A longitudinal study in central Texas suggests small rodent species are reservoirs for the zoonotic relapsing fever spirochete, Borrelia miyamotoi

Tick-borne diseases are emerging worldwide, causing significant illness and death in human and animal populations.  The southern United States is an area of particular concern for tick-borne disease emergence due to high tick species diversity and longer periods of seasonal tick activity.  Wild rodent species are important in the ecology of many tick-borne diseases due to their ability to feed ticks and serve as reservoirs for pathogens.  Using a longitudinal study design, we explored the temporal dynamics and degree to which wild rodents are involved in tick-borne disease systems at a field site in east-central Texas.  For one full year, small mammals were live-trapped two nights per month and subjected to blood and ear biopsy collections.  All captured mammals were checked for the presence of ticks.  Data from 338 captures, representing 210 individuals, of four species (Peromyscus leucopus, Sigmodon hispidis, Reithrodontomys fulvescens, and Baiomys taylori) suggest that tick infestation prevalence was found to be low, with only 7 of 210, or 3.33% of individuals, parasitized across the year.  Peaks of larval and nymphal tick activity occurred in the fall, when Ixodes scapularis, Amblyomma americanum, A. maculatum, and Dermacentor variabilis, were found at the larval and nymphal life stages on 2 species of rodents.  Additionally adult A. maculatum and D. variabilis were also found through drag sampling.  All ear biopsies were tested for the presence of Borrelia species using genus-specific PCR primers followed by DNA sequencing for species and strain-level analysis.  B. burgdorferi was rare, with only 1 of 210 (0.48%) rodent ear biopsies testing positive.  However, rodent infection prevalence with the relapsing fever spirochete B. miyamotoi was relatively high, with 18 of 210 (8.57%) of individuals testing positive.  B. miyamotoi was recently identified a pathogen of human disease in North America and our work establishes that small rodents outside of Lyme disease endemic zones may be important reservoirs.