血清学和分子生物学证实云南省勐海县存在恙虫病流行

Serological and molecular biological confirmation of transmission of scrub typhus in Menghai,Yunnan

目的了解云南省勐海县恙虫病流行状况。方法 2011年6 9月,在勐海县采集恙虫病临床诊断和疑似病例急性期和恢复期血液标本,用巢式聚合酶链反应（nPCR）对患者凝血块进行恙虫病东方体（Ot）热休克蛋白（groEL）基因扩增和测序分析。用间接免疫荧光试验（IFA）检测患者血清中Ot-IgG抗体。结果 36例急性期患者凝血块标本经聚合酶链反应扩增,Ot核酸阳性25份,其中14份阳性标本被克隆和测序。同源性和进化分析显示,勐海县14株Ot的groEL区核苷酸同源性为99%～100%,氨基酸同源性均为100%,它们与来自GenBank的BJTZ-OT-O39、AH-GD-OT-S6、UT213、Kato和SH205株之间具有较高的同源性和较近的亲缘关系。17例病例双份血清经IFA检测,其中11例病例的恢复期血清IgG抗体滴度大于急性期血清4倍及以上。根据检测结果,26例病例被诊断为恙虫病（分子诊断15例和血清学诊断11例）。结论首次经血清学及分子生物学证实勐海县存在恙虫病流行。分子流行病学分析表明,勐海县Ot流行株具有稳定的遗传特点和明显的地域特征。

Objective To understand the transmission of scrub typhus in Menghai county,Yunnan province. Methods Blood samples were collected from clinical diagnosed and suspected scrub typhus cases at acute and convalescence phases in Menghai from June to September in 2011. Nested polymerase chain reaction（ nPCR） was conducted to detect the groEL gene of Orientia tsutsugamushi（ Ot） in blood clots from patients at acute phase. Indirect immunofluorescence assays（IFA） were conducted to detect IgG antibodies against Ot in sera from patients. Results A total of 36 blood clot samples were tested with PCR,and 25 samples were positive woth Ot nucleic acid. The groEL gene fragments of 14 positive samples were cloned and then sequenced. According to the homology and phylogenetic analysis; the 14 strains shared 99%- 100% homology of nucleotide and 100% homology of amino acid. They were very close to and shared high homology with the strains BJ-TZ-OT-O39,AH-GD-OT-S6,UT213,Kato and SH205 from GenBank. Of 17 patients detected at both acute phase and convalescence phase,11 had a 4-fold increase in their Ot-IgG titer by IFA.Overall,26 cases were diagnosed with scrub typhus（ 15 molecular biological confirmations and 11 serological confirmations）. Conclusion The serological and molecular biological detections confirmed the transmission of scrub typhus in Menghai. Molecular epidemiological analysis showed that the circulating strains of Ot in Menghai was with stable genetic characteristics and obvious regional characteristics.