浙江中部地区啮齿动物恙虫病东方体分子流行病学调查

Molecular epidemioiogical investigation of Orientia tsutsugamushi among rodent animals in central Zhejiang

目的 了解浙江中部啮齿动物中恙虫病东方体的自然感染状况及其分子生物学特性.方法 2015年3—11月在义乌地区3个自然村的野外和居住地捕获啮齿动物687只;取肝脾行PCR检测恙虫病东方体groEL基因并测序;采用MEGA7.0软件最大似然法进行系统发生聚类分析,采用RelTime方法生成的时间树比较义乌菌株序列与祖先分歧的发生时间.结果 687只啮齿动物检出恙虫病东方体感染26只,总体感染率为3.78％,其中3—7月捕获的352只groEL基因均阴性,8—11月份捕获的335只中有26只阳性.9—10月份感染率较高,分别为11.32％（6/53）和10.00％（9/90）.感染率总体呈上升趋势（x2趋势=25.85,P〈0.01）.4个优势鼠种黑线姬鼠、黑腹绒鼠、针毛鼠和臭鼩鼱存在恙虫病东方体感染,黑线姬鼠感染率最高为8.67％（13/150）.26只阳性动物中,25只捕获于野外,25只捕获于大陈镇.系统发生分析表明义乌地区啮齿动物中恙虫病东方体groEL基因变异较大,可能存在Kato、Boryong、O3和其他尚不能确定的基因型,时间树分析显示义乌不同菌株出现的时间不一致.结论 浙江中部啮齿动物中存在恙虫病东方体感染,其groEL基因分布在不同支系.

Objective To understand the natural infection of Orientia tsutsugamushi among rodent animals in central Zhejiang and its molecular biological characteristics. Methods Low hilly regions and residential regions of three survey sites in Yiwu were selected and 687 rodent animals were captured from March to November 2015. groEL gene of O. tsutsugamushi in the livers and spleens were detected and sequenced by PCR. The evolutionary analyse was conducted by Maximum Likelihood method of MEGA7.0 software. The time tree was generated by Reltime method to estimate divergence times for all branching points in the topology. Results Of 687 rodent animals captured, 26 were positive for O. tsutsugamushi and the infection rate was 3.78%. There were 352 rodent animals captured from March to July and groEL were negative. While there were 355 rodent animals captured from August to November and 26 were groEL-positive. The infection rates for O. tsutsugamushi were high in September and October, accounting for 11.32% （6/53） and 10.00% （9/90）, respectively. The trend of infection rate was increasing （x2trend =25.85,P 〈0.01）. O. tsutsugamushi infection existed in four dominant mice species including Eothenomys melanogaster, A. agrarius, Niviventer fulvescens and Suncus murinus. Of those, the infection rate was the highest in A. agrarius of 8.67% （13/150）. Of 26 positive rodent animals, 25 were captured in the field and 25 were captured in Dachen town . The alignment and phylogenetic analysis showed that the groEL gene sequences were different obviously . O. tsutsugamushi genotypes including Kato, Boryong , O3 and other unknown genotypes were likely to exist among rodents in Yiwu region . The time tree analysis showed that emerging times of the different strains in Yiwu were inconsistent. Conclusions O. tsutsugamushi infection exists in rodents in central Zhejiang. The groEL gene distributes in different strains.