Borrelia burgdorferi strain and host sex influence pathogen prevalence and abundance in the tissues of a laboratory rodent host

Experimental infections with different pathogen strains give insight into pathogen life history traits. The purpose of our study was to compare variation in tissue infection prevalence and spirochete abundance among strains of B. burgdorferi in a rodent host (Mus musculus, C3H/HeJ). Male and female mice were experimentally infected via tick bite with one of 12 strains. Ear tissue biopsies were taken at days 29, 59, and 89 post-infection (PI), and 7 tissues were collected at necropsy. The presence and abundance of spirochetes in the mouse tissues were measured by qPCR. To determine the frequencies of our strains in nature, their MLSTs were matched to published datasets. For the infected mice, 56.6% of the tissues were infected with B. burgdorferi. The mean spirochete load in the mouse necropsy tissues varied 4.8-fold between the strains with the lowest and highest values. The mean spirochete load in the ear tissue biopsies decreased rapidly over time for some strains. The percentage of i...