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Tick-borne Relapsing Fever spirochetes

Peripheral blood smear. The TBRF bacteria are long and spiral-shaped. The circular objects are red blood cells. The irregular purple object in the top right corner is a white blood cell.

Relapsing Fever Bacteria

Relapsing fever is caused by certain species of Borrelia,
a gram negative bacteria 0.2 to 0.5 microns in width and 5 to 20 microns in length. They are visible with light microscopy and have the cork-screw shape typical of all spirochetes. Relapsing fever spirochetes have a unique process of DNA rearrangement that allows them to periodically change the molecules on their outer surface. This process, called antigenic variation, allows the spirochete to evade the host immune system and cause relapsing episodes of fever and other symptoms. Three species cause TBRF in the United States: Borrelia hermsii, B. parkerii, and B. turicatae. The most common cause is cause is B. hermsii.

Clinical Disease

Relapsing fever is characterized by episodes of fever lasting several days, followed by an interval without fever, followed by another episode of fever. This process can recur from 1 to 4 times. Along with fever, patients may experience generalized body aches, muscle pain, joint pain, headache, nausea, vomiting, anorexia, dry cough, light sensitivity, rash, neck pain, eye pain, confusion, and dizziness.  If you suspect that you have relapsing fever, see your health care provider.

Timing of Relapses

Relapsing fever is characterized by an incubation period of roughly one week, followed by an episode of fever lasting several days, followed by an interval without fever. This process can recur from 1 to 4 times if untreated.

General timeline for TBRF relapse intervals.

 
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