Tick-borne relapsing fever (TBRF) is an underrecognized infectious disease that primarily affects people, with increasing recognition in dogs. TBRF is caused by several different species of spirochete Borrelia bacteria, mostly Borrelia turicatae and Borrelia hermsii in the United States. Infections with both of these species have been reported in dogs.1'4 Borrelia turicatae and B. hermsii are transmitted by Ornithodoros spp. of soft ticks, which have different biologic behaviors than hard ticks. Dogswith TBRF can present with nonspecific signs of illness or with signs of neurologic, joint, and/or ocular disease. This infection is likely underreported in veterinary medicine, or mistakenly diagnosed as Lyme disease due to serologic testing crossreactions.4-6 The hallmark feature of TBRF is the presence of numerous spirochete bacteria on standard peripheral blood smears. The recent development of a commercial PCR assay by our research team will improve recognition and characterization of this infection.
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