Plastic tubes

Ornithodoros hermsi ticks used in this study were from a colony maintained at the RML that was established with a single, uninfected, fertilized female from Siskiyou County, California (collected October 29, 1997). Ticks were kept either in groups in 15 or 50 mL plastic tubes (Corning Inc., Corning, NY) or individually in 1.5 mL snap-cap micro-centrifuge tubes. The tubes were ventilated with holes in the cap and filter paper was placed inside to absorb fluids. Tick tubes were kept in closed glass desiccator jars at 22–25°C, 85% relative humidity (Winston and Bates, 1960 ) with ambient light. B. hermsii DAH was used for the tick acquisition and transmission experiments (see below). Spirochetes were grown in mBSK-c medium (Barbour, 1984 (link); Battisti et al., 2008 ), and 5×10⁵ cells were injected intraperitoneally into a mouse (Mus musculus) (RML strain; a closed colony used at RML since 1937 that originated from outbred Swiss-Webster mice). After 2 – 4 days of infection, the spirochetemia in the mouse became ~ 10⁶ cells per ml or greater, and ticks were fed to repletion. These infected ticks were used either immediately (as hosts) for the acquisition experiments, or were allowed to molt and then feed (as parasites) in the transmission experiments (see below).