一起由榕透翅毒蛾幼虫引起皮炎暴发的流行病学调查

An epidemiological survey of a caterpillar dermatitis outbreak caused by Perina nuda

目的查明某小学皮炎暴发事件的致病因子、感染途径及危险因素,为疫情防控提供依据。方法根据疾病特点制定病例定义,在学校和附近的社区健康服务中心搜索可疑病例,利用自行设计的调查表,对病例开展个案调查,对学校内外环境实地调查,利用回顾性队列研究分析验证暴露危险因素,现场捕获毒蛾幼虫进行鉴定。结果共发现28例病例,主要临床症状为皮肤瘙痒、斑丘疹。首发病例于4月5日发病,从5月开始,陆续有散在病例出现,5月25日出现21例病例,且均为5年级3班学生和辅导员,之后再无病例出现,流行曲线显示此次暴发为点源暴发的单峰模式。其中学生21人,辅导员6人,清洁工1人;五(3)班15例,罹患率25.42%,一(2)班4例,罹患率6.82%,一(1)班2例,罹患率3.35%,班级分布差异有统计学意义(c2=16.09,P<0.01)。回顾性队列研究结果显示搬塑料凳(RR=17.95,95%CI:4.50~70.00)以及树下逗留(RR=+∞,95%CI:3.80~∞)为感染危险因素。经鉴定本次捕获的毒蛾幼虫为榕透翅毒蛾幼虫。结论本次皮炎爆发疫情为病人接触到凳子上及散落的毒蛾幼虫刚毛所致。

Objective To investigate the cause,the route and the related risk factors of a dermatitis outbreak in a primary school and provide evidence for its control&prevention.Methods Case definition was based on disease characteristics.Suspicious cases were searched in schools and nearby community health services.Cases were investigated by self-designed questionnaires.Field survey of the environment inside and outside the school was performed.Retrospective cohort analysis was used to verify exposure risk factors.Field larvae were captured for identification.Results A total of 28 cases were found.The main clinical symptoms were pruritus and maculopapular rash.The first case occurred on April 5 th.Since May,there had been scattered cases.There were 21 cases on May 25,all of which were students and counsellors in Grade 5 and class 3.The epidemic curve shows that the outbreak was a unimodal pattern of point source outbreaks including were 21 students,6 counselors,and 1 cleaner.15 cases were in Grade 5 class 3.with attack rate of 25.42%;4 cases were in Grade1 class 2.with attack rate of 6.82%;2 cases were in Grade 1 class 1,with the attack rate of 3.35%.The difference in class distribution was statistically significant(χ~2=16.09,P<0.01).The results of the retrospective cohort study showed that moving plastic stools(RR=17.95,95%CI:4.50-70.0)and stays under the tree(RR=+∞,95%CI:3.80-∞)-were risk factors for infection.It was identified that the trapped larvae of the poisonous moth were larvae of the Perina nuda.Conclusion The dermatitis outbreak was caused by the patient’s contact with stools and scattered poisonous moth larvae.