Abstract: ObjectiveTo investigate rodents.natural infection of vOrientia tsutsugamushi(Ot)in Tai'an area of Shandong,China.MethodsThe Ot-Sta56KDa gene of ro dents captured from Tai'an was identified by nested poly merase chain reaction(nPCR).Positive samples were sequenced,and the DNA sequences were compared with nucleotide sequences of Ot registered in GenBank for sequence homology analysis.Phylogenetic analysis about the Ot in Tai'an and some published sequences was carried out with Neighbor-joining method by MEGA3.1 software.ResultsAtotal of 68 ro dents were captured in Tai'an area,including 24 Apodemus agrarius,34 Rattus norvegicus and 10 Mus musculus.The overall positive rate of rodents with infection of Ot was 5.88%.There was no significant difference in infection rates among the rodents species(Fisher χ²=4.714,P=0.062).In addition,3 embryos without Ot infection of rodents were captured.Comparing with the sequences of Ot registered in GenBank,the Ot-Sta56 nucleotide sequences of 08Pand 53Pboth shared 99.77% of homology with Sdu-1 strain,95.98% with Tag uchi and Oishi strains,and 95.74% with Kanda and Kaw asaki str ains.The nucleot ide sequence of 55P shared 86.27% of homology with TA 686 str ain founded in Thailand,and the sequence of 56P shared 77.11% homology with TA 686 strain.Phylogenetic analysis showed that 08P and 53P were in the same branch with Sdu1 strain,and 55P and 56P were in the same branch with TA686 strain.ConclusionThis study indicated that Ot infection was presented in rodents from Tai'an.The genotypes of Ot were complex in Tai'an,with some were similar to Kawasaki strain and others were similar to TA686 strain in Thailand.