Borrelia transfer by ticks during their life cycle. Studies on laboratory animals

Ticks of the species Ixodes ricinus were cultured in the laboratory. Yellow silver rabbits, gerbils and white mice served as blood hosts. Borrelia burgdorferi could be detected by means of an IFA test in homogenates of female ticks, their eggs as well as the respective larval and nymphal ticks. Blood infection of splenectomized gerbils and ordinary white mice or of ordinary white mice alone has been demonstrated after feeding of larval or nymphal ticks on them, respectively. Spirochetemia started 5 to 8 days after feeding and lasted for ca 3 weeks. Two distinct peaks in the cell count of spirochetal organisms per ml blood plasma could be observed on days 11-13 (5 X 10(5) to 2 X 10(6) cells/ml) and 17-19 (10(5) cells/ml), regardless whether splenectomized gerbils or white mice were used. The results display that B. burgdorferi is vertically from the female ticks to their eggs and transstadially transmitted. The transmission-rate from larval to nymphal ticks is 100%. These findings show the tick itself as a main reservoir of B. burgdorferi. The established mouse-model appears to be a useful tool to detect Borrelia carrying ticks.