Artificial Infection of Ticks with Borrelia burgdorferi Using a Microinjection Method and Their Detection In Vivo...

Borrelia burgdorferi is maintained in nature by a tick-rodent infection cycle where it traverses and colonizes a variety of host and vector tissues. A tick-borne murine model has been developed to study Lyme disease in the laboratory, which has a substantial impact in advancing our knowledge of spirochete infectivity and pathogenesis. Here, we detail a microinjection-based method for rapid and efficient infection of ticks with B. burgdorferi. While laboratory generation of B. burgdorferi-infected nymphs via natural larval engorgement on infected hosts and subsequent molting could take several weeks to months, the microinjection-based infection procedure requires only a few hours to generate infected ticks and allows introduction of defined quantities of spirochetes, including mutant isolates that are attenuated for infection in mice and thus cannot be naturally acquired by ticks. We also describe a quantitative PCR-based protocol for the measurement of B. burgdorferi in tick and murine hosts targeting spirochete RNA that is highly efficient, reproducible, and a better surrogate of active infection.