Department of Preventive Veterinary Medicine, College of Veterinary Medicine, Northwest A&F University, Yangling, Shaanxi, China.
Scientific Observing and Experimental Station of Veterinary Pharmacology and Diagnostic Technology, Ministry of Agriculture, Yangling, Shaanxi, China.
Transbound Emerg Dis. 2019 Jul;66(4):1587-1596. doi: 10.1111/tbed.13184. Epub 2019 Apr 11.
Spotted fever group (SFG) rickettsiae are important causative agents of (re)emerging tick-borne infectious diseases in humans, and ticks play a key role in their maintenance and transmission. In this study, hard ticks were collected from five sampling sites in North China in 2017 and 2018. Of them, Haemaphysalis longicornis, Rhipicephalus microplus and Dermacentor nuttalli were collected from livestock (sheep and goats) and the vegetation, Hyalomma asiaticum from sheep, goats and camels, and Hyalomma marginatum from sheep and goats. The SFG rickettsiae were identified in these ticks by amplifying the partial rrs and complete 17-kDa genes, with an overall infection rate of 52.9%. In addition, the nearly full-length rrs and gltA and partial ompA genes were recovered to classify the species of SFG rickettsiae further. Phylogenetic analysis revealed the presence of three human pathogenic species in Hy. asiaticum, Hy. marginatum, Ha. longicornis and De. nuttalli, including two cultured ones (Rickettsia raoultii and Rickettsia aeschlimannii) and one uncultured (Candidatus R. jingxinensis). Furthermore, partial groEL gene was also obtained, and phylogenetic trees were also reconstructed to better understand the genetic relationship with known sequences in each SFG rickettsiae species detected in the current study. Notably, the R. aeschlimannii sequences described in this study were closely related to those from abroad rather than from another part of China, indicating their different origin. However, the R. raoultii and Ca. R. jingxinensis sequences presented close relationship with variants from other parts of China. In sum, our data revealed SFG rickettsiae species in northern China, highlighting the need for surveillance of their infection in local humans.
斑点热群（SFG）立克次体是人类新发蜱传传染病的重要病原体，蜱在其维持和传播中发挥关键作用。在这项研究中，2017 年和 2018 年从中国北方的五个采样点收集了硬蜱。其中，从牲畜（绵羊和山羊）和植被中收集了长角血蜱、微小牛蜱和璃眼蜱，从绵羊、山羊和骆驼中收集了亚洲璃眼蜱，从绵羊和山羊中收集了边缘革蜱。通过扩增部分 rrs 和完整的 17-kDa 基因，在这些蜱中鉴定出 SFG 立克次体，总感染率为 52.9%。此外，还回收了近全长 rrs 和 gltA 以及部分 ompA 基因，以进一步分类 SFG 立克次体的种。系统发育分析显示，在亚洲璃眼蜱、边缘革蜱、长角血蜱和璃眼蜱中存在三种人类致病性种，包括两种培养种（拉乌尔立克次体和阿氏立克次体）和一种未培养种（候选立克次体 Jingxinensis）。此外，还获得了部分 groEL 基因，并构建了系统发育树，以更好地了解本研究中检测到的每种 SFG 立克次体的遗传关系。值得注意的是，本研究中描述的阿氏立克次体序列与国外的序列密切相关，而与中国其他地区的序列不相关，表明它们的起源不同。然而，拉乌尔立克次体和候选立克次体 Jingxinensis 序列与中国其他地区的变体密切相关。总之，我们的数据揭示了中国北方的 SFG 立克次体种，强调了对当地人群感染的监测。
