Centers for Disease Control and Prevention, Rickettsial Zoonoses Branch, Atlanta GA 30029, USA.
J Med Entomol. 2012 May;49(3):783-6. doi: 10.1603/me11264.
The gophertortoise tick, Amblyomma tuberculatum (Marx), is distributed throughout the southeastern United States, and its immature life stages have been reported to occasionally bite humans. Here we report detection of a novel spotted fever group (SFG) Rickettsia in A. tuberculatum ticks collected in the southern United States. Among questing ticks collected in Georgia, 10 pools of larvae were identified as gophertortoise ticks, A. tuberculatum. Each of these samples was positive for SFG Rickettsiae. The restriction fragment-length polymorphism profiles were identical to each other, but distinct from those of other rickettsiae previously found in Amblyomma spp. ticks. Partial genetic characterization of the novel agent was achieved by sequencing the 17 kDa, gltA, ompB, ompA, rpoB, and sca4 genes. Analysis of a concatenated tree of four genes (gltA, ompB, ompA, and sca4) demonstrates close relatedness of the detected Rickettsia to several SFG Rickettsia spp. The identical rickettsial DNA was detected in 50 and 70% of adult A. tuberculatum ticks from Mississippi and Florida, respectively. The results indicate wide distribution of a novel Rickettsia, capability for transovarial transmission, and high prevalence in tested tick populations.
沟瘤龟蜱，即 Amblyomma tuberculatum（马克思），分布于美国东南部，其幼年期偶尔会叮咬人类。本研究报告了在美国南部采集的沟瘤龟蜱中发现了一种新型斑点热群（SFG）立克次体。在佐治亚州采集的游离蜱中，10 个幼虫样本被鉴定为沟瘤龟蜱，A. tuberculatum。这些样本均为 SFG 立克次体阳性。限制片段长度多态性图谱彼此相同，但与以前在 Amblyomma spp. 蜱中发现的其他立克次体不同。通过对 17 kDa、gltA、ompB、ompA、rpoB 和 sca4 基因进行测序，对新型病原体进行了部分遗传特征分析。对四个基因（gltA、ompB、ompA 和 sca4）的串联树分析表明，检测到的立克次体与几种 SFG 立克次体密切相关。在来自密西西比州和佛罗里达州的 50%和 70%的成年沟瘤龟蜱中分别检测到相同的立克次体 DNA。结果表明，新型立克次体分布广泛，具有经卵传递能力，且在检测的蜱种群中流行率较高。
