Abstract: o determine the ability of Ixodes sinensis Teng, Haemaphysalis yeni Toumanoff and H. qinghaiensis Teng to transmit Borrelia garinii as potential vector of Lyme disease in South China, transstadial transmission of the spirochetes by the three species was studied in the laboratory. Results showed that the three tick species could acquire active Lyme spirochetes by feeding on infected KM mice. However, only I. Sinensis could maintain active spirochetes during molting, with subsequent developing stages infectious to normal KM mice. H. yenI　and H. qinghaiensis maintained spirochetes not longer than the period of blood digestion; after molting, no spirochetes were detected in the both species. Therefore, the possibility of either H. yeni or H. qinghaiensis to be the vector of Lyme disease was small. The successful transmission of B. garinii in I. Sinensis during both larva to nymph and nymph to adult periods in the laboratory indicated that it might be the potential vector of Lyme disease in South China.

Key words: Ixodes sinensis, Haemaphysalis yeni, Haemaphysalis qinghaiensis; Lyme diseas e, transmission transstadially, animal model, South China