Molecular Epidemiology Investigation Of Borrelia Burgdorferi In Some Areas Of Xinjiang

Lyme disease is a naturally occurring infectious disease of human and animal origin caused by Borrelia burgdorferi.Ticks are an important vector for the transmission of the disease,and rodents are its main host animals.Studies has confirmed the existence of multiple natural epidemic sites of Lyme disease in Xinjiang.Between 2019 and 2021,a total of 423 samples,including 276 ticks（more than 1 000 ticks）and147 rodents,were collected from seven sites in Xinjiang,including Alashankou,Jimsar,Yili region,Usu,Qinghe,Yutian,and Hutubi.Kidney and bladder tissues of ticks and rodents were ground into homogenates,inoculated through 0.22μm filter membranes in BSK-H medium and incubated at 33°C in a 5%concentration CO₂incubator,and cultured by passaging and purification to obtain four strains of the Lyme disease pathogen B.burgdorferi spirochetes belonging to three genotypes,namely two B.bavariensis genotypes,one B.garinii genotype,and one strain is Borrelia burgdorferi undetermined genotype.To improve the accuracy and comprehensiveness of the test,two methods,Real-time PCR（16Sr RNA）and Nested PCR（5S-23Sr RNA spacer region）,were applied to detect B.burgdorferi spirochetes in 423samples in this study.The results showed that the positive rate of the Real-time PCR method was 8.51%（36/423）for ticks and rodents carrying Borrelia burgdorferi in Xinjiang;the positive rate was 9.22%（39/423）for the Nested PCR method.There was basically no significant difference between the results of the two methods.The Nested PCR amplification products based on the fragment of 5S-23S r RNA spacer region of B.burgdorferi were analyzed by gene sequence comparison,and the data analysis results showed that there were four main genotypes of B.burgdorferi prevalent in Xinjiang,with B.garinii genotypes accounting for 40.63%（13/32）,B.afzelii genotypes accounted for 12.5%（4/32）,B.bavariensis genotypes accounted for 9.38%（3/32）,Borrelia burgdorferi undetermined genotype accounted for37.50%（12/32）.The phylogenetic tree of 32 samples was constructed based on the 5S-23S sequences of NJ algorithm,and the results showed that,the phylogenetic tree mainly belonged to 2 large branches,11 were clustered on one branch,and 9 of them were phylogenetically close to B.garinii group and B.bavariensis,with Russia,Siberia,Taipei,etc.The genetic evolutionary relationship of two strains is close to that of B.burgdorferi sensu stricto in the same branch and close to that of B.burgdorferi s.s B31 in the USA;21strains are clustered on another branch and their genetic evolutionary relationship is close to that of B.garinii mgds in northeastern China.The genetic diversity of spirochetes in Xinjiang is rich.As Xinjiang was the natural source of Lyme disease,it was of great practical significance to investigate the infection and genotyping of B.garinii in vectors and hosts to predict the risk of Lyme disease in different regions,in order to provide a scientific basis for the prevention and control of Lyme disease in Xinjiang.