Billings A N, Yu X J, Teel P D, Walker D H
Department of Pathology, University of Texas Medical Branch, Galveston 77555-0609, USA.
J Med Entomol. 1998 Jul;35(4):474-8. doi: 10.1093/jmedent/35.4.474.
Thai tick typhus rickettsia (strain TT-118), a spotted fever group rickettsia of indeterminant pathogenicity, was isolated from a mixed pool of larval Ixodes and Rhipicephalus ticks collected from Thailand in 1962. Here we report the surprising finding of a spotted fever group rickettsia with closest sequence homology to the Thai tick typhus rickettsia in Amblyomma cajennense (F.) ticks from south Texas. Sequence analysis was performed on segments of 3 genes that differentiate rickettsial species; all 3 genes sequenced, the 17-kDa, glta, and rompA, when compared with those of other rickettsiae, showed the highest degree of similarity to the Thai tick typhus rickettsia with 99.5, 99.5, and 100% homology, respectively. This is the 1st finding of a rickettsial species in A. cajennense ticks in Texas and the United States. If this rickettsia is pathogenic, exposure to infected A. cajennense ticks may pose a previously unrecognized health risk to people who have been fed upon by these ticks.
泰国蜱传斑疹伤寒立克次体（菌株TT - 118）是一种致病性不明的斑点热群立克次体，于1962年从泰国采集的混合幼蜱（硬蜱属和璃眼蜱属）中分离得到。在此，我们报告了一个惊人的发现：在得克萨斯州南部的卡延花蜱（A. cajennense (F.)）中发现了一种与泰国蜱传斑疹伤寒立克次体序列同源性最高的斑点热群立克次体。对区分立克次体物种的3个基因片段进行了序列分析；所测序的全部3个基因，即17-kDa、glta和rompA，与其他立克次体相比，与泰国蜱传斑疹伤寒立克次体的相似性最高，同源性分别为99.5%、99.5%和100%。这是在美国得克萨斯州的卡延花蜱中首次发现立克次体物种。如果这种立克次体具有致病性，接触受感染的卡延花蜱可能会给被这些蜱叮咬过的人带来前所未有的健康风险。
