目的 研究湖北省随州市不同种属的蜱虫样本携带发热伴血小板减少综合征布尼亚病毒(severe fever with thrombocytopenia syndrome virus,SFTSV)情况,并探讨蜱虫与病例来源的病毒在分子进化水平上的亲缘关系.方法 于2016年、2017年连续2年在湖北省随州市采集蜱1158只,收集该地区具有发热和血小板减少症状的病例血清样本86份,检测病毒核酸.将阳性标本采用Vero细胞开展病毒分离、测定分离到毒株的全基因组序列,并开展蜱虫和病例来源SFTSV病毒株的同源性比较和系统发生研究.结果 湖北省随州市长角血蜱、中华硬蜱和微小扇头蜱为优势种(95.34％).根据蜱的种属和发育阶段合并样本,共得到832个合并样本,其中有4个检出SFTSV.该地区的总体最低感染率为0.35％.从长角血蜱中成功分离得到的1株SFTSV,命名为HB2016-P35.该毒株与湖北省已报道的16株病例来源病毒具有较高的同源性,特别是与来自于同一地区的人源毒株HB 2017-49具有高度的同源性(基因组相似度99.9％).此外,研究结果表明湖北省SFTSV病毒存在至少5个基因型,涵盖了几乎所有已报道的SFTSV基因型.结论 湖北省随州市蜱携带及传播SFTSV整体上处于较低水平.新分离自蜱虫的SFTSV毒株与周边病例携带病毒具有相似的基因型特征和较高的序列同源性.本研究结果提示蜱-人传播最有可能是人类感染SFTSV的途径,需持续在发热伴血小板减少综合征(severe fever with thrombocytopenia syndrome,SFTS)流行地区开展长期蜱虫携带 SFTSV 监测.
Prevalence of severe fever with thrombocytopenia syndrome virus in ticks and molecular phylogenetic study of viruses in an epidemic area of Suizhou,Hubei Province
Objective To study severe fever with thrombocytopenia syndrome virus(SFTSV)in tick samples from different species and genera in Suizhou City,Hubei Province,China,and to explore the phylogenetic relationship between ticks and patients sources of viruses at the molecular evolutionary level.Methods In 2016 and 2017,over a continuous two-year period,1 158 ticks were collected from Suizhou,Hubei,and their species and genera were identified.Meanwhile,86 serum samples were collected to detect SFTSV RNA by real-time quantitative reverse transcription-PCR.All viral RNA-positive supernatants of tick homogenates were inoculated into Vero cells for viral isolation,and full genome sequencing of isolated strains was conducted.Phylogenetic tree research on SFTSV strains from ticks and cases was performed using the bootstrapped maximum-likelihood(1 000 iterations)method with Molecular Evolutionary Genetics Analysis(MEGA)software,ver.11.0 to provide confidence estimates.Results Haemaphysalis longicornis,Ixodes sinensis,and Rhipicephalus microplus were the dominant species(95.34％)in Suizhou City,Hubei Province,China.Tick samples were pooled according to their species and developmental stage,yielding 832 pools,of which 4 were positive for SFTSV by qRT-PCR.The overall minimum infection rate(MIR)in the region was 0.35％.One SFTSV strain named HB 2016-P35,was successfully isolated from Haemaphysalis longicornis and demonstrated high homology to 16 previously reported patient-derived viruses in Hubei Province,especially to the human strain HB 2017-49 from the same region,with a genome similarity of 99.9％.In addition,the molecular phylogenetic analysis revealed five distinct SFTSV genotypes in Hubei,covering almost all currently known SFTSV genotypes.Conclusions Some areas of Suizhou City,Hubei Province,demonstrate a relatively low level of SFTSV carrying and transmission by ticks.The new SFTSV strain isolated from ticks exhibits similar genotype characteristics and high sequence homology with viruses carried by cases in surrounding cases.The study suggests that tick-to-human transmission is most likely the pathway for human infection with SFTSV,highlighting the need for continual and long-term monitoring of tick carriage of SFTSV in endemic areas.
Fever with thrombocytopenia syndromesevere fever with thrombocytopenia syndrome virustickvirus carrying ratephylogenetic analysisHubei Province
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