Department of Laboratory Medicine, University of California, San Francisco, CA, 94143, USA.
Department of Biology, San Francisco State University, San Francisco, CA, 94132, USA.
Sci Rep. 2017 Sep 25;7(1):12234. doi: 10.1038/s41598-017-12047-6.
An increasing number of emerging tick-borne diseases has been reported in the United States since the 1970s. Using metagenomic next generation sequencing, we detected nucleic acid sequences from 2 novel viruses in the family Bunyaviridae and an emerging human rickettsial pathogen, Rickettsia philipii, in a population of the Pacific Coast tick, Dermacentor occidentalis in Mendocino County sampled annually from 2011 to 2014. A total of 250 adults of this human-biting, generalist tick were collected from contiguous chaparral and grassland habitats, and RNA from each individually extracted tick was deep sequenced to an average depth of 7.3 million reads. We detected a Francisella endosymbiont in 174 ticks (70%), and Rickettsia spp. in 19 ticks (8%); Rickettsia-infected ticks contained R. rhipicephali (16 of 250, 6.4%) or R. philipii (3 of 250,1.2%), the agent of eschar-associated febrile illness in humans. The genomes of 2 novel bunyaviruses (>99% complete) in the genera Nairovirus and Phlebovirus were also identified and found to be present in 20-91% of ticks, depending on the year of collection. The high prevalence of these bunyaviruses in sampled Dermacentor ticks suggests that they may be viral endosymbionts, although further studies are needed to determine whether they are infectious for vertebrate hosts, especially humans, and their potential role in tick ecology.
自 20 世纪 70 年代以来，美国报告的新兴蜱传疾病数量不断增加。我们使用宏基因组下一代测序技术，在加利福尼亚州门多西诺县每年采集的太平洋海岸革蜱（Dermacentor occidentalis）种群中，检测到了两种布尼亚病毒科的新病毒和一种新兴的人类立克次体病原体，即菲利普立克次体的核酸序列。从 2011 年到 2014 年，共采集了 250 只这种叮咬人类的多宿主普通蜱。从相邻的灌木和草原栖息地采集了总共 250 只成年蜱，并从每只单独提取的蜱中提取 RNA，进行深度测序，平均深度为 730 万读。我们在 174 只蜱（70%）中检测到弗朗西斯菌共生体，在 19 只蜱（8%）中检测到立克次体；感染立克次体的蜱含有蜱传斑点热立克次体（250 只中的 16 只，6.4%）或菲利普氏立克次体（250 只中的 3 只，1.2%），这是人类埃斯库拉热相关发热病的病原体。两种新的布尼亚病毒（>99%完整）的基因组也被鉴定出来，属于纳罗病毒属和菲莱病毒属，其存在取决于采集年份，在 20-91%的蜱中存在。在所采样的革蜱中，这些布尼亚病毒的高流行率表明它们可能是病毒共生体，尽管需要进一步研究来确定它们是否对脊椎动物宿主，特别是人类具有传染性，以及它们在蜱生态学中的潜在作用。
