Multilocus Sequence Typing and DNA Similarity Analysis Implicate Borrelia valaisiana-Related sp. Isolated in Japan Is Distinguishable from European B. valaisiana

抄録

Lyme disease Borrelia spp. are transmitted by Ixodes ticks, and more than 10 species of borreliae have been identified around the world. Recently another Borrelia sp. has been reported in Asia (Japan, Korea, China, Taiwan and Thailand) as Borrelia valaisiana-related sp. In the present study, we obtained and genetically characterized 19 B. valaisiana-related sp. strains from mammals and ticks. Genetic analyses showed that the Borrelia strains were distinct from B. valaisiana found in Europe. Multilocus sequencing typing revealed that these Borrelia isolates formed a monophyletic group with B. yangtze strains in China. Some of strains were isolated from the bladders of small mammals, and also two strains were experimentally confirmed to be infectious to C3H/HeN mice. We observed that the Borrelia sp. was maintained in Ixodes granulatus tick after molting. These results suggested that small mammals and I. granulatus were possible reservoir hosts and vector tick for the Borrelia sp., respectively. B. valaisiana, originally found in Europe, was transmitted mainly by I. ricinus, and birds were mainly thought to be reservoir hosts. Our results suggested Japanese isolates of B. yangtze (formerly B. valaisiana-related sp.) were distinguishable from B. valaisiana according to the reservoir host and its vector tick. In this study, we also deposited borrelia strain Okinawa-CW62 to bioresource centers as a reference strain of the B. yangtze (=DSM 24625, JCM 17189).