Antibodies to Borrelia turicatae in Experimentally Infected Dogs Cross-React with Borrelia 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 and 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 produces 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 (recombinant Borrelia immunogenic protein A) 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 indirect fluorescent antibody (IFA) test and two multiantigen 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 from B. burgdorferi diagnostic tests in the context of the assay type and the animal's geographical location and history of travel, as well as highlighting the need for commercially available specific diagnostic tests for TBRF spirochetes.

Tick-Borne Relapsing Fever Spirochetes in the Americas.

Relapsing fever spirochetes are tick- and louse-borne pathogens that primarily afflict those in impoverished countries. Historically the pathogens have had a significant impact on public health, yet currently they are often overlooked because of the nonspecific display of disease. In this review, we discuss aspects of relapsing fever (RF) spirochete pathogenesis including the: (1) clinical manifestation of disease; (2) ability to diagnose pathogen exposure; (3) the pathogen's life cycle in the tick and mammal; and (4) ecological factors contributing to the maintenance of RF spirochetes in nature.