吉林延边地区蜱复合感染新塔拉塞维奇立克次体及SFTSV调查研究

  目的  为了解吉林省延边地区蜱类新塔拉塞维奇立克次体(candidatus rickettsia tarasevichiae，CRT)和复合感染新布尼亚病毒(sever fever thrombocytopenia syndrome virus，SFTSV)的感染情况。  方法  采集吉林省延边朝鲜族自治州(延边州)延吉、汪清、珲春、敦化、安图、和龙6个县游离蜱，进行形态学分类，通过巢式多聚核苷酸链式反应(nested polymerase chain reaction，nested PCR)和实时荧光定量多聚核苷酸链式反应(real-time quantitative polymerase chain reaction，RT-qPCR)方法检测蜱体内CRT和SFTSV。对其CRT进行目标DNA测序，分析同源性和系统进化关系。  结果  此研究共采集各种蜱类1 032只，分别为全沟硬蜱(ixodes persulcatus)(35.56%)、森林革蜱(dermacentor silvarum)(20.64%)、日本血蜱(haemaphysalis japonica)(20.45%)、长角血蜱(haemaphysalis longicornis)(10.47%)、嗜群血蜱(haemaphysalis concinna)(8.33%)以及其他种类(4.55%)。全沟硬蜱、长角血蜱、日本血蜱、森林革蜱检测出CRT，最低感染率(minimum infection rate per 100 ticks，MIR)为10.47%。嗜群血蜱、日本血蜱、全沟硬蜱、长角硬蜱、森林革蜱检测出SFTSV，最低感染率为2.52%。全沟硬蜱、日本血蜱、森林革蜱3种蜱存在CRT和SFTSV复合感染现象，复合感染MIR为1.26%。本研究CRT ompA和17kDa基因序列与中国河南信阳株(KX365196.1)序列同源性达100%。系统进化分析，延边地区蜱CRT ompA基因序列和该河南信阳株基因序列成为一簇，而17kDa基因则形成独立分支。  结论  本研究首次从吉林省延边地区游离蜱中检测出CRT，全沟硬蜱为主要媒介宿主。因此，可以明确该地区为新塔拉塞维奇立克次体病自然疫源地。同时发现，延边地区蜱类存在CRT与SFTSV复合感染的现象。因此，在该地区必须加强新塔拉塞维奇立克次体病和发热伴血小板减少综合征(sever fever thrombocytopenia syndrome，SFTS)疫情监测。

Investigation of free ticks carrying CRT and compound infection with SFTSV in Yanbian area of Jilin Province

  Objective  To understand the condition of tick carrying CRT(Candidatus rickettsia tarasevichiae) and compound infection with SFTSV(Sever fever thrombocytopenia syndrome virus) in Yanbian area of Jilin province.  Methods  Free ticks were collected from 6 counties including Yanji, Wangqing, Hunchun, Dunhua, Antu and Helong in the Korean Autonomous Prefecture of Jilin Province(Yanbian Prefecture) by using the flagging, and they were classified morphologically. The CRT and SFTSV in ticks were detected by Nest PCR(Nested polymerase chain reaction) and Real Time RT-PCR(Real-time Quantitative polymerase chain reaction) methods. Target DNA sequencing was performed for CRT positive products, and the homology of gene sequence and phylogenetic relationship were analyzed.  Results  A total of 1032 ticks were collected in this study, including ixodes persulcatus (35.56%) and dermacenter silvarum (20.64%). haemaphysalis japonica (20.45%), haemaphysalis longicornis (10.47%), haemaphysalis concinna (8.33%), others(4.55%). The CRT was detected from the Ixodes persulcatus, Haemaphysalis longicornis, Haemaphysalis japonica Dermacentor silvarum. The MIR(Minimum infection rate per 100 ticks) of CRT was 10.47%.The SFTSV was detected from the Haemaphysalis-concinna, Haemaphysalis-japonica, Ixodes-persulcatus, Haemaphysalis-longicornis, Dermacentor-silvarum. The MIR of SFTSV was 2.52%. Three species of ticks, including Ixodes persulcatus(2.45%), Haemaphysalis japonica(1.42%), and dermacentor silvarum(0.47%), had CRT and SFTSV compound infections, and the MIR of two pathogens compound infections was 1.26%. In this study, the gene sequence of CRT positive PCR products ompA and 17kDa with nucleotide sequence of Xinyang plant of HeNan XinYang strain (KX365196.1), had homology of 100%. Phylogenetic analysis showed that CRT ompA and the HeNan XinYang strain (KX365196.1) gene sequences formed a cluster in Yanbian, while the 17 kDa gene formed an independent branch.  Conclusions  For the first time, CRT was detected from free ticks in Yanbian area of Jilin Province, and it was found that Ixodes persulcatus may be the main medium of transmission of the pathogen. At the same time, it was found that CRT and SFTSV have compound infection in ticks of Yanbian area. Therefore, it can be clearly identified that Yanbian area in Jilin Province is the natural source of CRT, and there are two pathogenic compound infections in the local ticks.