Ferrari F A G, Goddard J, Paddock C D, Varela-Stokes A S
Department of Basic Sciences, College of Veterinary Medicine, Mississippi State University, 240 Wise Center Drive, Mississippi State, MS 39762, USA.
Department of Biochemistry, Molecular Biology, Entomology & Plant Pathology, 100 Old Hwy 12, Mississippi State University, Mississippi State, MS 39762, USA.
J Med Entomol. 2014 Nov 1;51(6):1317-21. doi: 10.1603/ME14132.
Amblyomma maculatum Koch, 1844 (also known as the Gulf Coast tick) is found in parts of the Americas, including the central and southern United States. Its primary importance is as the vector of Rickettsia parkeri, a spotted fever group rickettsia that causes an illness similar to, but milder than, Rocky Mountain spotted fever. A second spotted fever group rickettsia, "Candidatus Rickettsia andeanae," was detected in Gulf Coast ticks approximately 10 yr ago. However, the significance of this organism, including pathogenicity, has not yet been well-characterized. Here, we use transmission electron microscopy to describe bacteria within the tissues of A. maculatum ticks that were positive by polymerase chain reaction assay for "Ca. R. andeanae." In ultrathin sections of unfed A. maculatum adult females, we found evidence of bacteria with morphological features consistent with spotted fever group rickettsiae, including small size (≈0.3 by 0.9 μm), a halo zone (electron-lucent layer around the bacterium), and a trilaminar cell wall. In female ticks, bacteria were present in granular salivary glands and ducts, foregut, Malpighian tubules, nerve trunks, and reproductive tissue. These findings demonstrate evidence of "Ca. R. andeanae" in situ and contribute to our understanding of this novel rickettsia in A. maculatum.
美洲钝眼蜱（Amblyomma maculatum Koch，1844年）（也被称为墨西哥湾沿岸蜱）分布于美洲部分地区，包括美国中部和南部。它的主要重要性在于作为帕克立克次体（Rickettsia parkeri）的传播媒介，帕克立克次体是斑点热群立克次体，可引起一种与落基山斑点热相似但症状较轻的疾病。大约10年前，在墨西哥湾沿岸蜱中检测到了第二种斑点热群立克次体，即“安德纳立克次体（Candidatus Rickettsia andeanae）”。然而，这种微生物的重要性，包括致病性，尚未得到充分描述。在此，我们使用透射电子显微镜来描述通过聚合酶链反应检测呈“安德纳立克次体”阳性的美洲钝眼蜱组织内的细菌。在未进食的美洲钝眼蜱成年雌性的超薄切片中，我们发现了具有与斑点热群立克次体一致形态特征的细菌证据，包括小尺寸（约0.3×0.9μm）、晕圈区域（细菌周围的电子透明层）和三层细胞壁。在雌性蜱中，细菌存在于颗粒状唾液腺和导管、前肠、马氏管、神经干和生殖组织中。这些发现证明了“安德纳立克次体”的原位证据，并有助于我们对美洲钝眼蜱中这种新型立克次体的理解。
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