Seroprevalence for the tick-borne relapsing fever spirochete Borrelia turicatae among small and medium sized mammals of Texas.

Brittany A Armstrong,Ken Waldrup,Pete D Teel,Aparna Krishnavajhala,Edward Wozniak,Taylor G Donaldson,Job E Lopez,Kristy O Murray,Carson Phillips,William Boyle,Alexander Kneubehl,Kristen Hollywood,Hannah K Wilder,Melissa J Caimano

doi:10.1371/journal.pntd.0006877

Abstract

BackgroundIn low elevation arid regions throughout the southern United States, Borrelia turicatae is the principal agent of tick-borne relapsing fever. However, endemic foci and the vertebrate hosts involved in the ecology of B. turicatae remain undefined. Experimental infection studies suggest that small and medium sized mammals likely maintain B. turicatae in nature, while the tick vector is a long-lived reservoir.Methodology/principal findingsSerum samples from wild caught rodents, raccoons, and wild and domestic canids from 23 counties in Texas were screened for prior exposure to B. turicatae. Serological assays were performed using B. turicatae protein lysates and recombinant Borrelia immunogenic protein A (rBipA), a diagnostic protein that is unique to RF spirochetes and may be a species-specific antigen.Conclusions/significanceSerological responses to B. turicatae were detected from 24 coyotes, one gray fox, two raccoons, and one rodent from six counties in Texas. These studies indicate that wild canids and raccoons were exposed to B. turicatae and are likely involved in the pathogen’s ecology. Additionally, more work should focus on evaluating rodent exposure to B. turicatae and the role of these small mammals in the pathogen’s maintenance in nature.

Highlights

Tick-borne relapsing fever (RF) is primarily caused by spirochetes in the genus Borrelia and the pathogens are transmitted when infected Ornithodoros ticks feed on a competent vertebrate host
In arid regions of the southern United States and Mexico, tick-borne relapsing fever is primarily caused by Borrelia turicatae
In the United States and Mexico, there is an association between Ornithodoros ticks and RF spirochete species where Ornithodoros hermsi, Ornithodoros parkeri, Ornithodoros turicata, and Ornithodoros talaje transmit Borrelia hermsii, Borrelia parkeri, Borrelia turicatae, and Borrelia mazzottii, respectively [1]

Summary

Introduction

Tick-borne relapsing fever (RF) is primarily caused by spirochetes in the genus Borrelia and the pathogens are transmitted when infected Ornithodoros ticks feed on a competent vertebrate host. In the United States and Mexico, there is an association between Ornithodoros ticks and RF spirochete species where Ornithodoros hermsi, Ornithodoros parkeri, Ornithodoros turicata, and Ornithodoros talaje transmit Borrelia hermsii, Borrelia parkeri, Borrelia turicatae, and Borrelia mazzottii, respectively [1]. These tick species involved in human disease are distributed in varying ecological niches. In low elevation arid regions throughout the southern United States, Borrelia turicatae is the principal agent of tick-borne relapsing fever. Experimental infection studies suggest that small and medium sized mammals likely maintain B. turicatae in nature, while the tick vector is a long-lived reservoir

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