Abstract: [Objective] This study was conducted to investigate the prevalence of tick-borne spotted fever group Rickettsia （SFGR） on the body surface of cattle and sheep in Aksu Prefecture, Xinjiang Uygur Autonomous Region. [Method] A total of 574 ticks on the body surface of cattle and sheep were randomly collected from Aksu City （n=344）, Wensu County （n=93）, Xayar County （n=98） and Wushi County （n=39） in Aksu Prefecture. PCR assays targeting at Rickettsia outer membrane protein B gene （ompB） and surface cell antigen 1 gene （sca1） were utilized to detect the presence of Rickettsia and to determine the SFGR genotypes. The strong positive samples of the two genes were selected for sequencing. Phylogenetic trees were constructed by comparing the obtained sequences with the relevant gene sequences registered in the GenBank Database. The differences in Rickettsia infection rates in the ticks collected from the four regions were compared.[Result]The presence of 3 SFGR genotypes, Candidatus Rickettsia barbaria, Rickettsia sibirica and Rickettsia massiliae, were observed in the ticks on the body surface of cattle and sheep. The overall positive rate of Rickettsia in the tick samples was 15.16% （87/574）, with Wensu County having the highest positive rate of 23.66% （22/93）. Among the 3 detected SFGR genotypes, Candidatus Rickettsia barbaria was identified as the dominant species （Dr=44.83%, 39/87）. There were significant （P=0.001,χ²=15.834） differences in Rickettsia infection rate in the ticks among the four regions. [Conclusion]Aksu Prefecture is an endemic area for ticks and Rickettsia. It is advised to strengthen the prevention and control of tick and tick-borne diseases.

Key words: tick, Rickettsia, spotted fever group, genotype, sequence analysis