing fever is caused by B. hermsii and Borrelia turicatae. 1It causes intermittent febrile episodes, with headache, myalgia, chills, and malaise.Spirochetemia during febrile episodes, cytopenia, and hepatosplenomegaly may occur.Diagnosis should consider clinical presentation, geographic tick exposures, blood smear examination, and molecular testing. 2 Although B. burgdorferi serology was reactive in our patient, it likely represented a false-positive cross-reaction. 2Detection of peripheral blood spirochetes is more typical of B. hermsii, B. turicatae, and Borrelia mayonii infection. 1,2In our patient, hematologic findings were consistent with Borrelia infection, and clinical features and PCR confirmed TBRF.Treatment of TBRF involves doxycycline (100 mg orally or IV twice daily for 7 to 10 d).For patients with severe disease, neurologic involvement, or oral therapy intolerance, alternatives are IV ceftriaxone (2 g IV once daily) or penicillin G (18 to 24 million units/d, divided every 4 h) for 10 to 14 days.Treatment may result in a Jarisch-Herxheimer reaction, a cytokine-mediated inflammatory response with fever, chills, rigors, diaphoresis, tachycardia, and hypotension, 1 which can be managed supportively while antimicrobial therapy is continued.