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    Card BL-003
Spirochete seen on the blood smear of a febrile patient
Back of Card BL-003
Differential Diagnosis
  • relapsing fever1


A variety of Borrelia species may cause relapsing fever. However, unlike the other spirochetes that cause human disease (the treponemes and leptospires), they are readily stained by the Giemsa or Wright procedure.2

Tick-borne relapsing fever is the only form of the disease in the United States, occurring sporadically during the summer in mountainous Western areas. After a 7-day incubation, illness begins abruptly with high fever, shaking chills, and severe headache, followed by prostration, myalgias, abdominal pain, vomiting, and cough.2

High fever (39.4 to 40.6°C) persists for 3 to 6 days, until the characteristic crisis of defervescence occurs (a sudden fall in temperature accompanied by drenching sweats). Spirochetes are rapidly cleared from the blood and the patient remains afebrile until 6 to 10 days later when mutated organisms appear in the blood in what may be the first of several relapses.2

Of patients with "Borreliosis," 25% to 50% will have visible spirochetes; a positive finding is highly specific.3 Repeated examinations may be necessary to demonstrate the organism, which is not seen in the blood during the afebrile intervals.2


1) Infectious Diseases. (Pocket Picture Guides to Clinical Medicine) WE Farrar & HP Lambert. Baltimore: Williams & Wilkins (l984). p 52. Illustrated. The American and African Trypanosomes have a spiral shape and may also appear on smears (p 70).

(2) "Leptospirosis, relapsing fever, rat-bite fever, and Lyme disease." In: Scientific American Medicine. E Rubenstein & DD Federman (eds). New York: Scientific American (2/88). 7:VII:3-5. Illust.

(3) Medical Microbiology and Infectious Diseases. A Braude. Philadelphia: Saunders (1981). pp 490-5.

(-) Laboratory Diagnosis of Infectious Diseases. A Balows et al. New York: Springer (1988). pp 105-110.

   Zebra Cards: An Aid to Obscure Diagnoses. JG Sotos. Philadephia: American College of Physicians, 1989. ISBN 0-943126-13-4. Copyright © 1989 American College of Physicians. All Rights Reserved. Phone: 1-800-523-1546.
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©1986-2000 John Sotos, MD. All rights reserved.

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