Objective To study the epidemiological and etiological characteristics of typhoid and paratyphoid fever in high epidemic areas. Methods Reported data on typhoid and paratyphoid fever during 1988- 2007 in Ningbo were analyzed epidemiologically. Shellfish from the market was collected for laboratory testing and ,Salmonella typhi strains collected from the patients were also studied. Results Number of reported cases on both typhoid and paratyphoid fever was 19 404 with 7 deaths, from 1988 to 2007. The annual mean incidence was 17.68 per one hundred thousand with the fatality rate as 0.36 per thousand. Most cases were among adults aged 20-50 years and an obvious regional distribution was observed with high incidence seen in winter and spring. Since 1990s, the advantage strain had changed from Salmonella typhi to Salmonella paratyphi A. Etiologic studies showed that raw Anadara subcrenata and oyster were the main risk factors. One Salmonella paratyphi A strain was detected in both Anadara subcrenata and oysters collected from the market, which contained TEM-1 drug resistance gene. PFGE genotyping showed that PFGE-X2 was the strain which causing pandemic in Ningbo. Conclusion Eating contaminated raw shellfish like oysters and hairy clams was the primary risk factor, responsible for the outbreaks. Salmonella paratyphi A was the advantages pandemic strain in Ningbo. Strategies as supervision on personal hygiene and health education should be strengthened.%目的 探讨伤寒副伤寒高发地区的流行病学和病原学特征.方法 运用描述流行病学与分析流行病学对1988-2007年伤寒副伤寒疫情资料和暴发资料进行分析.采集市场贝壳类海产品进行污染情况检测,并对患者中分离到的菌株进行实验室系统研究.结果 1988-2007年全市累计报告伤寒副伤寒病例19 404例,死亡7例,年平均发病率为17.68/10万,病死率为0.36‰.发病呈现周期性波动,冬春季高发,且存在明显地区聚集性,发病以20～50岁年龄的青壮年为主.流行菌株以甲型剐伤寒沙门菌为主.传播因素调查分析显示,居民生吃毛蚶和牡蛎是造成伤寒副伤寒高发的主要危险因素;同时从市场所采集的毛蚶和牡蛎中,各检出1株甲型副伤寒沙门菌,并带有TEM-1型耐药基因.甲型副伤寒沙门菌在海产品牡蛎中存活观察试验证实菌株在带壳牡蛎活体水体中至少能存活10 d以上.PFGE基因分型表明,X2型是宁波地区甲型副伤寒优势流行株.结论 宁波地区居民生吃毛蚶和牡蛎是造成伤寒副伤寒高发的丰要危险因素,加强对贝壳类海产品的卫生监督管理和对居民的健康教育是预防控制伤寒副伤寒的关键措施.
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