Doctor of Philosophy (PhD)


Veterinary Medical Sciences - Pathobiological Sciences

Document Type



Lyme borreliosis is an emergent threat to human health. It is estimated that 300,000 cases of Lyme disease are diagnosed annually in the United States. In recent years, non-traditional areas are starting to report more and more cases. While much research has gone into the tick and bacteria responsible for the disease, frequently new Borrelia species are being described and implicated in human illness. These species often go unstudied, and their threat to human health is not known. In the hopes of closing knowledge gaps on Lyme borreliosis in the US, we surveyed a non-endemic state, Louisiana, for Lyme Borrelia in ticks and mammals. We also assessed the potential for a second North American Lyme Borrelia species to cause mammalian disease by examining the infectivity and immune response of a non-B. burgdorferi sensu stricto North American isolate, Borrelia bissettii, in a murine model. Similarities between B. burgdorferi ss and B. bissettii prompted us to assess the ability for Ixodes scapularis to acquire and transmit B. bissettii to susceptible animals. Our research uncovered evidence for an enzootic cycle of Borrelia burgdorferi ss at a site in Louisiana between small mammals and Ixodes scapularis ticks. This, combined with broader evidence of multiple tick-borne pathogens in human biting ticks, highlights the need for tick-borne disease surveillance in areas not traditionally considered endemic. Borrelia bissettii may play a role in human disease in the US, especially in areas where B. burgdorferi ss is not common. We describe similarities between B. bissettii and B. burgdorferi ss murine infection; moreover, current Lyme diagnostic test could not differentiate infections. While I. scapularis could acquire B. bissettii spirochetes from infected mice, they existed at lower burdens compared to B. burgdorferi ss. Ixodes scapularis was also unable to transmit B. bissettii infection to susceptible animals, incriminating a different tick vector in the eastern and southern US. These data support the need for continued work on the Lyme Borrelia species as a whole, especially in non-traditional areas and on understudied organisms.



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Committee Chair

Liang, Fang-Ting