四川大山区血吸虫病传播动力学及控制的研究

目的 利用数学流行病学和计算机模拟方法研究山区血吸虫病的传播因素及其控制策略.方法 基于在四川西昌20个村的血吸虫病流行病学调查,建立基于本地传播因素的血吸虫病传播模型.利用蒙特卡罗模拟对模型进行模拟,采用二分法用3个村的数据来效验模型,并用经效验的模型来分析在3种控制策略下本地血吸虫病传播的趋势.结果 现场调查显示以村为单位的人群血吸虫病感染率和感染强度分别在3%～73%和平均克粪虫卵数(epg)在0.1至100.0之间.流行因素包括居民职业、疫水接触、微环境参数(气温、降雨),被整合入模型中.经二分法效验的模型预测显示连续化疗(50%～60%的覆盖率)在6年内能将感染强度降低30%～80%,但不能降低传播潜力;所以化疗一旦停止,传播即反弹.持续的局部的环境干预,如灭螺和虫卵控制(30%～50%覆盖率),可以将传播控制在半稳定水平;只有持续的包括化疗和环境干预在内的综合控制,在5～10年间才能将传播控制到很低的水平,甚至阻断传播.结论 利用传播模型结合现场数据能够帮助分析影响血吸虫病本地传播的因素,并帮助制定相应的控制策略;血吸虫病的控制应建立在对本地因素的认识和可持续的环境干预基础上.

Modeling transmission dynamics and control of schistosomiasis in the mountainous region,Sichuan

Objective To use a mathematical model and computer simulation to study transmission dynamics and control of schistosomiasis in mountainous regions of Sichuan.Methods Based on studies of schistosomiasis iaponica transmission in 20 villages in mountainous regions of Sichuan,a mathematical model Was developed to characterize the impaet of lOCal environIllental factors on transmission intensity.The model integrated site-speific factors and was calibrated to field epidemiological data from 3 subset villages.The dichotomic method was then used to predict different control measures.Results The study showed hish variations in prevalence of infection and infection intensity across villages,ranging between 3%-73%,0.1-100 epg(eggs per gram stool),respectively.Important factors including occupation of local residents,exposure to contaminated water,microclimatic characteristics were integrated in the model.The predictions of dichotomic models showed that continuing chemotherapy(coverage between 50%-60%)could reduce infection intensifies to 30%-80%,but could not change local transmission potential;therefore,the termination of chemotherapy would be foilowed bv bouncing back of transmission.Sustaining targeted environnlental interventions through snail and parasite oval contrel at certain coverage(30%-50%,respectively)could reduce the transmission to relatively stable levels.The model predictions showed that an integrated control(e.g.including both chemotherapy and environmental interventions)could suppress the transmission to an undeteetable level even interruption of transmission between 5-10 years.Conclusion The study demonstrated the feasibility of using a dynamic model,calibrated to local data,to gain insights into complicated processes underlying the transmission and informing site-specific control strategies.