海南省琼中黎族苗族自治县2019年恙虫病东方体分子流行病学及遗传进化分析

Epidemiology and genome analysis of scrub typhus in Qiongzhong,Hainan,2019

目的通过分析海南省琼中黎族苗族自治县(简称“琼中”)98例不明原因发热患者的恙虫病流行特点,了解该地区恙虫病东方体菌株流行的情况,为该地区制定恙虫病防治策略和控制措施提供科学依据。方法收集2019年1月1日至2019年12月31日琼中黎族苗族自治县人民医院诊断为疑似恙虫病和不明原因发热患者血液样本,利用胶体金免疫层析法和巢式PCR方法对样本进行恙虫病东方体特异性IgM、IgG抗体和恙虫病东方体56kD型特异性抗原基因检测,同时使用预先设计的样本信息表收集患者的临床表现及流行病学信息。针对巢式PCR检测结果为阳性的样本,进行克隆及Sanger测序。对获得的患者临床信息及检测结果进行流行病学分析,将测序得到的序列进行基因遗传进化分析。结果98例样本中,恙虫病IgM抗体阳性率为24.49%(24/98),恙虫病IgG抗体阳性率为46.94%(46/98),恙虫病PCR阳性率26.53%(26/98),焦痂或皮疹13.27%(13/98)。根据诊断标准,最终诊断为恙虫病的患者为33例。感染人群主要以31~50岁的青壮年为主,职业主要为农民。该地区恙虫病的流行以营根镇、长征镇和红毛镇为主并涉及9个乡镇。流行时间有明细的季节性,以7月和11月为主要高发期。流行的基因型主要为Karp型和Gilliam型。结论琼中为恙虫病的自然疫源地,该地区流行的恙虫病东方体基因型主要为Karp和Gilliam型,具有基因多态性。

ObjectiveTo analyze the epidemiological characteristics and genome features of scrub typhus in 98 patients with unexplained fever in Qiongzhong Li Miao Autonomous County and provide guidance for local scrub typhus prevention and control.MethodsBlood samples from the patients with clinically diagnosed suspected scrub typhus or acute undifferentiated fever were collected from People's Hospital of Qiongzhong Li Miao Autonomous County,Hainan,between 1st January and 31th December 2019.Orientia tsutsugamushi-specific IgM/IgG antibodies and DNA were detected by colloidal gold immunochromatography and nested PCR on the patients'serum samples.Positive-PCR products were further verified by Sanger sequencing.The epidemiological characteristics of the laboratory-confirmed cases were recorded using a predesigned database.Epidemiological and phylogenetic analysis was carried out on the obtained sample information and test results.ResultsIn total,98 patients with suspected scrub typhus or acute febrile illness were acquired.The positive rates of IgM and IgG were 22.49%(24/98)and 46.49%(46/98),respectively,and the positive rate of PCR was 26.53%(26/98),with eschar or rash 13.27%(13/98).By case definition,33 patients were diagnosed with scrub typhus.The adults aged 31 to 50 years,the patients mainly were farmers.The patients resided in 9 towns or countryside of Qiongzhong County,and three of the highest number of cases being reported among residents in Yinggen town,Changzhen town,and Hongmao town.Seasonal variations in the incidence rate of scrub typhus were observed,with the peak incidence occurring in July and November.Two genotypes of Orientia tsutsugamushi were identified among these patients,including Karp and Gilliam.The predominant genotype was Karp and Gilliam.ConclusionsThe findings suggested that scrub typhus is an endemic disease in Qiongzhong,the genotype of Orientia tsutsugamushi epidemic in this area is mainly Karp type and Gilliam type,with gene polymorphism.