School of Public Health, Cheeloo College of Medicine, Shandong University, Jinan, Shandong, P. R. China.
State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, P. R. China.
J Med Entomol. 2021 May 15;58(3):1363-1369. doi: 10.1093/jme/tjaa294.
Spotted fever group rickettsiae, mainly maintained and transmitted by ticks, are important etiological agents of (re)emerging zoonotic diseases worldwide. It is of great significance to investigate spotted fever group rickettsiae in ticks in different areas for the prevention and control of rickettsioses. In this study, a total of 305 ticks were collected from wild and domestic animals in Chongqing, Guizhou, Yunnan, and Guangxi provinces of southwestern China during 2017-2019 and examined for the presence of spotted fever group rickettsiae by PCR with primers targeting the partial gltA, ompA, rrs, and htrA genes. Results showed that two spotted fever group rickettsiae species, including the pathogenic Candidatus Rickettsia jingxinensis (Rickettsiales: Rickettsiaceae) and a potential novel species Rickettsia sp. sw (Rickettsiales: Rickettsiaceae), were identified. The Ca. R. jingxinensis sequences were recovered from Rhipicephalus microplus (Ixodida: Ixodidae) and Haemaphysalis longicornis (Ixodida: Ixodidae) ticks and phylogenetically clustered with previous Ca. R. jingxinensis, Ca. R. longicornii (Rickettsiales: Rickettsiaceae), and Rickettsia sp. XY118 (Rickettsiales: Rickettsiaceae) strains. Rickettsia sp. sw was detected in Amblyomma geoemydae (Ixodida: Ixodidae) and Rh. microplus. Interestingly, as far as we know, this was the first report of Rickettsia (Rickettsiales: Rickettsiaceae) in A. geoemydae. Phylogenetic analyses indicated that this potential novel species was closely related to R. aeschlimannii (Rickettsiales: Rickettsiaceae) with gltA and ompA genes and grouped in a cluster composed of R. montanensis (Rickettsiales: Rickettsiaceae), R. raoultii (Rickettsiales: Rickettsiaceae), R. aeschlimannii, R. massiliae (Rickettsiales: Rickettsiaceae), and R. rhipicephali (Rickettsiales: Rickettsiaceae) with htrA, while formed a separate clade with rrs. The pathogenicity of Rickettsia sp. sw should be further confirmed. These results expand the knowledge of the geographical distribution and vector distribution of spotted fever group rickettsiae in China and are useful for assessing the potential public health risk.
斑点热群立克次体主要由蜱类维持和传播，是全球新出现的人畜共患传染病的重要病原体。调查不同地区蜱类中的斑点热群立克次体对于立克次体病的预防和控制具有重要意义。本研究于 2017-2019 年在我国西南地区的重庆、贵州、云南和广西等省的野生动物和家畜中采集了 305 只蜱，采用针对 gltA、ompA、rrs 和 htrA 基因部分序列的 PCR 方法检测斑点热群立克次体。结果显示，鉴定出两种斑点热群立克次体，包括致病性候选立克次体京新立克次体（立克次体目：立克次体科）和一种潜在的新种立克次体 sw（立克次体目：立克次体科）。候选立克次体京新立克次体序列从微小牛蜱（硬蜱科）和长角血蜱（硬蜱科）中获得，与以前的候选立克次体京新立克次体、长角血蜱立克次体（立克次体目：立克次体科）和立克次体 XY118（立克次体目：立克次体科）菌株聚为一簇。立克次体 sw 在中华鳖龟（硬蜱科）和微小牛蜱中被检测到。有趣的是，据我们所知，这是首次在中华鳖龟中报告立克次体（立克次体目：立克次体科）。系统发育分析表明，这种潜在的新种与 gltA 和 ompA 基因的拉氏立克次体密切相关，与蒙氏立克次体（立克次体目：立克次体科）、拉乌尔立克次体（立克次体目：立克次体科）、拉氏立克次体、马赛立克次体（立克次体目：立克次体科）和硬蜱立克次体（立克次体目：立克次体科）形成一个聚类，与 htrA 形成一个聚类，而与 rrs 形成一个单独的分支。立克次体 sw 的致病性有待进一步确认。这些结果扩展了中国斑点热群立克次体的地理分布和媒介分布知识，有助于评估潜在的公共卫生风险。
