陕西省蜱源性立克次氏体目细菌的遗传多样性及病原体分离

Arthropod has been an important source of pathogens infecting humans and animals. Ticks can harbor a large number of viruses and bacteria (including Rickettsiales) and act as the vectors and hosts of humans and animals etiologic agents. Rickettsiales belong to the alpha Proteobacteria and comprises of a group of obligate intracellular bacterium. Most of them are transmitted by ticks through blood-feeding. Many Rickeckttsiales bacterium are best known as agents of human beings and veterinary disease, causing severe diseases including death. Diseases caused by tick-borne Rickettsiales are natural-focal diseases, therefore, investigating the epidemic situation of Rickettsiales bacterium in the natural foci is important for disease prevention and control. Our project aims to perform the molecular epidemiological investigation of Rickettsiales ticks in Shaanxi Province. Here, using the molecular biological methods, the infection of Rickettsiales bacterium in ticks and domestic animals will be inferred. In addition, this study will also demonstrate the genetic characters, diversity and geographic distribution of Rickettsiales, and their association with hosts. Besides, identification and isolation of novel Rickettsiales will also be performed. The phylogenetic relationship between strains in this study and other known strains in and outside China will be estimated by using Maximum likelihood and Bayesian methods. The data from this project will be helpful to prevent the disease caused by Rickettsiales in Shaanxi Province.

许多感染人与动物的病原体均来自于节肢动物。蜱可以携带大量的病毒与细菌(包括立克次氏体目细菌)，是人与动物多种病原体的重要传播媒介与宿主。立克次氏体目细菌属于α变形菌门，是一类严格的胞内寄生微生物，其传播媒介主要为蜱。立克次氏体目中的多种细菌是人与动物疾病的病原体，可引起严重的疾病，甚至造成死亡。蜱传立克次氏体目细菌引起的疾病属于自然疫源性疾病，因此，查清楚其在自然疫源地中的流行情况对于疾病的防控非常重要。本项目拟对陕西省的蜱及其携带的立克次氏体目细菌进行调查。采用分子生物学方法，研究立克次氏体目细菌在蜱与家养动物中的流行状况，揭示其遗传特征及多样性、地理分布、以及与宿主间的关系。发现新立克次氏体目细菌，并用细胞培养的方法分离。采用最大似然法与贝叶斯系统发生分析方法研究该地区立克次氏体目细菌与国内外已知病原体间的进化关系。本项目将为陕西省立克次体病的预防与控制提供科学依据。

蜱传立克次氏体目细菌中的多个物种是人与动物疾病的病原体，可引起严重的疾病，甚至造成死亡。蜱传立克次氏体目细菌引起的疾病属于自然疫源性疾病，因此，查清楚其在自然疫源地中的流行情况对于疾病的防控非常重要。本项目拟对陕西省的蜱源性立克次氏体目细菌进行调查。研究结果显示，西安的病媒蜱种主要为微小扇头蜱与长角血蜱，宝鸡为长角血蜱；陕南地区的安康主要为微小扇头蜱，汉中主要为长角血蜱；陕北的榆林地区主要为草原革蜱。西安主要流行山羊无形体、羊无形体、牛无形体与Candidatus Rickettsia jingxinensis；宝鸡流行牛无形体、山羊无形体与Candidatus R. jingxinensis；汉中流行牛无形体与Candidatus R. jingxinensis；安康流行牛无形体、山羊无形体、边缘无形体与扁平无形体类无形体；榆林流行羊无形体与西伯利亚立克次体。此外，汉中流行着两种未分类的埃立克体，安康流行一种未分类的埃立克体。同时，我们在西安鉴定出了两种无形体属的新种：周至无形体与东大无形体。此外，结合西安流行的牛无形体多样性，本研究还着重对牛无形体的进化进行了分析。基于groEL或gltA基因序列的分析显示，中国以外的牛无形体呈宿主源聚类。此外，groEL和gltA基因的系统发生分析表明，近年来频繁的长距离传播和在长时间尺度上的局部适应在中国牛无形体的分布和进化中发挥了重要作用。本项目将为陕西省立克次体病的预防与控制提供科学依据。