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During May 1996, field surveys on
Lyme disease spirochetes were conducted in Beijing, Shenyang, Fushun, and Inner Mongolia in northeastern China. The ticks collected consisted of 3 genera and 12 species. Of these, Ixodes persulcatus was dominant in sun-exposed vegetation in forests in Inner Mongolia; 57 Borrelia strains (55/123 unfed adults and 2/5 immature stages fed on a rodent) were obtained from this tick by BSK culture. Additionally, 2/2 Apodemus peninsulae were positive. Ixodes nipponensis, Ixodes pavlovskyi, Haemaphysalis douglasi, and Haemaphysalis megaspinosa, newly recorded in China, and other Haemaphysalis spp. were all negative for Borrelia. Based on a polymerase chain reaction restriction fragment length polymorphism analysis of the 45 strains successfully subcultured, these were classified as 29 Borrelia garinii and 16 Borrelia afelii. These strains seemed to be more closely related to Japanese strains in genetic features than to those from Europe. The result of sodium dodecyl sulfate-polyacrylamide gel electrophoresis suggested more diversity in both genospecies, but Borrelia burgdorferi sensu stricto was not found.