Modelling vaccination strategies against foot-and-mouth disease

Vaccination has proved a powerful defence against a range of infectious diseases of humans and animals. However, its potential to control major epidemics of foot-and-mouth disease (FMD) in livestock is contentious. Using an individual farm-based model, we consider either national prophylactic vaccination campaigns in advance of an outbreak, or combinations of reactive vaccination and culling strategies during an epidemic. Consistent with standard epidemiological theory, mass prophylactic vaccination could reduce greatly the potential for a major epidemic, while the targeting of high-risk farms increases efficiency. Given sufficient resources and preparation, a combination of reactive vaccination and culling might control ongoing epidemics. We also explore a reactive strategy, 'predictive' vaccination, which targets key spatial transmission loci and can reduce markedly the long tail that characterizes many FMD epidemics. These analyses have broader implications for the control of human and livestock infectious diseases in heterogeneous spatial landscapes.     

Transmission intensity and impact of control policies on the foot and mouth epidemic in Great Britain

The foot and mouth disease (FMD) epidemic in British livestock remains an ongoing cause for concern, with new cases still arising in previously unaffected areas. Epidemiological analyses have been vital in delivering scientific advice to government on effective control measures. Using disease, culling and census data on all livestock farms in Great Britain, we analysed the risk factors determining the spatiotemporal evolution of the epidemic and of the impact of control policies on FMD incidence. Here we show that the species mix, animal numbers and the number of distinct land parcels in a farm are central to explaining regional variation in transmission intensity. We use the parameter estimates thus obtained in a dynamical model of disease spread to show that extended culling programmes were essential for controlling the epidemic to the extent achieved, but demonstrate that the epidemic could have been substantially reduced in scale had the most efficient control measures been rigorously applied earlier.     

口蹄疫病毒持续感染的研究进展

口蹄疫病毒(foot-and-mouth disease virus,FMDV)能引起偶蹄动物患一种名为口蹄疫(foot-and-mouth disease,FMD)的高度接触性、发热性、急性的传染病.FMD的大规模爆发会导致整个国家或地区的动物和动物相关制品产量降低、贸易受限,造成巨大的经济损失.FMDV持续感染是造成FMDV容易蔓延并难以根除的重要原因.该文综述了FMDV持续感染期间病毒在体内的存在位置与感染特性,并以病毒与宿主细胞、宿主免疫系统之间的相互作用为重点,介绍了持续感染相关机制研究进展,总结了疫情防控相关策略,以期为解决FMDV持续感染问题提供参考.     

Veterinary epidemiology: vaccination strategies for foot-and-mouth disease

When foot-and-mouth disease struck the United Kingdom in 2001, the traditional 'stamping out' policy of 1967-68 was supplemented by the pre-emptive culling of animals in premises contiguous to infected premises. A model proposed by Tildesley et al. indicates that the introduction of vaccination should at least halve the number of premises that would need to be subjected to culling in the event of another outbreak. We contest, however, that the overlapping confidence intervals of the outputs of their model, and the inconsistency of their results compared with those from previous models, call into question the model's value as a decision tool, while adding little to the recognized tenet of ring vaccination.     

一类脉冲接种时滞SEIRS传染病模型的动力学分析(英文)

研究了一类脉冲接种和总人口变化的时滞SEIRS传染病模型.结果显示,当R1<1时无病周期解是全局吸引的,当R2>1时疾病是持续的.     

蛋鸡传染性鼻炎的综合防治措施

通过多年蛋鸡生产实践、血清学检测，掌握了鸡传染性鼻炎疫情；通过合理的疫苗接种，结合科学饲养管理，实施严密的生物安全、卫生、消毒制度、药物治疗等综合防治措施，取得较好的防疫效果，促进了蛋鸡正常生长与生产。     

SEIR-SW,Simulation Model of Influenza Spread Based on the Small World Network

This study modeled the spread of an influenza epidemic in the population of Oran, Algeria. We investigated the mathematical epidemic model, SEIR(Susceptible-Exposed-Infected-Removed), through extensive simulations of the effects of social network on epidemic spread in a Small World(SW) network, to understand how an influenza epidemic spreads through a human population. A combined SEIR-SW model was built, to help understand the dynamics of infectious disease in a community, and to identify the main characteristics of epidemic transmission and its evolution over time. The model was also used to examine social network effects to better understand the topological structure of social contact and the impact of its properties. Experiments were conducted to evaluate the combined SEIR-SW model. Simulation results were analyzed to explore how network evolution influences the spread of desease, and statistical tests were applied to validate the model. The model accurately replicated the dynamic behavior of the real influenza epidemic data, confirming that the susceptible size and topological structure of social networks in a human population significantly influence the spread of infectious diseases. Our model can provide health policy decision makers with a better understanding of epidemic spread,allowing them to implement control measures. It also provides an early warning of the emergence of influenza epidemics.     

一类具有Logistic死亡率的脉冲免疫接种SIRS传染病模型

建立了一类具有一般Logistic死亡率和标准传染率的SIRS传染病模型, 在脉冲免疫接种条件下, 利用离散动力系统的频闪映射方法, 得到了系统的无病周期解. 运用Floquet乘子理论和脉冲微分方程比较定理, 证明了该周期解的全局渐近稳定性, 并获得了系统一致持续生存的条件. 结果表明, 为了阻止疾病流行, 需要选择恰当的脉冲接种率和脉冲免疫接种周期.     

具有脉冲接种的SIR传染病模型的优化控制

将最优脉冲控制原理应用到具有脉冲接种的SIR传染病模型，使治疗费用和接种费用最省，并给出求最优接种量和最优接种周期的充要条件．     

具有饱和接种率的传染病模型的稳定性

考虑到实践中有一部分人不愿意接种疫苗,引入1个阈值参数,建立了1个具有饱和接种率的传染病模型,以刻画资源有限情况下的接种策略。定义了模型的基本再生数,讨论了无病平衡点和地方病平衡点的存在性以及全局稳定性。结果表明:一方面人群中不愿接种者的比例影响疾病的消除与否以及不能消除时染病者的比例;另一方面可以适当增加存储疫苗的数量,使得当疾病不能被消除时,染病者的数量可以稳定在一个医疗条件允许的预先设定的水平。     

基于 SIR 传染病模型的印度新冠疫情波及影响分析

针对印度新型冠状病毒肺炎(COVID-19)疫情的传播,建立通过设定目标函数求最优解来确定模型未知参数的 SIR 传染病动力学模型。 首先通过线性回归拟合参数范围,设定目标函数作为约束条件,结合龙格-库塔法,借助 Matlab 软件确定参数值最优解,进行 SIR 模型拟合和预测,发现印度疫情拐点将出现在 2021 年 5 月 8 日左右,结合预测数据推导未来每日新增及累计新增病例数,虽未来 100 d 内将持续出现新增病例,但疫情现期已经有消退趋势;其次考虑印度变种病毒 B. 1. 617 以及当下疫苗接种情况的影响,建立加入疫苗影响因素的 SIR 预测模型,通过进行疫苗接种灵敏度分析模拟出印度疫苗接种率大约需要达到 75%,考虑有效保护率则接种率需要高达 95%,才可以建立起群体免疫屏障;最后通过基本传染数验证了疫苗接种率,并对新冠波及影响做出了相应对策分析。     

具有饱和接触率的SIQRS预防接种模型的控制策略

建立并分析一类具有饱和接触率、 隔离项和脉冲预防接种的SIQRS传染病模型. 通过综合运用Floquet定理、 脉冲微分不等式和极限系统理论, 获得了保证SIQRS传染病模型的无病周期解全局渐近稳定的阈值条件. 通过比较脉冲预防接种和隔离两种控制策略的有效性, 表明同时使用脉冲预防接种和隔离两种策略比单独应用一种策略更有效.     

暴发性鸭瘟的诊断

通过对四川德阳地区某养殖场的发病种鸭的流行病学调查，临床观察。病理剖检。病原分离及聚合酶链式反应确诊该养殖场鸭群暴发鸭瘟：并针对其场地的具体情况提出了相应的防疫建议。     

一类流行病模型的最优接种策略

研究一类具有年龄结构的流行病动力系统的最优预防接种问题，借助法锥技巧获得了传染病控制问题的Pontryagin极值原理。     

基于SIR传染病模型的不同控制策略比较

研究了SIR模型在连续接种、脉冲接种、治疗等不同策略下平衡点的稳定性,获得了疾病灭绝的阈值条件.通过比较各种控制策略的有效性,说明接种比治疗更能有效控制疾病,同时应用两种控制策略比单独应用一种更有效.     

一类有限资源下的非光滑传染病模型

目的研究有限医疗资源对接种策略及传染病预防控制的影响。方法引入阈值控制策略到经典传染病模型中,建立非光滑传染病模型,刻画如下具有阈值水平的接种策略:当易感人数超过阈值水平时,实施常数接种策略,否则实施与易感人数成正比的接种策略。在子系统动力学研究的基础上,对非光滑系统进行研究。结果得到了非光滑系统规则平衡态和广义平衡态的稳定性。结论当疾病不能清除时,选取适当的控制参数可使染病人数最终控制在给定水平。     

The abundance threshold for plague as a critical percolation phenomenon

Percolation theory is most commonly associated with the slow flow of liquid through a porous medium, with applications to the physical sciences. Epidemiological applications have been anticipated for disease systems where the host is a plant or volume of soil, and hence is fixed in space. However, no natural examples have been reported. The central question of interest in percolation theory, the possibility of an infinite connected cluster, corresponds in infectious disease to a positive probability of an epidemic. Archived records of plague (infection with Yersinia pestis) in populations of great gerbils (Rhombomys opimus) in Kazakhstan have been used to show that epizootics only occur when more than about 0.33 of the burrow systems built by the host are occupied by family groups. The underlying mechanism for this abundance threshold is unknown. Here we present evidence that it is a percolation threshold, which arises from the difference in scale between the movements that transport infectious fleas between family groups and the vast size of contiguous landscapes colonized by gerbils. Conventional theory predicts that abundance thresholds for the spread of infectious disease arise when transmission between hosts is density dependent such that the basic reproduction number (R(0)) increases with abundance, attaining 1 at the threshold. Percolation thresholds, however, are separate, spatially explicit thresholds that indicate long-range connectivity in a system and do not coincide with R(0) = 1. Abundance thresholds are the theoretical basis for attempts to manage infectious disease by reducing the abundance of susceptibles, including vaccination and the culling of wildlife. This first natural example of a percolation threshold in a disease system invites a re-appraisal of other invasion thresholds, such as those for epidemic viral infections in African lions (Panthera leo), and of other disease systems such as bovine tuberculosis (caused by Mycobacterium bovis) in badgers (Meles meles).     

具有连续接种和治疗的SIRS传染病模型的全局稳定性

建立并分析了一类具有标准发生率、垂直传染、连续接种和治疗的SIRS传染病模型.综合运用RouthHurwitz判据、LaSalle不变集原理和广义Bendixson-Dulac定理,获得了保证SIRS传染病模型的无病平衡点和地方病平衡点全局渐近稳定性的阀值条件.通过比较两种控制策略的有效性,说明同时使用接种和治疗两种策略比单独应用一种更有效.     

基于SIRS传染病模型的不同控制策略比较

建立并分析了一类具有标准发生率、垂直传染、连续接种和治疗的SIRS传染病模型.综合运用RouthHurwitz判据、La Salle不变集原理和广义Bendixson-Dulac定理,获得了保证SIRS传染病模型的无病平衡点和地方病平衡点全局渐近稳定的阈值条件.通过比较两种控制策略的有效性,说明同时使用接种和治疗两种策略比单独应用一种更有效.     

一类具有迁移特性的生物危险源扩散动力学模型分析

为了解决人口迁移带来的传染病防治问题,以人口相互迁移的两个城市为例,建立了传染率为双线性的SIR模型,通过脉冲接种对疾病进行预防和控制,求出了该模型的无病周期解和疾病消亡的阈值,并分别利用Fioquet定理和脉冲微分不等式证明了无病周期解的局部稳定性和全局稳定性,最后借助Matlab仿真加以验证.研究结果表明,脉冲接种不仅可以极大地减少患病者的人数,而且能够缩短疾病流行时间.