ACT3開催レポート

疫学から食の安全と健康を考える国際シンポジウム開催

【3月28日(火)/東京大学農学部 1号館8番教室】
アグリコクーン食の安全・安心フォーラムグループ主催、日仏国際シンポジウムが開催されました。 食の安全と健全の確保に向けた疫学の展開をテーマに、日仏のBSE対策、口蹄疫・狂犬病予測モデルと対策などの研究発表が行われました。 報道等で注目されている話題でもあり発表者への質疑応答も活発に行われました。 ご来場いただいた皆様、ありがとうございました。(ご来場約80名) ※タイトルをクリックすると各講演の要旨(英文)をご覧頂けます。
座長:吉川泰弘 (東京大学大学院農学生命科学研究科)
13:00-13:30 国際獣疫事務局(OIE)の活動について
藤田陽偉 (国際獣疫事務局大平洋地域事務所)
要旨
国際獣疫事務局(OIE)の活動について
Activities of the World Organization for Animal Health (OIE)

藤田 陽偉(国際獣疫事務局太平洋地域事務所)
Teruhide Fujita, OIE Regional Representative for Asia and the Pacific


Animal health improvement is one of the most critical areas for the development of the livestock agricultural sector in increasing livestock productivity, minimizing losses caused by diseases, reducing threats and risks to humans and for smooth and safe international trade in animals and animal products as well as food security and poverty reduction.
The World Organisation for Animal Health (OIE; Office International des Epizooties) was established in Paris, France in 1924 by the then 28 signatory countries; now the number of Member Countries increased up to 167 with the internationally significant recognition of its important roles by the countries worldwide.
The OIE has functioned as an intergovernmental organization for the broader areas of animal health improvement, and prevention and control of animal diseases including zoonoses, with such major objectives as (1) ensuring transparency in the global animal disease situation, (2) collecting, analyzing and disseminating scientific veterinary information, (3) contributing expertise and encouraging international solidarity in the control of animal diseases, (4) safeguarding the international trade by publishing health standards for trade in animals and animal products within its mandate under the WTO SPS Agreement, (5) improving a legal framework and resources of National Veterinary Services, and (6) providing a better guarantee of the safety of food of animal origin and promoting animal welfare through a science-based approach.
The OIE develops normative documents of the international standards relating to the rules that Member Countries can use to protect themselves from the introduction of diseases and pathogens. Those international standards include the Terrestrial Animal Health Code and the Aquatic Animal Health Code which are the reference documents assisting Member Countries in establishing their health regulations in, and the Manual of Diagnostic Tests and Vaccines for Terrestrial Animals and the Manual of Diagnostic Tests for Aquatic Animals which include the internationally agreed laboratory methods, and other Recommendations relevant to animal health.
Such activities of the OIE have been strongly supported by its Member Countries, the OIE Specialist Commissions and the OIE designated World Reference Laboratories as well as the OIE Collaborating Centres. The Organization has kept close working linkages with many other international and regional organizations.
The OIE has now its Regional Representations in the 5 regions. The OIE Regional Representation for Asia and the Pacific was established in Tokyo, Japan (OIE Tokyo), as the first Regional Representation of the OIE.
The major priority and challenging areas of OIE Tokyo consist of (1) strengthening regional alliance and networks on animal health, prevention and control of animal diseases, (2) capacity building of National Veterinary Services, and (3) development of regional animal health policies and strategies.
OIE Tokyo has recently expanded its activities of animal health improvement to further work with the Member Countries in Asia and the Pacific in coping with the current situation of animal diseases including occurrences of Emerging Diseases. It is considered for example that the Permanent Secretariat of the Regional Steering Committee for the FAO/OIE initiative Global Framework for progressive control of Transboundary Animal Diseases (GF-TADs) will be a strong supporting mechanism to tackle such diseases as Foot and Mouth Disease, Highly Pathogenic Avian Influenza and Classical Swine Fever in Asia and the Pacific.
13:30-14:20我が国の飼育犬に狂犬病が侵入した場合の伝播と流行拡大の数理モデルによる解析
大日康史(国立感染症研究所)・ 井上智(国立感染症研究所)
要旨
我が国の飼育犬に狂犬病が侵入した場合の伝播と流行拡大の数理モデルによる解析
A Mathematical Model for Rabies to Evaluate Control Measures

大日 康史(国立感染症研究所) ・ 井上 智(国立感染症研究所)
Yasushi Ohkusa,Ph.D., National Institute of Infectious Disease, Infectious Disease Surveillance Center
Satoshi Inoue, D.V.M., Ph.D., National Institute of Infectious Disease, Department of Veterinary Science


Objective: We propose a mathematical model for rabies which describes how rabies prevails among accompanied dogs when the infected dogs are introduced. Moreover, we show its usefulness to evaluate the counter measure with which to contain it.
Method: We used a type of mathematical model called individual based model (ibm), which can describe the behavior of individual agents, i.e. accompanied dogs in this model, and the development of rabies. We assume that there are no ownerless dogs before the outbreak, the natural history of rabies is borrowed from the existing literature, and accompanied dogs are located every 100m in the area of 100km2. We suppose that a quarantine order and the hunting of ownerless dogs are potential counter measures after an outbreak. Four important parameters are examined: immunization rate before outbreak, timeliness of detection of rabies, compliance to quarantine order, and efficacy of the hunting of ownerless dogs. The detection timing of a rabid dog is defined by the number of deceased rabid dogs before the recognition of the introduction of rabies.
Result: If the immunization rate is low and recognition of the infected dog is delayed, the cumulative number of infected dogs is significantly higher. On the other hand, when the immunization rate is more than 70%, it can shorten the time it takes to contain the outbreak, but this effect is not significant.
Conclusion: We proposed a mathematical model of rabies prevailing among accompanied dogs. This model was usefulness to evaluate the counter measure against rabies. However, we need more examination to revise its structure and parameter setting through detail communication with veterinarians and public health authorities. Moreover, we want to improve this program so that veterinarians and public health workers can use it easily and useful to evaluate the counter measure against rabies.
14:20-15:10口蹄疫の疫学分析とリスク評価
筒井俊之 (動物衛生研究所)
要旨
口蹄疫の疫学分析とリスク評価
Epidemiological Analysis and Risk Assessment of FMD

筒井 俊之(動物衛生研究所)
Toshiyuki Tsutsui, National Institute of Animal Health


Foot-and-mouth disease (FMD ) is a highly contagious animal disease caused by FMD virus. This disease affects cloven-hoofed animals including main domestic livestock, such as cattle, pig, sheep and goat. FMD has a great potential to bring about huge economic losses in a livestock industry due to its high contagiousness. In addition, the presence of FMD often restricts the international trade of animals and animal products.
Because FMD has been identified as an infectious disease affecting livestock farming since more than 100 years ago, a lot of researches have been conducted on its etiology, immunology and epidemiology. These intensive researches have largely contributed to understanding the nature of FMD. However, this disease still affects livestock production in many countries in Africa, Asia and South America. In addition, FMD often invades previously free countries or regions where succeeded in the eradication. The recent entry to the UK caused devastating damages on the livestock industries, as well as other related industries. Many FMD free countries have stringent measures to prevent the disease from the introduction into their territory, and prepare for immediate eradication.
In order to establish the preventive and control measures against this disease, the epidemiological analysis and risk assessment play important roles. It is known that epidemiological modeling studies contributed to the consideration of control strategies during the UK epidemic. Qualitative risk assessment is widely used for deciding border control measures to prevent the introduction of FMD through the import of animal and animal products.
The epidemiological analysis is a term containing broad meanings and used without clear definition in general. On the other hand, risk assessment is clearly defined by international organization like OIE, as one of the components in risk analysis. The risk assessment can be described as “the evaluation of the likelihood of the occurrence and the likely magnitude of the consequences of an adverse event to animal or human health”, referring to the OIE guideline. As this definition describes, the risk assessment is applied for considering preventive measures against a possible adverse event, while epidemiological analysis is also used to analyze actual disease outbreaks for understanding the spread of diseases, the risk factors of infection, the efficacy of control measures and so on. In this presentation, I assumed the epidemiological analysis as an approach to study epidemiological aspects of the disease for the purpose of the disease control, although it cannot be completely separated from risk assessment. As an example of this analysis, I show our study on the evaluation of the surveillance conducted against FMD in Kyusyu in 2000. In this study, we quantitatively evaluated the efficacy of surveillance using a stochastic modeling technique. We also considered the factors affecting the efficacy of the FMD surveillance in an outbreak area. The one of key measure for the containment of FMD is to set a movement control area around an outbreak site. We have conducted another pilot study to analyze movements, which potentially spread the disease.
As for the import risk assessment, the OIE guideline divided it into four components, namely release assessments, exposure assessments, consequence assessments and risk estimation. In general, the risk assessment is conducted on the component basis, and often focuses on one or two components for answering a specific question on the risk. As an example, I show a qualitative import risk assessment on FMD, which focused on the release assessment part.
In general, there are two types of approach in both epidemiological analysis and risk assessment. One is a qualitative approach based on descriptive analysis. The other is a quantitative approach, which uses numerical values to describe the magnitude of effects. Both approaches are valid, but need to be used on the case-by-case basis considering their advantages and disadvantages.
15:10-15:30休憩
座長:小野寺 節 (東京大学大学院農学生命科学研究科)
15:30-16:30 フランスにおけるフードチェーンのBSE汚染防止政策
Sylvain Lehmann (Institut de Genetique Humaine du CNRS)
要旨
フランスにおけるフードチェーンのBSE汚染防止政策
Prion Infected Cell Culture Models for Basic and Applied TSE Research; Overview of the French Policy for the Prevention of Food Chain Contamination by Bovine Spongiform Encephalopathy.

Sylvain Lehmann, Institut de Genetique Humaine du CNRS


Prion infected cell cultures which are developed for decades represent relevant experimental models to study prion diseases. They indeed allow to study the cell biology of the prion protein, they represent valuable tools to evaluate therapeutic agents and to analyze the molecular determinants of prion susceptibility, replication and toxicity. They could represent also an useful alternative to animal bioassays for the detection of prion infectivity. We will illustrate these properties through several examples.
One important limit of actual cell culture models is their limitation to few prion strains and species. There is therefore an urgent need to develop new models susceptible in particular to BSE and human prions. We will report a current program of the laboratory towards this goal using neural stem cells, as a new model for cell culture studies of infectious prions.
Finally, as a vice president of the French expert committee on TSE (from the French Agency for Food Safety, Afssa) we will give an overview of the French and European policy for the prevention of food chain contamination by BSE.
16:30-17:20 日本におけるBSE検査の食品衛生への影響の評価
春日文子(国立医薬品食品衛生研究所)・ 筒井俊之(動物衛生研究所)
要旨
日本におけるBSE検査の食品衛生への影響の評価
Assessment of the Impact of Cattle Testing for BSE on Food Safety in Japan

春日 文子(日本医薬品食品衛生研究所) ・ 筒井 俊之(動物衛生研究所)
Fumiko Kasuga, National Institute of Health Science
Toshiyuki Tsutsui, National Institute of Animal Health


Microbiological risk assessment for food safety is a logical analyzing procedure into the events involved in food supply system. It is composed of Hazard Identification, Exposure Assessment, Hazard Characterization, and Risk Characterization, though full components are not always required depending on the questions from risk managers. Epidemiology contributes to the prioritizing and selecting risk assessment targets, providing input data for risk assessment models, and validating results of risk assessments as well as presenting baseline data for setting public health goals in risk management. This presentation demonstrates an example of Exposure Assessment to evaluate the impact of cattle testing strategies for bovine spongiform encephalopathy (BSE) on the human consumption of infective prion in Japan.
Since the first case of BSE was detected in 2001 in Japan, screening tests for BSE have been applied to all cattle at slaughterhouses both for surveillance purposes and as a meat safety measure. We quantitatively evaluated the influence of removing specified risk materials (SRM) and the alternation of age limits for testing cattle at the slaughterhouse on human exposure to the BSE agent, upon hypothetical risk managers’ questions. A stochastic model using Monte-Carlo simulation was constructed, and BSE infectivity entering the food chain from a single BSE-infected animal at slaughter was estimated. Input variables used for the model were mainly obtained from published reports including epidemiological data from the Cattle Identification System, but some were assumed based on other available information and estimates. Murine intra-cerebral ID50 (m.i.c.ID50) units were used as units for BSE infectivity in order to reduce uncertainties related to species barriers. Removal of SRM effectively reduced the BSE agent destined for human consumption. Cattle screening tests further reduced the infectivity, but reduction efficacy did not differ much among the testing strategies with various age limits for the test. Sensitivity analyses indicated that the characteristics of BSE infectivity accumulation during the incubation period, extension of the incubation period, and lowering the detection limit of screening tests did not have significant impacts on relative infectivity reduction, which remained stable irrespective of testing strategy or changes in these parameters. The results suggest that the impact of changing the age limit for testing cattle in Japan on beef safety is small, provided that the removal of risk materials is conducted properly. This study also shows that a targeted approach of microbiological risk assessment is possible to provide limited but meaningful outputs to specified risk management questions.