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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 epidemic situation of scrub typhus in Menghai County, Yunnan Province. Methods Blood samples were collected from clinical diagnosis and suspected cases of tsutsugamushi disease in acute and convalescent cases in Menghai County, China in June, 2011. The nocturnal polymerase chain reaction (nPCR) Amplification and sequencing of groEL gene. Serum Ot-IgG antibodies were detected by indirect immunofluorescence assay (IFA). Results Thirty - six cases of acute clot specimens were amplified by polymerase chain reaction (PCR). Among them, there were 25 positive Ot nucleic acids. Among them, 14 positive samples were cloned and sequenced. Homology and phylogenetic analysis showed that the nucleotide and amino acid identities of the groEL region from 14 Ot in Menghai County were 99% -100% and 100% respectively. Their homology with BJTZ-OT-O39 from GenBank, AH-GD-OT-S6, UT213, Kato and SH205 strains have higher homology and closer genetic relationship. Serum IgG antibody titers of convalescent sera from 11 cases were more than 4 times higher than those of acute phase in 17 cases of double sera detected by IFA. According to the test results, 26 cases were diagnosed as tsutsugamushi disease (molecular diagnosis of 15 cases and serological diagnosis of 11 cases). Conclusions The first epidemic of scrub typhus in Menghai County was confirmed by serological and molecular biology. Molecular epidemiological analysis showed that the epidemic strains of Ot in Menghai County had stable genetic characteristics and obvious geographical features.