云南省泸西县小型哺乳动物携带斑疹伤寒立克次体调查

Investigation of Rickettsia typhi in small mammals in Luxi county,Yunnan province,China

目的了解云南省泸西县小型哺乳动物携带斑疹伤寒立克次体状况及其分子生物学特征,调查斑疹伤寒自然疫源地,为立克次体疾病的预防控制提供科学依据。方法用鼠笼和鼠夹法在云南省泸西县居民区及野外捕获小型哺乳动物,捕获的动物进行分类鉴定,活体取血并分离血清,采用间接免疫荧光试验检测血清中斑疹伤寒抗体。捕获动物均剖取脾脏并提取DNA,采用巢式PCR检测动物脾脏中斑疹伤寒立克次体groEL基因,阳性标本进行序列测定,通过美国国立生物技术信息中心网站对基因序列进行BLAST比对,构建系统进化树进行同源性及进化分析。结果2015年8月至2017年9月在泸西县共捕获小型哺乳动物193只,其中居民区64只,以黄胸鼠为优势鼠种;野外129只,以大绒鼠和中华姬鼠为优势鼠种。获得动物血清83份。动物脾脏巢式PCR扩增,居民区动物血清均为阴性,野外捕获动物中检测到2株groEL基因阳性标本(LX2和LX89),带菌鼠种为大绒鼠,带菌率为1.04%。对2份阳性标本测序,然后在基因BANK库中经BLAST比较分析,LX2和LX89相似性为100%,并与斑疹伤寒莫氏立克次体株(GenBank号:AF075440)相似性分别为100%和98%。系统进化树分析表明,LX2和LX89在同一分支,它们与斑疹伤寒莫氏立克次体AF075440株、AY191590株和AY191591株等遗传关系非常近。83份动物血清莫氏立克次体抗体阳性4份,阳性率为4.82%。结论云南省泸西县存在以大绒鼠为主要宿主的斑疹伤寒自然疫源地。

Objective To investigate the general status and molecular biological characteristics of Rickettsia typhi carried by small mammals in Luxi county,Yunnan province,China,as well as the national foci of typhus,and to provide a scientific basis for prevention and control of Rickettsia diseases.Methods Rat cages and rat traps were used to capture smalls in residential and wild areas in Luxi county.The captured animals were classified before their blood was collected from them alive for their sera.Indirect immunofluorescence assay was adopted to detect R.typhi antibodies in their sera.Spleens were cut off for DNA extraction and nested polymerase chain reaction(PCR)analysis to detect the groEL gene of R.typhi.Positive specimens were sequenced and analyzed by the Basic Local Alignment Search Tool(BLAST)provided by the National Center for Biotechnology Information(NCBI),and their phylogenetic trees were constructed for homology and evolution analysis.Results A total of 193 small mammals were captured in Luxi county,64 of which were in residential areas with Rattus tanezumi as the dominant species and 129 of which were in wild areas with Eothenomys miletus and Apodemus draco as the dominant species.Eighty-three sera samples were obtained.Nested PCR analysis of their spleens found all specimens in residential areas negative and 2 specimens(LX2,LX89)in wild areas positive for the groEL gene.The positive specimens were from E.miletus,yielding a carrying rate of 1.04%.The two positive specimens were sequenced and aligned by BLAST with known sequences in GenBank.LX2 and LX89 showed 100%identity,and they displayed 100% and 98% identity with R.mooseri(GenBank AF075440),respectively.Their phylogenetic trees suggested that they were in the same branch and closely related to AF075440,AY191590,and AY191591 strains of R.mooseri.Four of eighty-three rodents’sera were positive for R.mooseri antibodies with a positive rate of 4.82%.Conclusion There are natural foci of typhus mainly hosted by E.miletus in Luxi county,Yunnan province,China.