Figure 7.

Model for population dynamics of OspA and OspC during B. burgdorferi (Bb) transmission from ticks to mice. The model is based on the predominant Osp phenotypes observed in the different organs. See text for details of model. In brief, we propose that at early times of feeding (<53 hr) noninfectious bacteria that mainly produce OspA and others that produce neither Osp invade the salivary glands and host dermis in small numbers, but they fail to stably infect the mice. Stable transmission is initiated later (≥53 hr) when bacteria producing only OspC leave the gut. These infectious organisms clear OspC en route to the salivary glands and then enter the host dermis. In our model, from the heterogeneous population in the gut, only a subpopulation that is depleted of OspA is successfully transmitted to mice.