Tick-borne relapsing fever

**Definition:** A disease caused by an infection with the bacteria Borrelia. This disease is characterised by repeated episodes of fever, with the febrile episode lasting for approximately 3 days, followed by the afebrile state of approximately 7 days. Transmission is through the bite of an infected soft tick (from the genus Ornithodoros). Confirmation is by identification of spirochete bacteria from a blood smear, bone marrow, or cerebrospinal fluid.

**Long definition:** Tick-borne relapsing fever is due to the sporadic transmission of one of a number of Borrelia species by soft ticks of the genus Ornithodorus to a human host. Tick-borne relapsing fever is found primarily in Africa and Asia. It produces a clinical picture similar to but less severe than that seen in louse-borne relapsing fever. It is characterized by episodes of high fever with severe systemic upset.

**Inclusions:** - Relapsing fever due to any Borrelia species other than Borrelia recurrentis