A Review of Simulation Modelling Approaches Used for the Spread of Zoonotic Influenza Viruses in Animal and Human Populations

Increasing incidences of emerging and re‐emerging diseases that are mostly zoonotic (e.g. severe acute respiratory syndrome, avian influenza H5N1, pandemic influenza) has led to the need for a multidisciplinary approach to tackling these threats to public and animal health. Accordingly, a global movement of ‘One‐Health/One‐Medicine’ has been launched to foster collaborative efforts amongst animal and human health officials and researchers to address these problems. Historical evidence points to the fact that pandemics caused by influenza A viruses remain a major zoonotic threat to mankind. Recently, a range of mathematical and computer simulation modelling methods and tools have increasingly been applied to improve our understanding of disease transmission dynamics, contingency planning and to support policy decisions on disease outbreak management. This review provides an overview of methods, approaches and software used for modelling the spread of zoonotic influenza viruses in animals and humans, particularly those related to the animal‐human interface. Modelling parameters used in these studies are summarized to provide references for future work. This review highlights the limited application of modelling research to influenza in animals and at the animal‐human interface, in marked contrast to the large volume of its research in human populations. Although swine are widely recognized as a potential host for generating novel influenza viruses, and that some of these viruses, including pandemic influenza A/H1N1 2009, have been shown to be readily transmissible between humans and swine, only one study was found related to the modelling of influenza spread at the swine‐human interface. Significant gaps in the knowledge of frequency of novel viral strains evolution in pigs, farm‐level natural history of influenza infection, incidences of influenza transmission between farms and between swine and humans are clearly evident. Therefore, there is a need to direct additional research to the study of influenza transmission dynamics in animals and at the animal‐human interface.     

Zoonoses as a risk when associating with livestock or animal products

The risk of zoonotic disease transmission when handling livestock or animal products is substantial. In industrialized countries, the classical zoonotic diseases such as tuberculosis or brucellosis are no longer in the foreground. Latent zoonoses such as salmonellosis and campylobacteriosis can cause serious disease in humans and have become a major public health problem during the past years. Since animals infected with these pathogens show only mild transient disease or no clinical signs at all, new concepts in the entire production line ("stable to table") are necessary in order to avoid human infection. Two emerging viruses with zoonotic potential--avian influenza virus and Nipah virus--have been found in Asia in 1997 and 1999. Both diseases had a major impact on disease control and public health in the countries of origin. In order to cope threats from infectious diseases, in particular those of public health relevance, a combined effort among all institutions involved will be necessary. The proposed "European Center for Infectious Diseases" and the "Swiss center for zoonotic diseases" could be a potential approach in order to achieve this goal.     

Reports of zoonotic disease outbreaks associated with animal exhibits and availability of recommendations for preventing zoonotic disease transmission from animals to people in such settings

OBJECTIVE: To assess the number of zoonotic disease outbreaks associated with animal exhibits and identify published recommendations for preventing zoonotic disease transmission from animals to people in exhibit settings. DESIGN: Literature review and survey of state public health veterinarians and state epidemiologists. PROCEDURE: MEDLINE and agriculture databases were searched from 1966 through 2000. Retrieved references and additional resources provided by the authors were reviewed. A survey was sent to state public health veterinarians and state epidemiologists to determine whether their states had written recommendations or guidelines for controlling zoonotic diseases in animal exhibition venues, whether their states maintained a listing of animal exhibitors in the state, and whether they had any information on recent outbreaks involving animals in exhibitions. RESULTS: 11 published outbreaks were identified. These outbreaks occurred in a variety of settings including petting zoos, farms, and a zoological park. An additional episode involving exposure to a potentially rabid bear required extensive public health resources. A survey of state public health veterinarians identified 16 additional unpublished outbreaks or incidents. Most states did not have written recommendations or guidelines for controlling zoonotic diseases or any means to disseminate educational materials to animal exhibitors. CONCLUSIONS: Recent outbreaks of zoonotic diseases associated with contact with animals in exhibition venues highlight concerns for disease transmission to public visitors. Only a handful of states have written guidelines for preventing zoonotic disease transmission in animal exhibition venues, and published recommendations currently available focus on preventing enteric diseases and largely do not address other zoonotic diseases or prevention of bite wounds.     

Control and prevention of emerging zoonoses

Emerging and re-emerging zoonoses are zoonotic diseases caused by either totally new or partially new agents or by microorganisms previously known but now occurring in places or in species where the disease was previously unknown. Zoonotic diseases account for the majority of all emerging infectious diseases. Several factors have led to the emergence of these infections, including human demographics, the industrialization of food production, globalization, international travel and commerce, land use, microbial adaptation, and changes and breakdown in public health measures. Several zoonotic agents are also potential agents that could be used as biological weapons. The recent use of anthrax spores in tainted mall in the US underlines our need for preparedness against bioterrorism. Prevention and control of these emerging zoonotic diseases is based on recognition, investigation, and collaboration, the development of advanced diagnosis and surveillance tools, the use of applied epidemiology and molecular biology methods, as well as education, information, communication, and technology transfer.     

Contingency planning: preparation of contingency plans

Outbreaks of infectious animal diseases such as foot-and-mouth disease, classical swine fever, Newcastle disease and avian influenza may have a devastating impact, not only on the livestock sector and the rural community in the directly affected areas, but also beyond agriculture and nation wide. The risk of introducing disease pathogens into a country and the spread of the agent within a country depends on a number of factors including import controls, movement of animals and animal products and the biosecurity applied by livestock producers. An adequate contingency plan is an important instrument in the preparation for and the handling of an epidemic. The legislation of the European Union requires that all Member States draw up a contingency plan which specifies the national measures required to maintain a high level of awareness and preparedness and is to be implemented in the event of disease outbreak. This paper describes the main elements to be included in the contingency plans submitted by Member States to the European Commission for approval.     

Zoonotic disease awareness survey of backyard poultry and swine owners in southcentral Pennsylvania

Owners of small backyard poultry and swine operations may be at higher risk of zoonotic diseases due to husbandry inexperience and/or a lack of knowledge. Backyard poultry and swine owners in southcentral Pennsylvania were surveyed regarding their knowledge and attitudes towards zoonotic disease prevention. One hundred and six backyard poultry and/or swine owners completed the survey (74 poultry, 15 swine, 17 both), which included questions on demographics, flock/herd characteristics, recognition of selected zoonotic diseases and clinical signs in animals, and biosecurity practices for visitors and owners. Most responded that they were aware of avian (92.2%) and swine (84.4%) influenza, and were less aware of other zoonotic diseases such as salmonellosis and brucellosis. The majority of backyard poultry and swine owners combined (62.9%) reported allowing visitors freely around their animals and did not require any special precautions. Backyard poultry and swine owners most commonly reported rarely (32.7%) or never (28.9%) wearing work gloves and never (57.1%) wearing nose/mouth coverings, such as a respirator mask, while handling animals or manure. The study findings indicated that veterinarians (61.5%) and the Internet (50.0%) are the main sources where small‐scale farm producers seek animal disease information. Approximately one‐third (34.9%) of the respondents reported receiving seasonal influenza vaccine. The findings of this study will be utilized to provide targeted veterinary and public health education for the prevention of zoonotic diseases in backyard farm animal settings in Pennsylvania.     

Bioterrorism and equids

A bioterrorism attack can affect the health of many different populations, even those that were not intended as targets. Whether the aim of an attack is humans, animals or crops, the result can be manifested in many species, including equids. Equids comprise a multibillion-dollar industry in the United States, and any disease that affects this trade can have a devastating impact on the economy. In addition, equids could potentially serve as sentinels of an attack against humans, or as amplifying hosts for certain diseases. Knowledge of what diseases have the greatest potential as bioterrorist or agroterrorist agents, how they may present, and what preventive measures are needed to stop their spread is the first step in preparedness. Surveillance for disease outbreaks in equids should be ongoing, with immediate reporting of any unusual findings to the appropriate veterinary and public health authorities.     

在“同一个健康”框架下,加强兽医与人医合作,有效监测和应对人畜共患病和新发传染病

新发传染病主要是人畜共患病,是世界经济和公共健康的沉重负担。这就要求加强检测、鉴别和监视传染病的能力方面投入。高致病禽流感H5N1、新甲型流感("猪流感")H1N1、非典型性肺炎、西尼罗河病毒、地方流行性狂犬病、布鲁氏菌病以及发展中国家暴发的其它人畜共患病及近期猪抗甲氧西林金黄色葡萄球菌,是人类、动物及其环境相互作用的典型范例。面临中国动物和人类常见的新发传染病坚持"同一个健康"战略,这就要求业已存在的兽医和人医及公共卫生机构的通力合作。人的疾病控制系统与动物疾病控制系统虽然都已经建立,但人畜共患病的暴发表明兽医机构和人医机构密切合作的重要性。在保证环境健康的同时,通过动物疾病和人类疾病监测系统的密切合作,中国就一定能够控制人畜共患病。以这种方式进行疾病预防、监测与应对,各层面及各动物生产部门间有效的兽医推广是加强和保持健康生态环境中人和动物健康的有效办法。中国还需大量努力才能达到从制度上保证预防和消灭疾病。透明而准确的人与动物疾病监督通常会产生经济且可持续的预防疾病方法。加拿大在兽医、公共健康、食品安全和人畜共患病预防方面所发挥的作用就是与中国农业部合作,促进必要的、可持续的兽医监督网络的建设。     

A Survey of Canadian Public Health Personnel Regarding Knowledge,Practice and Education of Zoonotic Diseases

Zoonoses, diseases that can spread under natural conditions between humans and other animals, are become a major public health concern in many countries including Canada. In Canada, investigations of zoonotic disease incidents are often conducted by public health inspectors (PHIs). However, little is known about PHIs' knowledge of transmission of zoonotic pathogens, their perceptions of zoonotic disease importance or their education regarding zoonotic diseases. The objective of this study was therefore to assess the knowledge, perceptions and education of Canadian PHIs regarding zoonotic diseases. Data were collected from December 2008–January 2009 using an internet‐based survey distributed to members of the Canadian Institute of Public Health Inspectors national listserv. Responses were received from 229 PHIs in four provinces, with a response rate of approximately 20%. The majority of respondents reported at least 10 years of experience in the public health sector, 80% (181/225) were in frontline positions, and 62% (137/222) were routinely involved in investigations of infectious diseases. Two‐thirds believed that the importance of zoonotic diseases with regards to public health would increase in the next 5 years. Whilst most respondents were able to correctly identify animals capable of directly transmitting common zoonotic pathogens, there were gaps in knowledge, particularly with regard to rabies and transmission of gastrointestinal pathogens by companion animals. PHIs tended to feel that their training on zoonotic diseases prior to working as PHIs was deficient in some areas, or left some room for improvement. Their responses also suggested that there is a need for improvement in both the quantity and the quality of continuing education on zoonotic diseases. In particular, less than one‐third of PHIs received ongoing continuing education regarding zoonotic diseases, and of those that did, nearly two‐thirds rated the quantity and quality as only fair.     

Molecular weapons against agricultural vulnerability and the war on terror

The multiple reports in this issue of the Journal from the Agenda for Action conference, coupled with the analysis by the National Academy of Sciences, the National Research Council, and the Auditor General (UK) on bioterror preparedness and homeland security, highlight the immediate need for rapid disease detection and advanced diagnostic capabilities to protect the public health, animal agriculture, and the numerous associated economies in the United States. In response to the potentially devastating consequences that could arise, there is an acute need for rapid detection of a variety of the lethal foreign animal diseases, such as foot-and-mouth disease virus (FMDV), highly pathogenic strains of avian influenza, classical swine fever, rinderpest, exotic Newcastle disease virus (END), and domestic, vesicular look-alike diseases that include bluetongue, epizootic hemorrhagic disease, vesicular stomatitis, bovine herpes IBR, contagious ecthyma, bovine herpes mammilitis virus, vesicular exanthema, malignant catarrhal fever, and papular stomatitis. Some striking advances are occurring in the creation of rapid technology, including microfluidics, robotics, miniaturization, and biostabilization that are quickly being applied to the development of rapid microbial detection assays. These are now providing important weapons to combat this agricultural vulnerability.     

野鸟传播的重要传染病研究进展

野鸟在迁徙和飞行过程中,因能携带和散播多种病原体,在公共卫生学方面具有重要的意义.通过野鸟能潜在性传播人和动物的重要传染病,包括禽类疫病(禽流感、新城疫、禽痘、禽肺病毒感染、禽分支杆菌感染和鸭瘟)和其他重要疫病(口蹄疫、衣原体病、日本脑炎、莱姆病、西尼罗病毒感染、博尔纳病、Q热、东方马脑炎及致病菌感染),由此应对野鸟传播的疫病予以必要的重视和警惕,并提出有效的防范措施.     

Limited awareness of animal influenza prevention and control among Dai Lue smallholder farmers in Southwest China

Awareness of animal influenza and its prevention and control is important for ensuring livestock health, production and welfare. In China, a country stereotyped as a major source of emerging zoonotic infectious diseases, research on the public understanding of animal influenza is limited to the Han, the main ethnic group. The present qualitative study in Southwest China investigated awareness of animal influenza among the Dai, an ethnic minority. The participants (15 men and 10 women, ages 18–83) were smallholder farmers of pigs and poultry in rural areas of Jinghong, Xishuangbanna, Yunnan Province. A mixture of interviews and group discussions took place in homes and villages. The participants were asked about their knowledge of avian influenza (H7N9), swine influenza (H1N1), precautions taken to protect against influenza, procedures when animals were sick and perceived risk of animal influenza. The data were analysed following coding and thematic analysis. The findings demonstrated a limited understanding of animal health and welfare among participants. Specifically, they were largely unaware of animal influenza (H7N9, H1N1) including its causes, symptoms, prevention and treatment. The farmers were also uninformed of the risks they faced and unknowingly engaged in behaviours which increased direct or indirect exposure to infected animals, a risk factor for human infection. They also reported poor usage of veterinary services. In order to guarantee the health, welfare and production of their livestock, immediate action is needed to enable Dai smallholder farmers to prevent and respond to animal influenza effectively and timely.     

Is salmonellosis still a serious problem in veterinary practice?

Salmonella infections of food animals are of concern to both the food industry and to the public health authorities. Salmonellosis is one of the major zoonotic diseases and its impact on veterinary practice may be judged by a number of criteria. Some of these are examined to determine the extent of the problem.     

Contact Variables for Exposure to Avian Influenza H5N1 Virus at the Human–Animal Interface

Although the highly pathogenic avian influenza H5N1 virus continues to cause infections in both avian and human populations, the specific zoonotic risk factors remain poorly understood. This review summarizes available evidence regarding types of contact associated with transmission of H5N1 virus at the human–animal interface. A systematic search of the published literature revealed five analytical studies and 15 case reports describing avian influenza transmission from animals to humans for further review. Risk factors identified in analytical studies were compared, and World Health Organization‐confirmed cases, identified in case reports, were classified according to type of contact reported using a standardized algorithm. Although cases were primarily associated with direct contact with sick/unexpectedly dead birds, some cases reported only indirect contact with birds or contaminated environments or contact with apparently healthy birds. Specific types of contacts or activities leading to exposure could not be determined from data available in the publications reviewed. These results support previous reports that direct contact with sick birds is not the only means of human exposure to avian influenza H5N1 virus. To target public health measures and disease awareness messaging for reducing the risk of zoonotic infection with avian influenza H5N1 virus, the specific types of contacts and activities leading to transmission need to be further understood. The role of environmental virus persistence, shedding of virus by asymptomatic poultry and disease pathophysiology in different avian species relative to human zoonotic risk, as well as specific modes of zoonotic transmission, should be determined.     

A review of zoonotic disease surveillance supported by the Armed Forces Health Surveillance Center

The Armed Forces Health Surveillance Center (AFHSC), Division of Global Emerging Infections Surveillance and Response System conducts disease surveillance through a global network of US Department of Defense research laboratories and partnerships with foreign ministries of agriculture, health and livestock development in over 90 countries worldwide. In 2010, AFHSC supported zoonosis survey efforts were organized into four main categories: (i) development of field assays for animal disease surveillance during deployments and in resource limited environments, (ii) determining zoonotic disease prevalence in high-contact species which may serve as important reservoirs of diseases and sources of transmission, (iii) surveillance in high-risk human populations which are more likely to become exposed and subsequently infected with zoonotic pathogens and (iv) surveillance at the human-animal interface examining zoonotic disease prevalence and transmission within and between human and animal populations. These efforts have aided in the detection, identification and quantification of the burden of zoonotic diseases such as anthrax, brucellosis, Crimean Congo haemorrhagic fever, dengue fever, Hantaan virus, influenza, Lassa fever, leptospirosis, melioidosis, Q fever, Rift Valley fever, sandfly fever Sicilian virus, sandfly fever Naples virus, tuberculosis and West Nile virus, which are of military and public health importance. Future zoonotic surveillance efforts will seek to develop local capacity for zoonotic surveillance focusing on high risk populations at the human-animal interface.     

A Qualitative Study of State‐Level Zoonotic Disease Surveillance in New England

Zoonotic diseases are infectious diseases transmittable between animals and humans and outbreaks of these diseases in animals can signify that humans are also infected (or vice versa). Thus, communication between animal and human health agencies is critical for surveillance. Understanding how these agencies conduct surveillance and share information is important for the development of successful automated zoonotic monitoring systems. Individual interviews were conducted with 13 professionals who perform animal or human zoonotic disease surveillance in one of the New England states. Questions centred on existing surveillance methods, collaborations between animal and human health agencies, and technological and data needs. The results showed that agencies routinely communicate over suspected zoonotic disease cases, yet there are barriers preventing automated electronic linking of health data of animals and humans. These include technological barriers and barriers due to sensitivity and confidentiality of information. Addressing these will facilitate the development of electronic systems for integrating animal and human zoonotic disease surveillance data.     

The impact of zoonotic diseases transmitted by pets on human health and the economy

In the context of all causes of human morbidity and mortality, or even within the context of all infectious diseases affecting the public health, pet-associated zoonotic infections are of moderate importance. The data documented in Table 1, however, indicate that they do exact significant human health and economic costs. If complete data were available for all of the infections shown in Table 1, the costs would be considerably higher. Moreover, most of these diseases are preventable through educating the public, particularly pet owners, of the zoonotic potential of these diseases, so that they may take precautions to minimize the risks leading to infection. These measures include appropriate health care of pets to eliminate infectious agents, reducing the number of uncontrolled, ownerless pets as well as unwanted or poorly supervised pets, preventing pets from soiling public places with their feces, excluding animals from areas where children play, enforcing leash laws, and promoting responsible pet ownership. Veterinarians, physicians, and public health agencies can aid in these efforts; ultimately, however, the responsibility lies with the pet owner.     

Control of trichinellosis by inspection and farm management practices

The prevention of human trichinellosis by proper meat inspection is a classic example of successful veterinary public health measures. The microscopic methods which have been used for more than a century to test pigs for trichinae were intended to prevent human disease. However, the value of these relatively insensitive direct detection methods, including trichinoscopy and pooled sample digestion, was debated as soon as more sensitive indirect (serological) methods became available. Two issues related to testing were discussed. First, should public health authorities endeavour to prevent all infections of humans rather than simply prevent the occurrence of disease, and second, would epidemiological surveillance and monitoring of the pig population on farms not provide a better control system to prevent human infection. This latter issue is of particular importance for those countries in the world where human trichinellosis acquired from farmed animals is absent and examination of pigs at the abattoir only results in negative findings. In countries where domestic pig infections are virtually non-existent, monitoring of Trichinella infection in wildlife could also contribute to understanding the infection pressure from nature to livestock. Trichinella-free pig farming is a feasible option for controlling this zoonosis, even in endemic areas. This approach provides an opportunity to combine good veterinary practice, in order to prevent animal diseases, with the prevention of Trichinella infection. All animals with access to the environment, or animals which are fed with potentially Trichinella-infected feed (swill, carcasses) will always constitute a public health threat, and must be inspected individually at slaughter (swine, horses, wild boars). Finally, it is important to recognize that trichinellosis is a world-wide problem that needs continuous public health attention. If no control system exists, for whatever reason, the public should be educated not to consume improperly cooked meat.     

浅析畜牧生产中的动物福利与人兽共患病和公共卫生安全

近年来全球因人兽共患病引发的公共卫生事件频繁发生,对世界经济的发展和全球公共卫生安全带来了严峻挑战,此已引起国际社会的高度关注。有专家指出：人类对动物“严酷的剥削与过度的利用”,是造成了人禽（人畜）共患流行性疾病不断暴发的原因。本文阐述了动物福利与畜牧生产的关系和非福利因素对动物生理健康的影响。以期引起全社会关注和促进动物福利事业的发展,积极为畜牧生产中的动物创造一个精神上协调一致、生理上完全健康的生存状态,减少动物疫病（特别是人兽共患病）的发生与流行,保障畜牧业的发展与公共卫生安全。     

Important emerging bacterial zoonotic infections affecting the immunocompromised

The immunocompromised are at particular risk for infection with zoonotic diseases. Persons can be temporarily immunocompromised due to pregnancy or developmental stage (i.e. infants); longer-term or permanent states of immunosuppression can occur as a result of immunosuppressive treatment following cancer or organ transplant, or from infectious diseases, such as AIDS. The focus of this review article is on emerging bacterial zoonotic diseases that are of particular concern among the immunocompromised. Factors that affect disease emergence can include factors such as human demographics and behavior; technology and industry; economic development and land use; international travel and commerce; microbial adaptation and change; and breakdown of public health measures. The immunocompromised need to take precautions when engaging in seemingly normal activities such as food preparation; caring for companion animals; and recreational or occupational activities. The immunocompromised are not only more susceptible to infection, but often suffer more serious sequelae as a result of infection. This review article provides an overview of the major foodborne, respiratory, and vector-borne bacterial pathogens that affect the immunocompromised. The major categories of immunodeficiency are described. In addition, measures that can be taken to prevent infection, including the role of health education, are discussed.