Objective To understand the infection and genotypes of Borrelia burgdorferi carried by free-living ticks in Arxan,Inner Mongolia,China,and to provide a basis for local prevention and control of Lyme disease.Methods From May 2020 to May 2021,the drag-flag method was used to collect free-living ticks in Arxan.Tick species were identified by morphology and specific 16S rDNA gene sequencing.Genomic DNA was extracted from 113 randomly selected ticks.Nested-PCR targeting the 5S-23S rRNA intergenic spacer region was used to detect B.burgdorferi,and sequence analysis was performed to determine the genotypes of B.burgdorferi in ticks.The B.burgdorferi carried by 102 Ixodes persulcatus were isolated and cultured in BSK II medium.Multilocus sequence analysis (MLSA) was used to genotype the isolates.Results A total of 295 free-living ticks were collected,which were dominated by I. persulcatus(282/295,95.59%),followed by Dermacentor silvarum(13/295,4.41%).PCR detection of 113 ticks showed that 24 of 100 I. persulcatus carried B. burgdorferi,and the infection rate was 24.00%.Of these,17 were infected with B.garinii(17/24,70.83%),and 7 were infected with B.afzelii (7/24,29.17%).B.burgdorferi was not detected in 13 D.silvarum.Two strains of B. burgdorferi were isolated from the 102 I. persulcatus,which were identified as B. garinii through MLSA.Conclusion The free-living ticks in Arxan in May were dominated by I. persulcatus.The infection rate of B. burgdorferi in I. persulcatus was 24.00%,and the infection was caused by B. garinii and B. afzelii.Two B. garinii strains were isolated from ticks,which suggests that natural infection of spirochetes of Lyme disease was present in Arxan of Inner Mongolia.Local government should pay attention to the risk of B. burgdorferi infection as a causative agent of Lyme disease,monitor the populations,vector ticks,and hosts,and establish a system for the scientific prevention and control of Lyme disease.
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