Molecular biological identification of ticks and tick-borne pathogens in Yadong,Tibet / 中国人兽共患病学报

ABSTRACT

This study was aimed at identifying species of ticks and investigating infections with tick-borne pathogens a-mong people in Yadong,Tibet.The total of 23 ticks(Ixodes and Haemaphysalis)collected from livestock in Yadong,Tibet in July 2021,the gene sequences of cytochrome oxidase subunitⅠ(COX Ⅰ),mitochondrial 16S ribosomal DNA(16S rDNA)and mitochondrial 12S ribosomal DNA(12S rDNA)were identi-fied on the basis of molecular biology classification.The gene sequences of spotted fever group rickettsia(SFGR),Borrelia burgdorferi,Francisella tularensis and Coxiella burnetii in ticks were amplified by PCR and sequenced,and phylogenetic ana-lyses were performed.In addition,184 serum samples collected from Yadong in 2021 were screened for antibodies to Lyme dis-ease,Q fever,spotted fever,and tularemia by ELISA,and infections with tick-borne pathogens in Yadong were comprehen-sively analyzed.The ticks(Ixodes)collected in Yadong,Tibet,were grouped into two categories.The COX Ⅰ,16S rDNA,and 12S rDNA gene sequences of the ticks had 99.5％,97.57％,and 99.12％ similarity,respectively,to those of Ixodes nuttallia-nus in GenBank.The similarities between the COX Ⅰ and 16S rDNA gene sequences of another Ixodes tick species and the COXⅠ and 16S rDNA gene sequences of Ixodes ovatus in GenBank were 88.29％ and 95.75％,respectively.The similarity between the COX Ⅰ,16S rDNA,and 12S rDNA gene sequences of Haemaphysalis ticks and those of Haemaphysalis Tibet in GenBank were 96.04％,96.17％,and 97.47％,respectively.The sequence amplification results for Borrelia burgdorferi,Francisella tularensis,and Coxsiella burnetii in 23 ticks were negative,whereas gltA gene amplification of spotted fever group Rickettsia in 23 ticks was positive.The similarity of gltA gene sequences with respect to those of Candidatus Rickettsia tarasevichiae,Rickettsia raoultii,Rickettsia canadensis,and a Rickettsia endosymbiont of Eucalyptus brunneri in GenBank was 96.77％,96.76％,95.35％,and 95.35％,respectively.Among 184 serum samples from Yadong,the positivity rates of Lyme disease,Q fever,spotted fever,and tularemia were 6.52％,12.50％,8.70％,and 10.87％,respectively.These results indicated that the 23 parasitic ticks collected in Yadong,Tibet,in July 2021 were Ixodes nuttallianus,Ixodes ovatus and Haemaphysalis ti-betensis,and 23 ticks were infected with SFGR.Lyme disease,Q fever,spotted fever,and tularemia infection were prevalent in the population of Yadong.Therefore,efforts to control tick-borne diseases must be strengthened.