Infection with Borrelia recurrentis: Pathogenesis of Fever and Petechiae

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Abstract
Patients infected with the spirochete Borrelia recurrentis were studied to determine the cause of fever and mechanism of petechia formation. The limulus test for endotoxin was applied to plasma. Spirochetes were concentrated from the blood by differential centrifugation and tested for endotoxin activity. Endotoxemia was detected in only seven of 28 patients tested and was associated with other bacterial infections and marked liver dysfunction. Concentrated spirochetes prepared from the blood of three patients produced fever in rabbits, and this material remained pyrogenic after heating to 100 C for 15 min. Endotoxin-tolerant rabbits did not develop febrile responses to spirochetes, but the spirochetes neither produced positive limulus tests nor prepared rabbits for local Shwartzman reactions. After sonication and centrifugation of spirochete suspensions, pyrogenicity was found only in the sediment. Petechiae, which were observed in 37 (41%) of 90 patients, were biopsied, and their presence was correlated with clinical and laboratory data. Skin biopsies revealed red cells and spirochetes within the dermis without vasculitis or thrombosis. The mean platelet count of 37 patients with petechiae, 34 × 109/liter, was significantly lower than that of 48 × 109/liter in 53 patients without petechiae (P < 0.05). These findings suggested that fever in B. recurrentis infection is caused by a heat-stable, nonendotoxic, particulate pyrogen of the spirochete and that petechiae are the result of thrombocytopenia.