Division of Infectious Diseases and Duke Global Health Institute, Duke University, Durham, North Carolina, United States of America.
Miller School of Medicine, University of Miami, Miami, Florida, United States of America.
PLoS Negl Trop Dis. 2018 Aug 27;12(8):e0006696. doi: 10.1371/journal.pntd.0006696. eCollection 2018 Aug.
Transstadial transmission of tick-borne rickettsiae has been well documented. Few studies, however, have evaluated the role of transovarial transmission of tick-borne rickettsiae, particularly in nature within the host-vector ecosystem. This cross-sectional study aimed to understand the role of transovarial transmission of tick-borne rickettsiae among feeding ticks at different life stages. Tick eggs laid by engorged wild-caught adult female ticks were pooled and tested for Rickettsia spp. and Anaplasma/Ehrlichia spp. using molecular techniques, while adult fed ticks were tested individually. Additionally, larval and nymphal ticks were collected in the wild from small mammals, pooled and tested for Rickettsia spp. and Anaplasma/Ehrlichia spp. There were 38 fed adult and 618 larvae/nymphs (60 pools total) Dermacentor spp. ticks collected from livestock and rodents. All individual adult ticks and tick pools were positive for Rickettsia spp. While none of the larvae/nymphs were positive for Anaplasma/Ehrlichia spp., two adult fed ticks were positive. Rickettsia spp. DNA was detected in 91% (30/33) of the pooled eggs tested, and one pool of eggs tested positive for Anaplasma/Ehrlichia spp. Sequencing data revealed Rickettsia spp. shared ≥99% identity with R. raoultii ompA. Anaplasma/Ehrlichia spp. shared ≥89% identity with A. ovis 16S ribosomal RNA. This study identified potential transovarial transmission of Rickettsia spp. and Anaplasma spp. among D. nuttalli ticks. Additional studies are needed to further assess the proportion of transovarial transmission occurring in nature to better understand the burden and disease ecology of tick-borne rickettsiae in Mongolia.
蜱传立克次体的经卵传递已得到充分证实。然而，很少有研究评估蜱传立克次体的经卵传递作用，特别是在宿主-媒介生态系统中的自然状态下。本横断面研究旨在了解不同生命阶段的吸血蜱经卵传递蜱传立克次体的作用。用分子技术检测从饱血野生捕获的成年雌性蜱所产的蜱卵中是否存在立克次体属和无形体/埃立克体属，同时单独检测成年吸血蜱。此外，从小型哺乳动物中野外采集幼虫和若虫蜱，混合并检测立克次体属和无形体/埃立克体属。从家畜和啮齿动物中采集了 38 只成年吸血蜱和 618 只幼虫/若虫（共 60 个混合样本）。所有单独的成年蜱和蜱混合样本均为立克次体属阳性。虽然幼虫/若虫中没有检测到无形体/埃立克体属阳性，但有 2 只成年吸血蜱阳性。检测了 33 个混合蜱卵样本中的 30 个，其中 91%（30/33）检测到立克次体属 DNA，一个蜱卵混合样本检测到无形体/埃立克体属阳性。测序数据显示，立克次体属与拉乌尔氏立克次体 ompA 具有≥99%的同源性。无形体/埃立克体属与绵羊无形体 16S 核糖体 RNA 具有≥89%的同源性。本研究鉴定了在 D. nuttalli 蜱中存在立克次体属和无形体属的潜在经卵传递。需要进一步的研究来评估自然状态下经卵传递的比例，以更好地了解蒙古蜱传立克次体的负担和疾病生态学。
