Efficiency of experimental infection of Ixodes ricinus ticks with Borrelia burgdorferi spirochetes

Feeding of an ixodid tick on a Borrelia-infected vertebrate is the natural route of tick infection. To obtain a cohort of nymphs with a high prevalence of infection, the immersion of Ixodes ricinus larvae in the suspension of B. burgdorferi sensu stricto spirochetes was used. Immersed larvae fed on C3H mice until full engorgement, molted to nymphs and 9 of 10 nymphs were shown to be infected by PCR with specific primers. Specific antibodies in the sera of the mice, on which either immersion-infected larvae or infected nymphs had engorged, were not detected. However, nymphs molted from immersed larvae were able to infect naïve mice, and all the resulting 10 adults were infected.