Prevalence, distribution, and phylogenetics of the tick-borne relapsing fever spirochete Borrelia turicatae in the soft tick Ornithodoros turicata americanus in Florida

In the southwestern United States, the occurrence and potential for disease spread of Tick-Borne Relapsing Fever (TBRF) has been studied. In Florida, Borrelia pathogens that cause TBRF have only been found in two domestic dogs (Canis lupus familiaris), yet the soft tick vector, Ornithodoros turicata americanus, is commonly found throughout the state. The goal of our study was to provide the first large-scale investigation of this disease system in the southeastern US. Our objectives were to: 1) describe the occurrence and prevalence of Borrelia spp. in ticks found throughout their distribution; and 2) phylogenetically describe the pathogen species compared to other isolates of B. turicatae. We pooled ticks by sample location and extracted DNA from over 3,000 ticks systematically collected throughout Florida. Conventional PCR was used with a genus-wide IGS primer to detect any Borrelia spp. present in the ticks. We discovered a low but detectable prevalence (7/745; 0.94%) of the pathogen within localized foci, which could present an epidemiological risk to humans and companion animals in those areas. We Sanger sequenced the 7 pools that were positive for Borrelia spp. and created a phylogenetic tree with our samples and 27 previously described isolates. Our tree showed clustering of our samples into two distinct clades, one that fit with Texas isolates and one that was entirely distinct. We hypothesized that a combination of biogeographic and host influences may be the driving force behind the history of Borrelia turicatae in Florida. Future research is needed to improve our understanding of the drivers of pathogen occurrence and the phylogeography of this species. By understanding the occurrence and phylogenetics of Borrelia turicatae in the state, we can better comprehend and mitigate the risk of this neglected vector-borne disease for humans and companion animals in Florida.