Stromdahl Ellen Y, Nadolny Robyn M, Hickling Graham J, Hamer Sarah A, Ogden Nicholas H, Casal Cory, Heck Garrett A, Gibbons Jennifer A, Cremeans Taylor F, Pilgard Mark A
Army Public Health Center, Aberdeen Proving Ground, MD.
Center for Wildlife Health, The University of Tennessee Institute of Agriculture, Knoxville, TN.
J Med Entomol. 2018 May 4;55(3):501-514. doi: 10.1093/jme/tjx250.
In the early 1980s, Ixodes spp. ticks were implicated as the key North American vectors of Borrelia burgdorferi (Johnson, Schmid, Hyde, Steigerwalt and Brenner) (Spirocheatales: Spirochaetaceae), the etiological agent of Lyme disease. Concurrently, other human-biting tick species were investigated as potential B. burgdorferi vectors. Rashes thought to be erythema migrans were observed in patients bitten by Amblyomma americanum (L.) (Acari: Ixodidae) ticks, and spirochetes were visualized in a small percentage of A. americanum using fluorescent antibody staining methods, sparking interest in this species as a candidate vector of B. burgdorferi. Using molecular methods, the spirochetes were subsequently described as Borrelia lonestari sp. nov. (Spirocheatales: Spirochaetaceae), a transovarially transmitted relapsing fever Borrelia of uncertain clinical significance. In total, 54 surveys from more than 35 research groups, involving more than 52,000 ticks, have revealed a low prevalence of B. lonestari, and scarce B. burgdorferi, in A. americanum. In Lyme disease-endemic areas, A. americanum commonly feeds on B. burgdorferi-infected hosts; the extremely low prevalence of B. burgdorferi in this tick results from a saliva barrier to acquiring infection from infected hosts. At least nine transmission experiments involving B. burgdorferi in A. americanum have failed to demonstrate vector competency. Advancements in molecular analysis strongly suggest that initial reports of B. burgdorferi in A. americanum across many states were misidentified B. lonestari, or DNA contamination, yet the early reports continue to be cited without regard to the later clarifying studies. In this article, the surveillance and vector competency studies of B. burgdorferi in A. americanum are reviewed, and we conclude that A. americanum is not a vector of B. burgdorferi.
20世纪80年代初，硬蜱属蜱虫被认为是北美传播伯氏疏螺旋体（约翰逊、施密德、海德、施泰格瓦尔特和布伦纳）（螺旋体目：螺旋体科）的主要媒介，伯氏疏螺旋体是莱姆病的病原体。与此同时，其他叮咬人类的蜱虫种类也作为潜在的伯氏疏螺旋体媒介受到研究。在被美洲钝眼蜱（L.）（蜱螨亚纲：硬蜱科）叮咬的患者身上观察到被认为是游走性红斑的皮疹，并且使用荧光抗体染色方法在一小部分美洲钝眼蜱中观察到了螺旋体，这引发了人们对该物种作为伯氏疏螺旋体候选媒介的兴趣。随后，利用分子方法将这些螺旋体描述为新种孤独疏螺旋体（螺旋体目：螺旋体科），这是一种经卵传播的回归热疏螺旋体，其临床意义尚不确定。来自35多个研究小组的总共54项调查，涉及超过52000只蜱虫，结果显示美洲钝眼蜱中孤独疏螺旋体的感染率较低，伯氏疏螺旋体也很稀少。在莱姆病流行地区，美洲钝眼蜱通常吸食感染伯氏疏螺旋体的宿主血液；这种蜱中伯氏疏螺旋体的感染率极低是由于唾液屏障阻止其从感染宿主获取感染。至少九项涉及美洲钝眼蜱传播伯氏疏螺旋体的实验未能证明其具备媒介能力。分子分析的进展有力地表明，许多州关于美洲钝眼蜱中存在伯氏疏螺旋体的初步报告被误鉴定为孤独疏螺旋体，或者是DNA污染，但早期报告仍被引用，而未考虑后来的澄清研究。在本文中，我们对美洲钝眼蜱中伯氏疏螺旋体的监测和媒介能力研究进行了综述，并得出结论：美洲钝眼蜱不是伯氏疏螺旋体的媒介。
