Molecular epidemiology of Borrelia burgdorferi sensu lato in the East Asia.

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We conducted a survey to isolate Borrelia from ticks and wild rodents in far eastern Russia, China, and Korea between 1996 and 1998. These isolates were characterized and identified by various molecular typing methods and sequencing analysis. In northeastern China and far eastern Russia, Ixodes persulcatus was a prominent vector and carried B. afzelii and B. garinii. The far eastern type of B. garinii was the dominant species in this area but was not found in Europe, similar to the distribution seen in Hokkaido, Japan and northern part of the South Korea. The finding indicate the transmission of Borrelia between Japan, and far eastern Russia and northeastern China. However, one difference should be point out ; in northern part of South Korea, I. nipponensis has the ability to transmit B. afzelii and B. garinii. Interestingly, isolates from the ticks collected in the southern tip of the Korean Peninsula were identified as B. valaisiana.In southern China beside the Yangze river valley, Borrelia was isolated from I. granulatus, I. ovatus, and Apodemus agrarius and Niviventer species. Most isolates were identified as B. valaisiana and were similar to the isolates from Korea. However, the group of Borrelia has different type of ospA in comparison with those of European B. valaisiana, indicating that the Borrelia species is divergent. Furthermore, some isolates from Sichuan and Anhui provinces were unique and 16S rRNA gene sequences of these Borrelia species showed similarity values ranging from 99.8 to 100% and clustered with each other on phylogenetic tree, but they were less than 99.0 with those of previously described Lyme disease Borrelia species. Therefore, we speculated that the B. valaisiana found in I. ricinus in Europe was adapted to the tick I. granulatus in central China, I. nipponensis in the southern tip of Korea, and I. columnae in Japan. Furthermore, unique Borrelia species are present in central China.