Vascular clearance of Borrelia burgdorferi in rats

Radiolabeled Borrelia burgdorferi, the etiologic agent of Lyme disease, injected intravenously into rats are cleared from the vasculature within 1 h of injection. One low passage isolate showed trafficking between the circulation and possibly the vessel walls for the first 2 h after injection. All strains used were resistant to the effects of normal and heat-inactivated rat serum. During the first 2 h after injection, B. burgdorferi can be visualized in, and recovered from, the platelet-rich plasma. B. burgdorferi can adhere to both human and rat platelets in in vitro assays, but an in vivo association with these cells was not apparent. Similarly, none of the strains of B. burgdorferi used induced platelet aggregation. Removal from the circulation into the organs was measured in perfused rats by polymerase chain reaction and autoradiography and in non-perfused rats by organ cultures. These organisms invade organs (heart, kidneys, bladder, liver, spleen, brain) within 1-6 h after injection. Invasion of organs occurred in an apparent random manner; a large amount of radiolabel but no live organisms was excreted in the urine during the first 24 h, suggesting degradation of the inoculum.