A Case of Travel-Associated Tick-Borne Relapsing Fever in Wisconsin.

Introduction: Tick-borne relapsing fever is a zoonotic infection caused by members of the Borrelia genus of spirochetes found predominantly in the southwestern United States.

Case presentation: A 65-year-old woman presented to a Wisconsin emergency department with a 2-day history of fevers and altered mental status after returning from a 5-week stay in Colorado. Initial labs were notable for elevated transaminases, thrombocytopenia, mild hyponatremia, mild hypokalemia, and elevated procalcitonin.

Discussion: Rapid identification of patients with tick-borne relapsing fever is essential to minimize morbidity and mortality. Peripheral blood smear - especially during a febrile episode - can serve as a quick and accurate way to diagnose the illness with direct visualization of spirochetes.

Conclusions: Early analysis of a peripheral blood smear can lead to a swift diagnosis of tick-borne relapsing fever, particularly in nonendemic states such as Wisconsin.