Antibodies to Borrelia turicatae in experimentally-infected dogs cross-react with B. burgdorferi serologic assays

Tick-borne relapsing fever (TBRF) is caused by several Borrelia spp (including Borrelia turicatae ). which are primarily transmitted by Ornithodoros ticks. Relapsing fever group species are found worldwide except for Antarctica. Approximately 500 human cases were reported between 1990-2011 in the United States (likely an underestimate), while cases in domestic and wild dogs were reported from Florida, Texas, and Washington. TBRF spirochetes are related to Borrelia burgdorferi , the agent of Lyme borreliosis. Dogs are routinely screened for B. burgdorferi, but it is unknown if infection with TBRF agents produce antibodies cross-reactive with B. burgdorferi assays. These data are critical for accurate surveillance of TBRF and Lyme borreliosis in dogs. In this study, B. burgdorferi- negative dogs were inoculated with B. turicatae and seroconversion was confirmed by the rBipA Western blot. Seropositive samples were tested with commercial and veterinary diagnostic laboratory B. burgdorferi- based tests. Borrelia turicatae-seroreactive samples cross-reacted with a whole cell IFA and two multi-antigen tests; but not with single antigen tests using C6. Cross-reactivity with TBRF can confound epidemiology and surveillance efforts, and confuse recommendations made by veterinarians for prevention and control. These findings demonstrate the need to critically evaluate results of B. burgdorferi diagnostic tests in the context of the assay type, the animal9s geographical location, and history of travel as well as highlighting the need for commercially-available specific diagnostic tests for TBRF spirochetes.