长角血蜱携带发热伴血小板减少综合征病毒调查及基因特征分析

Survey and genetic analysis of severe fever with thrombocytopenia syndrome virus from Haemaphysalis longicornis

目的探讨长角血蜱携带发热伴血小板减少综合征病毒（SFTSV）情况及其基因特征,分析长角血蜱在发热伴血小板减少综合征（SFTS）传播中的作用。方法在SFTS严重流行区河南省信阳市采集长角血蜱,采用实时RTPCR方法检测蜱中SFTSV核酸,阳性蜱进行SFTSV全基因组序列测定,并与当地病人血液中的SFTSV序列及GenBank中公布的SFTSV全基因组序列进行比较。结果共检测285只长角血蜱,SFTSV携带率为20.4%（58/285）。其中,游离蜱携带率31.9%（46/144）,寄生蜱携带率8.5%（12/141）,差异有统计学意义（χ2=24.136,P〈0.01）。基于SFTSV的L、M和S片段构建的系统发育树,信阳地区长角血蜱的SFTSV序列与来自当地病人的SFTSV序列聚在同一分支,序列同源性分别为99.5%～99.7%,99.4%～99.5%和99.4%～99.5%。结论信阳地区SFTS高发病率与当地长角血蜱SFTSV高携带率有关,长角血蜱可能是SFTSV的传播媒介。

Objective To examine severe fever with thrombocytopenia syndrome virus（SFTSV）infection in Haemaphysalis longicornis and its genetic characteristics and to investigate the role of H.longicornis in transmitting SFTSV. Methods Ticks were collected in the City of Xinyang,Henan Province from April to July when ticks were active.The City of Xinyang was chosen since severe fever with thrombocytopenia syndrome（SFTS）is highly endemic.SFTSV in ticks was detected using real-time RT-PCR.The complete genome of the SFTSV was sequenced from ticks with the SFTSV,and the genome was compared to sequences of the SFTSV in the blood of local patients and in GenBank. Results A total of 285 ticks were collected,20.4%of which（58/285）were positive for the SFTSV;31.9% of free ticks（46/144）were positive for the SFTSV while 8.5%of ticks on hosts（12/141）were positive.The difference in positivity for the SFTSV was significant（Chi-square test,χ2=24.136,P〈0.01）.A phylogenetic tree based on the L,M,and S segments showed that sequences were clustered into five branches and the SFTSV detected in H.longicornis ticks was clustered in the same clade with the SFTSV isolated from patients.Sequence identity for the L segment was 99.5%-99.7%,that for the M segment was 99.4%-99.5%,and that for the S segment was 99.4%-99.5%. Conclusion The high incidence of SFTS in the City of Xinyang might be due to the high rate of SFTSV infection in H.longicornis.H.longicornis is probably the transmission vector for the SFTSV.