Vertical transmission of Borrelia turicatae (Spirochaetales: Borreliaceae) by autogenously reproducing Ornithodoros turicata (Ixodida: Argasidae) female naturally infected with the spirochetes

Abstract

Ornithodoros turicata is a vector of relapsing fever (RF) spirochetes in North America and transmits Borrelia turicatae to a variety of vertebrate hosts. The remarkably long lifespan of O. turicata and its ability to maintain spirochetes horizontally (between life stages) and vertically to progeny promotes the perpetuation of B. turicatae in nature. Nevertheless, the reproductive biology of O. turicata is poorly understood. In this report, we collected ticks from a park within a neighborhood of Austin, Texas. They were reared to adulthood and male ticks were individually housed with females. We observed autogenous reproduction by the ticks and further investigated vertical transmission of B. turicatae by quantifying filial infection rates in a cohort of progeny ticks. These results indicate that O. turicata transovarially transmits B. turicatae during autogenous reproduction and further signify the tick as a natural reservoir of the spirochetes. ImportancePrevious research has implicated Ornithodoros ticks, including Ornithodoros turicata, as long-term reservoirs of relapsing fever (RF) spirochetes. Considering the ticks long lifespan and their efficiency in maintaining and transferring spirochetes within the population, the infection could persist in a given enzootic focus for decades. However, little is known about the relative importance of horizontal and vertical transmission routes in the persistence and evolution of RF Borrelia. Our observations on the reproductive biology of O. turicata in the absence of vertebrate hosts indicate an additional mechanism by which B. turicata can be maintained in the environment. This work establishes the foundation for studying O. turicata reproduction and spirochete-vector interactions, which will aid in devising control measures for Ornithodoros ticks and RF spirochetes.