Zhu Wen-Jie, Ye Run-Ze, Tian Di, Wang Ning, Gao Wan-Ying, Wang Bai-Hui, Lin Zhe-Tao, Liu Ya-Ting, Wang Yi-Fei, Zhu Dai-Yun, Sun Yi, Shi Xiao-Yu, Shi Wen-Qiang, Jia Na, Jiang Jia-Fu, Cui Xiao-Ming, Liu Zhi-Hong, Cao Wu-Chun
State Key Laboratory of Pathogen and Biosecurity, Academy of Military Medical Sciences, Beijing, P.R. China.
Department of Emergency Medicine, Qilu Hospital of Shandong University, Jinan, Shandong, P.R. China.
PLoS Negl Trop Dis. 2025 Jan 2;19(1):e0012729. doi: 10.1371/journal.pntd.0012729. eCollection 2025 Jan.
Tick-borne infectious diseases caused by the spotted fever group Rickettsia (SFGR) have continuously emerging, with many previously unidentified SFGR species reported. The prevalence of SFGRs in northwestern China remains unclear. This study aimed to examine the prevalence of SFGRs and Anaplasma species by analyzing tick samples collected from the Ningxia region.
During 2022-2023, ticks were collected from Ningxia, northwestern China, and screened using PCR to amplify target genes (16S rRNA, gltA, ompA and groEL). The amplicons were confirmed by Sanger sequencing. Single-gene sequences and concatenated sequences were used to infer phylogenetic relationships for identifying Rickettsia species.
Out of the 425 DNA samples, a total of 210 samples tested positive for SFGRs in ticks from Ningxia, China, with a relatively high positive rate of 49.4% (210/425). Eight spotted fever group rickettsiae and one Anaplasma species were identified and characterized, including Rickettsia raoultii (102, 24.0%), R. aeschlimannii (65, 15.3%), R. sibirica (12, 2.8%), R. slovaca (4, 0.9%), R. heilongjiangensis (1, 0.2%), Cadidatus Rickettsia hongyuanensis (4, 0.9%), Ca. R. jingxinensis (11, 2.6%), Ca. R. vulgarisii (11, 2.6%) and Anaplasma ovis (98, 23.1%). The positive rate of bacterial species ranged from 0.2% to 24.0%. Interestingly, one novel Rickettsia species, provisionally named "Candidatus Rickettsia vulgarisii", was detected in Argas ticks from Zhongwei city, which suggests the possibility of local transmission to other areas through birds. Genetic and phylogenetic analysis based on the 16S rRNA, gltA, ompA, and 17kDa genes indicated that it was divergent from all known SFG Rickettsia species but mostly related to R. vini. Different SFGR species were associated with specific tick species or genera. In addition, Anaplasma ovis was detected in two Dermacentor species, and co-infection with SFGRs was observed in 14.6% (62/425) of samples.
This study describes the prevalence and diversity of SFGRs in ticks from Ningxia for the first time by direct detection, reveals that Rickettsia diversity related to tick species. This data suggests that surveillance for tick-borne SFGR infections among human populations should be enhanced in this region, and further investigations on their pathogenicity to humans and domestic animals are still needed.
由斑点热群立克次体（SFGR）引起的蜱传传染病不断出现，有许多此前未被鉴定的SFGR物种被报道。中国西北地区SFGR的流行情况仍不清楚。本研究旨在通过分析从宁夏地区采集的蜱样本，检测SFGR和无形体属物种的流行情况。
在2022年至2023年期间，从中国西北部的宁夏采集蜱，并使用PCR扩增靶基因（16S rRNA、gltA、ompA和groEL）进行筛查。扩增产物通过桑格测序进行确认。单基因序列和串联序列用于推断系统发育关系以鉴定立克次体物种。
在425个DNA样本中，来自中国宁夏的蜱样本中共有210个样本SFGR检测呈阳性，阳性率相对较高，为49.4%（210/425）。鉴定并表征了8种斑点热群立克次体和1种无形体属物种，包括拉乌尔蒂立克次体（102个，24.0%）、埃氏立克次体（65个，15.3%）、西伯利亚立克次体（12个，2.8%）、斯洛伐克立克次体（4个，0.9%）、黑龙江立克次体（1个，0.2%）、候选宏远立克次体（4个，0.9%）、候选静新立克次体（11个，2.6%）、候选普通立克次体（11个，2.6%）和绵羊无形体（98个，23.1%）。细菌物种的阳性率在0.2%至24.0%之间。有趣的是，在中卫市的软蜱中检测到一种新的立克次体物种，暂命名为“候选普通立克次体”，这表明存在通过鸟类向其他地区局部传播的可能性。基于16S rRNA、gltA、ompA和17kDa基因的遗传和系统发育分析表明，它与所有已知的斑点热群立克次体物种不同，但与维尼立克次体关系最为密切。不同的SFGR物种与特定的蜱物种或属相关。此外，在两种 Dermacentor 属蜱中检测到绵羊无形体，并且在14.6%（62/425）的样本中观察到与SFGR的共感染。
本研究首次通过直接检测描述了宁夏蜱中SFGR的流行情况和多样性，揭示了立克次体多样性与蜱物种有关。这些数据表明该地区应加强对人群中蜱传SFGR感染的监测，并且仍需要进一步研究它们对人类和家畜的致病性。
