Abstract: Objective　To investigate the prevalence of spotted fever group rickettsiae (SFGR) infections in free⁃living ticks and among high⁃risk populations in the southern margin of the Gurbantunggut Desert, Xinjiang Uygur Autonomous Region, so as to provide insights into tick⁃borne diseases prevention and control in this region. Methods　Free⁃living ticks were collected from five counties (cities) in the southern margin of the Gurbantunggut Desert, Xinjiang Uygur Autonomous Region. Tick species were identified by morphology combined with mitochondrial cytochrome c oxidase subunit Ⅰ (COI) gene analysis. Four target gene fragments of Rickettsia were amplified using a nested PCR assay, including outer membrane protein B (ompB), 17⁃kDa common surface antigen protein (17kDa), surface cell antigen 1 (sca1), and surface cell antigen 4 (sca4) genes, to detect the prevalence of SFGR infections in tick samples. Positive PCR amplification products were purified, sequenced, and subjected to sequence alignment, and phylogenetic trees were created using the neighbor⁃joining (NJ) method. Serum samples were collected from individuals at a high risk of tick exposure from six counties (cities, districts) in the southern margin of the Gurbantunggut Desert, Xinjiang Uygur Autonomous Region, and serum levels of anti⁃R. sibirica IgG antibodies were detected among these individuals using indirect immunofluorescence assay (IFA) and statistically analyzed. Results　A total of 287 free⁃living ticks were collected, and all were identified as Hyalomma asiaticum. The overall prevalence of SFGR infection was 78.40% (225/287) in tick samples, and five Rickettsia species were characterized, including R. sibirica, which shared 99.81% (515/516) sequence homology with the strain detected in Dermacentor sinicus from China; R. massiliae, which shared 99.80% (509/510) sequence homology with the strain detected in Rhipicephalus sanguineus from Ethiopia; R. raoultii, which shared 100.00% (516/516) sequence homology with the strain detected in Hyalomma asiaticum from Xinjiang Uygur Autonomous Region in China; R. africae, which shared 100.00% (524/524) sequence homology with the strain detected in Amblyomma splendidum from Ethiopia; and Candidatus Rickettsia barbariae, which shared 99.80% (499/500) sequence homology with the strain detected in steppe polecats from Xinjiang Uygur Autonomous Region in China, with R. sibirica (33.80% detection rate, 97/287) and R. raoultii (33.10%, 95/287) as dominant species. A total of 1 489 serum samples were collected from individuals at a high risk of tick exposure, and the seroprevalence of anti⁃R. sibirica IgG antibodies was 30.83% (459/1 489). There were no significant differences in the seroprevalence in terms of genders ([χ2] = 2.23, P > 0.05) or age groups ([χ2] = 6.45, P > 0.05); however, there was a region⁃specific seroprevalence rate of anti⁃R. sibirica IgG antibodies ([χ2] = 16.05, P < 0.05). Pairwise comparisons showed lower seroprevalence rate of anti⁃R. sibirica IgG antibodies among high⁃risk individuals in Midong District of Urumqi City (22.27%, 53/238) than in Wujiaqu City (34.70%, 93/268) and Manas County(37.55%, 98/261) (both P values < 0.05); however, they were not significantly different from those in the other regions (all P values > 0.05). Conclusions　Multiple SFGR species are detected in H. asiaticum ticks sampled from the southern margin of the Gurbantunggut Desert, Xinjiang Uygur Autonomous Region, where there is a potential risk of local transmission of spotted fever rickettsiosis.

Key words: Tick, Spotted fever group rickettsiae, High?risk population, Epidemiology, Phylogenetic evolution, Gurbantunggut Desert, Xinjiang Uygur Autonomous Region

摘要： 目的　对新疆维吾尔自治区古尔班通古特沙漠南缘地区游离蜱和高风险人群斑点热群立克次体（spotted fever group rickettsiae，SFGR）感染情况进行调查，为该地区蜱传疾病防控提供参考。方法　在新疆维吾尔自治区古尔班通古特沙漠南缘地区5个县（市）采集游离蜱，通过形态学结合线粒体细胞色素c氧化酶亚基Ⅰ（cytochrome c oxidase subunit Ⅰ，COI）基因分析确定蜱种。采用巢式PCR法扩增立克次体外膜蛋白B（outer membrane protein B，ompB）、17 kDa共同表面抗原（17⁃kDa common surface antigen protein，17kDa）基因以及表面细胞抗原1（surface cell antigen 1，sca1）、表面细胞抗原4（surface cell antigen 4，sca4）基因4种目的基因片段，以检测蜱虫样本SFGR携带情况；同时对扩增阳性产物进行纯化、测序、比对分析，采用邻接法构建系统发育树。采集该沙漠南缘地区6个县（市、区）蜱暴露高风险人群血清样本，采用间接免疫荧光法（indirect immunofluorescence assay，IFA）检测上述人群中抗西伯利亚立克次体IgG抗体水平，并进行统计分析。结果　本研究共采集287只游离蜱，均为亚洲璃眼蜱（Hyalomma asiaticum），SFGR总感染率为78.40%（225/287）；共检出5种立克次体，其中西伯利亚立克次体（Rickettsia sibirica）与我国中华革蜱中检出株同源性为99.81%（515/516），马赛立克次体（R. massiliae）与埃塞俄比亚血红扇头蜱中检出株同源性为99.80%（509/510），劳氏立克次体（R. raoultii）与我国新疆维吾尔自治区亚洲璃眼蜱中检出株同源性为100.00%（516/516），非洲立克次体（R. africae）与埃塞俄比亚彩饰钝眼蜱中检出株同源性为100.00%（524/524），暂定巴布瑞克立克次体（Candidatus R. barbariae）与我国新疆维吾尔自治区虎鼬中检出株同源性为99.80%（499/500）。西伯利亚立克次体和劳氏立克次体为优势种，游离蜱感染率分别为33.80%（97/287）和33.10%（95/287）。共采集1 489例蜱暴露高风险人群血清样本，抗西伯利亚立克次体IgG抗体阳性率为30.83%（459/1 489）；不同性别、年龄组人群抗体阳性率差异无统计学意义（[χ2] = 2.23、6.45，P均> 0.05）；不同地区高风险人群抗体阳性率差异有统计学意义（[χ2] = 16.05，P < 0.05），其中乌鲁木齐市米东区血清阳性率［22.27%（53/238）］低于五家渠市［34.70%（93/268）］和玛纳斯县［37.55%（98/261）］（P均< 0.05），其余地区阳性率差异均无统计学意义（P均> 0.05）。结论　新疆维吾尔自治区古尔班通古特沙漠南缘地区的亚洲璃眼蜱广泛携带多种蜱传斑点热群立克次体，且蜱暴露高危人群血清学结果提示该地区存在斑点热本地传播的潜在风险。

关键词: 蜱, 斑点热群立克次体, 高危人群, 流行病学, 种系进化, 古尔班通古特沙漠, 新疆维吾尔自治区