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.     

Optimal reactive vaccination strategies for a foot-and-mouth outbreak in the UK

Foot-and-mouth disease (FMD) in the UK provides an ideal opportunity to explore optimal control measures for an infectious disease. The presence of fine-scale spatio-temporal data for the 2001 epidemic has allowed the development of epidemiological models that are more accurate than those generally created for other epidemics and provide the opportunity to explore a variety of alternative control measures. Vaccination was not used during the 2001 epidemic; however, the recent DEFRA (Department for Environment Food and Rural Affairs) contingency plan details how reactive vaccination would be considered in future. Here, using the data from the 2001 epidemic, we consider the optimal deployment of limited vaccination capacity in a complex heterogeneous environment. We use a model of FMD spread to investigate the optimal deployment of reactive ring vaccination of cattle constrained by logistical resources. The predicted optimal ring size is highly dependent upon logistical constraints but is more robust to epidemiological parameters. Other ways of targeting reactive vaccination can significantly reduce the epidemic size; in particular, ignoring the order in which infections are reported and vaccinating those farms closest to any previously reported case can substantially reduce the epidemic. This strategy has the advantage that it rapidly targets new foci of infection and that determining an optimal ring size is unnecessary.     

从猪"高热病"谈我国养殖业亟待解决的问题

就猪“高热病”发生、流行与研究现状进行了简要论述,并结合作者的临床实践与研究提出了几点思考。指出猪“高热病”疫情反映了疫病风险已成为我国养猪业发展之瓶颈,严重制约了畜牧业的发展,必须采取切实可行的政策措施,加大对新发疫病的研究与监控力度,强化防疫意识,改善养殖环境,控制污染,走可持续发展的道路。     

湘西民间畜禽疫病防治知识认知及民间验方

通过个人访谈、集体讨论和问卷调查形式,于2011年7月-9月对湘西自治州7县1市的农户、畜禽养殖大户、乡村兽医及畜禽商贩,就当地土著居民对他们掌握的畜禽疫病防治传统知识和权益分享的意识进行了调查.结果表明,35~55岁年龄土著居民是畜禽疫病防治等传统知识的主要承载着,也是进行畜禽养殖的主要实施者;小规模养殖户主要依靠民族兽药对患病初期的畜禽进行治疗;湘西土著居民虽然掌握着十分重要的畜禽疫病防治的传统知识,但却不知道如何去保护或分享他们的畜禽疫病防治传统知识利益.同时,还根据药性及用途将当地用于治疗和防疫的草药整理归为15类,并列出当地土著居民常用的畜禽疫病诊治10个验方.     

Positive and negative effects of widespread badger culling on tuberculosis in cattle

Human and livestock diseases can be difficult to control where infection persists in wildlife populations. For three decades, European badgers (Meles meles) have been culled by the British government in a series of attempts to limit the spread of Mycobacterium bovis, the causative agent of bovine tuberculosis (TB), to cattle. Despite these efforts, the incidence of TB in cattle has risen consistently, re-emerging as a primary concern for Britain's cattle industry. Recently, badger culling has attracted controversy because experimental studies have reached contrasting conclusions (albeit using different protocols), with culled areas showing either markedly reduced or increased incidence of TB in cattle. This has confused attempts to develop a science-based management policy. Here we use data from a large-scale, randomized field experiment to help resolve these apparent differences. We show that, as carried out in this experiment, culling reduces cattle TB incidence in the areas that are culled, but increases incidence in adjoining areas. These findings are biologically consistent with previous studies but will present challenges for policy development.     

Control dynamics of severe acute respiratory syndrome transmission

Severe acute respiratory syndrome (SARS) is a serious disease with many puzzling features. We present a simple, dynamic model to assess the epidemic potential of SARS and the effectiveness of control measures. With this model, we analysed the SARS epidemic data in Beijing.The data fitting gives the basic case reproduction number of 2.16 leading to the outbreak, and the variation of the effective reproduction number reflecting the control effect. Noticeably, our study shows that the response time and the strength of control measures have significant effects on the scale of the outbreak and the lasting time of the epidemic.     

宋代的牲畜疫病及政府的应对——以宋代政府诏令为中心的讨论

历代政府对耕牛和马都给予了保护性的政策。两宋时期,耕牛和马作为农业生产的主要动力与运输工具,由于国营牧监的南移和饲养方式的变化,导致了疫病的频繁发生和流行,从而引起了宋代政府的高度重视。以宋代政府诏令为中心,探讨宋代牲畜疫病的流行情况及特点,牲畜疫病的病因及对农业生产、交通运输和军事战争所产生的重大影响,分析和疏理宋代通过政府诏令对不同时期发生的牲畜疫病所采取的应对措施。同时,还探讨北宋和南宋政府在牲畜疫病应对上的不同,以及这种不同与两宋时期的政治军事和社会经济之间的关系。     

论动物防疫在西部新农村建设中的问题及对策

社会主义新农村建设离不开畜牧业的健康发展,而加强动物防疫则是畜牧业健康发展的重要保障。西部农村建设中动物防疫工作存在一些问题,包括防疫机构队伍、基层防疫手段和监督手段等方面,相应地,应采取加大经费投入、加强动物防疫体系和队伍建设、加大宣传力度等措施。     

Evolution and molecular epidemiology of foot-and-mouth disease virus in China

Foot-and-mouth disease (FMD),caused by foot-and-mouth disease virus (FMDV),is considered one of the most important viral diseases of cloven-hoofed animals,causing severe economic losses in affected regions of the world.Three serotypes (A,O,and Asia 1) of FMDV have been identified in China since 1958.In addition,the occurrence of novel subtypes within these serotypes has made the epidemiology of FMDV more complicated over the last few years.In this review,we summarize the history and the current epidemiological situation in China,genetic diversity (e.g.,quasispecies dynamics,antigenic heterogeneity,and functional constraints),intertypic recombination,and the evidence for positive selection of different FMDV serotypes.We also assess these genetic data to understand the origin,evolution,and transmission of FMDV,the findings of which may be useful in developing control measures for future epidemics.     

浅谈农养畜禽的春秋防疫

针对农养畜禽春秋防疫中出现的问题，提出了一些注意事项及防范措施。     

永胜县血吸虫病流行病学抽样调查工作报告

目的：准确掌握永胜县血吸虫病流行现状，为制订血吸虫病防治策略提供依据。方法：用分层随机抽样法确定调查点。用尼龙袋集卵孵化法、顶管孵化法分别对人畜进行查病，用系统抽样结合环境抽样法开展螺情调查。结果：人群感染率为3．74％；家畜感染率为1．59％；活螺平均密度为3．5只／框，钉螺自然感染率为0．026％，感染螺平均密为0．0009只／框。结论：重度流行区疫情有了大幅度的下降，轻度流行区的疫情有一定的反弹。     

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.     

Large-scale eradication of rabies using recombinant vaccinia-rabies vaccine.

Rabies infection of domestic and wild animals is a serious problem throughout the world. The major disease vector in Europe is the red fox (Vulpes vulpes) and rabies control has focused on vaccinating and/or culling foxes. Culling has not been effective, and the distribution of five vaccine baits is the only appropriate method for the vaccination of wild foxes. Although some European countries have conducted field vaccination campaigns using attenuated rabies virus strains, their use has not been extensively approved because they retain pathogenicity for rodents and can revert to virulence. These strains cannot be used in North America because they are pathogenic for the striped skunk (Mephitis mephitis) and are ineffective in the raccoon (Procyon lotor). We have constructed a recombinant vaccinia virus, VVTGgRAB, expressing the surface glycoprotein (G) of rabies virus (ERA strain). The recombinant was a highly effective vaccine in experimental animals, in captive foxes and in raccoons. We report here the results of a large-scale campaign of fox vaccination in a 2,200 km2 region of southern Belgium, an area in which rabies is prevalent. After distribution, 81% of foxes inspected were positive for tetracycline, a biomarker included in the vaccine bait and, other than one rabid fox detected close to the periphery of the treated area, no case of rabies, either in foxes or in domestic livestock, has been reported in the area.     

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).     

Cattle movements and bovine tuberculosis in Great Britain

For 20 years, bovine tuberculosis (BTB) has been spreading in Great Britain (England, Wales and Scotland) and is now endemic in the southwest and parts of central England and in southwest Wales, and occurs sporadically elsewhere. Although its transmission pathways remain poorly understood, the disease's distribution was previously modelled statistically by using environmental variables and measures of their seasonality. Movements of infected animals have long been considered a critical factor in the spread of livestock diseases, as reflected in strict import/export regulations, the extensive movement restrictions imposed during the 2001 foot-and-mouth disease outbreak, the tracing procedures after a new case of BTB has been confirmed and the Government's recently published strategic framework for the sustainable control on BTB. Since January 2001 it has been mandatory for stock-keepers in Great Britain to notify the British Cattle Movement Service of all cattle births, movements and deaths. Here we show that movements as recorded in the Cattle Tracing System data archive, and particularly those from areas where BTB is reported, consistently outperform environmental, topographic and other anthropogenic variables as the main predictor of disease occurrence. Simulation distribution models for 2002 and 2003, incorporating all predictor categories, are presented and used to project distributions for 2004 and 2005.     

具捕杀效应的SEI狂犬病模型的空间动力学分析

为讨论针对性的捕杀对狂犬病传播的影响,研究了一类具捕杀效应的易感者-潜伏期感染者-已经感染者(SEI)狂犬病模型.通过相应的特征值问题,引入基本再生数,并利用上下解方法建立了平衡点的稳定性.结果表明:有针对性的捕杀对狂犬病的控制和预防起着重要的作用.     

人工智能助力新冠肺炎疫情防控的实践情景

 分析了人工智能助力新冠肺炎疫情防控的实践情境,主要包括疫情监测预警、医疗诊断、病毒及药物研发等。人工智能技术的应用对控制疫情传播范围、缓解诊疗压力、提升研发效率等具有显著效果。根据人工智能助力疫情防控上面临的法规伦理、数据安全、算法偏见等现实难题,提出完善法律法规、保障数据安全、加强人才培养等发展建议。     

论疫病防控：决策问题、思维和标准

 通过对中国防控新型冠状病毒肺炎疫情相关情况的观察和反思，提出了疫病防控决策须考虑的主要问题，认为疫病防控应有可传染性思维、流行病学思维、成本-效果思维、爱心抗疫思维、疫期法治思维等5种思维，主张建立疫情早期防控和失控阶段防控两套标准，以期辅助科学决策、理性施策，有效减轻疫情发展及防控带来的生命财产和经济社会损失。     

病毒性肝炎——值得警惕的重要人兽互传病

概述了人类病毒性肝炎的发病特点及流行状况、动物模型和自然感染病毒性肝炎的情况。简述了笔者的研究室在动物病毒性肝炎方面的研究进展。引起人类病毒性肝炎的病因复杂多样,病毒性肝炎严重地威胁着人类的健康。尤其是随着时间的推移,人类病毒性肝炎的发病率在不断提高,作为一种人兽互传病——病毒性肝炎已在动物中广泛存在,尤其是在畜禽中的分布,是我们不可回避的事实。人类病毒性肝炎的蔓延速度之所以如此之快,可能与动物有关,特别是与人类生活关系比较密切的家畜和家禽有关。动物病毒性肝炎的存在已对公共卫生造成显著影响,对人类健康构成严重威胁。建议相关主管部门重视对病毒性肝炎的研究工作,从公共卫生的角度组织研究动物,特别是畜禽病毒性肝炎与人的病毒性肝炎之间的关系问题,尤其是其间的传播问题,为防制此类疾病的进一步蔓延、流行,保证动物产品的卫生安全,保障人类的健康提供科学依据,并尽快采取防控措施。     

Impact of localized badger culling on tuberculosis incidence in British cattle

Pathogens that are transmitted between wildlife, livestock and humans present major challenges for the protection of human and animal health, the economic sustainability of agriculture, and the conservation of wildlife. Mycobacterium bovis, the aetiological agent of bovine tuberculosis (TB), is one such pathogen. The incidence of TB in cattle has increased substantially in parts of Great Britain in the past two decades, adversely affecting the livelihoods of cattle farmers and potentially increasing the risks of human exposure. The control of bovine TB in Great Britain is complicated by the involvement of wildlife, particularly badgers (Meles meles), which appear to sustain endemic infection and can transmit TB to cattle. Between 1975 and 1997 over 20,000 badgers were culled as part of British TB control policy, generating conflict between conservation and farming interest groups. Here we present results from a large-scale field trial that indicate that localized badger culling not only fails to control but also seems to increase TB incidence in cattle.