National Center for Disease Control and Public Health, Tbilisi, Georgia.
Naval Medical Research Center, Silver Spring, MD, USA.
Ticks Tick Borne Dis. 2020 Sep;11(5):101470. doi: 10.1016/j.ttbdis.2020.101470. Epub 2020 May 23.
Rickettsial pathogens cause diseases that vary in severity and clinical presentation. Rickettsia species transmitted by ticks are mostly classified within the spotted fever group of rickettsiae (SFGR) and are often associated with febrile diseases. Preliminary studies have detected three human-pathogenic SFGR from ticks in Georgia: Rickettsia aeschlimannii, Rickettsia raoultii, and Rickettsia slovaca. To more broadly assess the presence of tick-borne rickettsiae from Georgia we examined 1594 ticks, representing 18 species from five genera (Ixodes, Hyalomma, Haemaphysalis, Dermacentor, and Rhipicephalus), collected from eight regions of Georgia. A total of 498 tick DNA samples extracted from single ticks or pooled ticks were assessed by molecular methods. Genus-specific Rick17b and species-specific qPCR assays were used to identify six rickettsiae: R. aeschlimannii, R. raoultii, R. slovaca, Rickettsia conorii subsp. conorii, Rickettsia massiliae, and Rickettsia monacensis. Tick samples that were positive for Rickettsia, but not identified by the species-specific assays, were further evaluated by multi-locus sequence typing (MLST) using sequences of four protein-coding genes (gltA, ompA,ompB, sca4). Three additional Rickettsia species were identified by MLST: Candidatus Rickettsia barbariae, Rickettsia helvetica, and Rickettsia hoogstraalii. Overall, nine species of Rickettsia (six human pathogens and three species with unknown pathogenicity) were detected from 12 tick species of five different genera. A distribution map for the tick-borne rickettsiae revealed six newly identified endemic regions in Georgia.
立克次体病原体引起的疾病在严重程度和临床表现上有所不同。通过蜱传播的立克次体物种主要分类为斑点热群立克次体（SFGR），通常与发热疾病有关。初步研究从格鲁吉亚的蜱中检测到三种人类致病性 SFGR：拉氏立克次体、瑞氏立克次体和斯洛伐克立克次体。为了更广泛地评估来自格鲁吉亚的蜱传立克次体的存在，我们检查了 1594 只蜱，代表来自五个属（硬蜱属、璃眼蜱属、血蜱属、革蜱属和扇头蜱属）的 18 个种，这些蜱来自格鲁吉亚的八个地区。从单个蜱或多个蜱中提取的总共 498 个蜱 DNA 样本通过分子方法进行评估。使用属特异性 Rick17b 和种特异性 qPCR 检测来鉴定六种立克次体：拉氏立克次体、瑞氏立克次体、斯洛伐克立克次体、康氏立克次体、马赛立克次体和单核细胞埃立克体。通过种特异性检测未鉴定出但对立克次体呈阳性的蜱样本，进一步通过使用四个蛋白编码基因（gltA、ompA、ompB、sca4）的多位点序列分型（MLST）进行评估。通过 MLST 还鉴定了另外三种立克次体：巴尔的摩立克次体、瑞士立克次体和霍格斯特拉立克次体。总体而言，从五个不同属的 12 种蜱中检测到了九种立克次体（六种人类病原体和三种致病性未知的物种）。蜱传立克次体的分布图显示了格鲁吉亚的六个新确定的地方性流行区域。
