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Zawartość zarchiwizowana w dniu 2022-12-23

Foodborne Zoonoses: a Coordinated Food Chain Approach

Cel

A. BACKGROUND

Microbiological food safety in Europe and the rest of the developed world is assessed in terms of acceptable levels of risk of humans contracting food-related illnesses. For certain pathogens such as Verocytotoxigenic Escherichia coli (VTEC) the acceptable level of risk may be as low as zero. Our food-supply chains whether international, national or local provide numerous opportunities from farm to fork for the contamination of food and water for human consumption.

Given the enormous number and variety of potential contamination sources along the food processing chain, it is unrealistic to imagine that all food can be kept free from contamination throughout the process. However, it is now recognised that the most appropriate way to enhance food safety is to identify the critical contamination points affecting the safety of the final product. It should then be possible to introduce the most effective measures to minimise or eliminate the possibility of contamination from food production and processing to distribution, preparation and consumption. Advances in the twentieth century such as pasteurisation, refrigeration and more recent improvements in hazard analysis and control
along the foodchain have contributed to improvements to the microbiological safety of most foods. Nevertheless, foodborne disease remains a significant cause of morbidity and mortality in Europe and the rest of the developed world. A recent national surveillance study

in England and Wales revealed that one in five people developed infectious intestinal disease each year, and that Campylobacter and Salmonella were the most common bacterial pathogens isolated (1). In the United States it has been estimated that foodborne diseases may cause up to 76 million illnesses, 325 000 hospitalisations, and 1 800 deaths each year (2). In the same study Campylobacter, nontyphoidal Salmonella and VTEC accounted for the vast majority of bacterial foodborne disease requiring hospitalisation. Toxoplasma gondii and Norwalk-like viruses accounted for the great majority of severe cases of parasitic and viral infections respectively. These two recent studies bear out the generally high estimated national and international human incidence of foodborne pathogens, especially Salmonella and Campylobacter in most parts of the developed world .

Taken together this data confirms the continuing importance of food as a source of human illness and, in particular, of foodborne zoonotic diseases arising from the infection of farmed livestock throughout Europe with these microbial pathogens.

Estimates for economic loss covering health costs, lost production and family-related expenses are imprecise due to the paucity and non-standardisation of data and approaches to provide the estimates. However, in England and Wales Salmonella cases alone could cost in excess of £100 million each year and in the US in 1996 it has been estimated that Campylobacter spp., Salmonella, VTEC O157 and T. gondii cost the public purse 0.8-5.7; 0.9-3.6; 0.16-0.3 and $3.3 billion respectively (8).

As surveillance systems and epidemiological tools have developed and improved, increasing numbers of foods, and in a number of cases the source of contamination, can be traced and linked to major food poisoning outbreaks. For example, S. enteritidis in poultry and in particular egg products, Campylobacter in poultry meat products, and E. coli O157 in ground and sliced beef and contaminated dairy produce. Many of these outbreaks could have been avoided through correct hygiene procedures in the handling of foods. However, only a coordinated farm to fork approach is likely to achieve permanent and significant reductions in foodborne infections in the future. Countries in the European Union operate within the framework of the 1992 Zoonoses Directive 92/117/EEC to monitor and control Salmonella in poultry flocks (9). The strategy focuses on the poultry breeding and layer sector and has, to a greater or lesser extent, demonstrated that an integrated and coordinated approach to
controlling Salmonella in domestic livestock is feasible and leads to a sustained reduction in human incidences. This is best exemplified by examining the relative effectiveness of the Danish control programmes via the published estimated food sources of human salmonellosis in Denmark 1988-1998 (Fig. 1)(10).


Although admitted to be a rather crude assessment it clearly shows the dynamics in the changing sources of human salmonellosis over a 10-year cycle. Denmark experienced three waves of human salmonellosis, where the majority of cases were attributed to three different food sources. In the late 1980s broilers were the major food source, whereas in the mid 1990s pork products increased in significance and from the mid 1990s to the end of the century eggs and egg products predominated. At each of the peaks of human salmonellosis new control programmes in animals were implemented and resulted in a reduction of human cases attributable to that particular food source. This is the clearest evidence to date that intensive and coordinated Salmonella control programmes in animals can effect a reduction in human salmonellosis from that food source. It also provides sound evidence that controlling foodborne pathogens in animals is a very important control point in the entire foodchain.

However, some successes in reducing Salmonella infections should not detract from other real challenges for the future. Campylobacter infections are now the commonest cause of bacterial foodborne infections and in a recent study in the UK, ranked second in the list of organisms isolated from cases of infective diarrhoeal infections. Human VTEC O157 cases have continued, implicating a variety of contaminated food sources and direct animal to human contact. Cryptosporidium continues to cause large outbreaks through contamination of the water supplies. Increase and emergence of antibiotic resistance and multiply resistant bacterial strains, some of which have arisen from animals and their environment, highlights the immediate requirements for improved surveillance methods and alternative strategies for controlling infections. Emergence of new Salmonella epidemic strains e.g. S. typhimurium DT104 and continued evolution of VTECs highlights the need for robust early-warning systems and greater understanding of the mechanisms of genetic mutation and adaptation (11).

The farm to fork concept has encouraged closer cooperation between all sectors of the food industry and as stated above achieved some considerable successes in reducing Salmonella in livestock. However, it is likely that the most cost effective way within limited resources in targeting longer term strategies to control foodborne zoonotic infections in animals, is to focus on emerging trends in human infections caused by the major foodborne zoonotic pathogens, since most of these organisms are asymptomatic in animals. Thus integrated research and surveillance of animal and human foodborne zoonotic infections is crucial to future strategies. For example, rapid dissemination of changing trends between veterinary and medical sectors to improve response to emerging pathogens, changes in antimicrobial resistance patterns, coordination of surveillance systems that can accurately identify results of intervention methods implemented along the food chain and coordination and integration of research objectives. Thus the original farm to fork approach often ignored the key component along the food chain which should help to formulate future strategies i.e. seamless and coordinated foodchain strategy. It is also now recognised that many of the most effective solutions will not be pathogen specific but focus on factors common to many different organisms in the foodchain. At present there are some Europe-wide initiatives such as CAMPYNET for the harmonisation of subtyping schemes for campylobacter, a Concerted Action project on VTEC and an EC research project on risk assessment on Cryptosporidium parvum. COST Action funding is a very efficient means of linking research and surveillance activities across Europe. In particular, by drawing together specific pathogen-based information from various European and national initiatives this COST Action will facilitate real generic discussions and studies in the control of foodborne zoonoses. Thus, this COST Action seeks to complement and build upon COST Action 97 (Pathogenic Microorganisms in Poultry and Poultry Products) to cover the major livestock species and to include all stakeholders along the foodchain. This will provide a framework for the rapid transfer and

dissemination of information between veterinary, food and medical sectors; opportunity to
develop generic, integrated research and surveillance proposals through future EC proposals; exchange of workers between key veterinary and medical organisations and to develop new relationships across Europe. These activities will be addressed in the various activities described below.

B. OBJECTIVES AND BENEFITS

The main objective of the Action is to better control foodborne zoonotic infections.

This will be achieved by focusing on four key secondary objectives that are closely inter-linked and will be implemented through Working Groups (WG). Firstly, there will be continued emphasis on the development and harmonisation of diagnostic and typing methods. Meeting this objective is crucial to the inter-comparability of surveillance data along the foodchain and between countries and regions in Europe. Progress has been made in areas such as Salmonella and VTEC O157 detection but much more effort is needed, in particular, to harmonise molecular typing techniques and methods for measuring antimicrobial resistance. Secondly, the emergence of new foodborne pathogens such as VTEC (O157 & non O157), pandemic S. typhimurium DT104 strain and multi-resistant organisms highlight the need to provide early warning or alert surveillance systems for potential emerging pathogens. The development of Salmnet and Enternet are contributing to developments. However, they need to be developed throughout Europe and along the whole foodchain so that changing trends of foodborne pathogens anywhere along the processing chain can be identified and the information disseminated to the rest of Europe. Thirdly, by applying a quantitative risk assessment to the foodchain, critical intervention points and areas requiring further surveillance and/or research can be identified and contribute to improved cost-effective control programmes that also offer new opportunities to countries in which

control methods have hitherto been considered too expensive. Lastly, a greater understanding of the mechanisms of survival of zoonotic pathogens along the foodchain will aid risk assessment. For example, techniques are now emerging whereby one can link the identification of the hazard (potential pathogen) with a detailed molecular profile of the organism including presence or absence of key survival and virulence genes. This has tremendous potential in the application of likely risk associated with the isolation of new pathogens along the foodchain.

C. SCIENTIFIC PROGRAMME

The scientific programme focuses around working groups:

Working group 1. Harmonisation of diagnostic and typing methods.

The task of this group will be to improve the standardisation and comparability of diagnostic and typing methods for the major zoonotic foodborne pathogens encountered in Europe

Key objectives of the WG will be:

(a) To review current diagnostic and typing methods used in Europe.
(b) To prioritise methods for improved harmonisation.
(c) To provide a focus for dissemination of inter-comparability ring trials.
(d) To facilitate standardisation and quality across Europe through training and exchange of methods.

The expected benefits will be improved standardisation and comparability of surveillance data across Europe.

Working Group 2. New and emerging foodborne pathogens

The task of this group will be to augment existing frameworks in Europe such as the Enternet system for human bacterial pathogens to provide a comprehensive early warning process for the rapid dissemination of information on new and emerging foodborne pathogens.

The main objectives of this WG will be:

(a) To instigate a network within Europe to rapidly transmit details of rare and unusual foodborne pathogens.
(b) To provide opportunity to present detailed case definitions to other partners.
(c) To rapidly exchange strains to aid research and surveillance.

The expected benefits will be a more proactive approach to the identification of new and emerging foodborne zoonoses.

Working Group 3. Quantitative foodchain risk assessment

The task of this group will be to coordinate the development of quantitative foodchain risk assessments based on agreed priorities and inform other WGs on the outcomes and actions arising from these assessments.

The main objectives of this WG will be:

(a) To review currently available foodchain risk assessments carried out in Europe and elsewhere.
(b) To identify priority areas for formal quantitative risk assessments.
(c) To facilitate discussion of risk assessments carried out in Europe.
(d) To inform other WGs on the outcomes of these risk assessments so as to inform future surveillance and research priorities.

The expected benefits will be the continued integration of risk assessment into research, surveillance and policy initiatives.

Working Group 4. The Survival of zoonotic pathogens through the foodchain.

The aim of this group will be to gather all available knowledge on the molecular and phenotypic profiles of the major pathogens with special emphasis on those genes implicated in the virulence and survival of the organism through the foodchain.

The main objectives of this WG will be:

(a) To review current knowledge of virulence and survival genes in foodborne pathogens.
(b) To facilitate presentation of novel research findings.
(c) To seek to apply genomic chip technology to specified pathogens.
(d) To facilitate exchange of techniques and staff through short-term scientific missions.
(e) To regularly update other WGs on any new findings.

Expected benefits will be the integration of hazard and risk and a greater understanding of the likely human and animal importance of new and emerging strains arising in the foodchain.

D. ORGANISATION, TIMETABLE AND DISSEMINATION

The organisation and coordination of the COST Action will be assumed by a Management Committee (MC). Ideally, members from each participating country will represent the whole foodchain from farm to fork. At the first meeting the MC will established the general frameworks and remit of the WGs.

In each WG, workshops (2-3 days) will be organised at least annually in one of the participating countries and the proceedings will be published. Scientific exchanges will be considered throughout the year and recommendations transmitted to the MC by the WG Chair. Reports of the scientific exchanges will be presented at the workshops. The MC will hold an annual management meeting to review progress. Consideration by the MC will be given to the production and maintenance of an Action Web Site to facilitate the dissemination of information about the Action.

One of the most important outcomes of this Action is to facilitate sustainable and new collaborative networks in the field of foodborne zoonoses and to apply these to improve the coordination of research and surveillance activities across Europe, through much closer cooperation between the veterinary, food and medical sectors. This is particularly relevant to generic solutions to control foodborne zoonoses. Thus, to help achieve and assess progress the duration of the COST Action should be five years. During this period it is envisaged that the COST Action will combine with at least three International meetings. One such meeting could be the International meeting on Salmonella to be held in Ploufragan, France in 2002.

There will also be at least two workshops representing all the WGs most likely at the beginning and end of the Action. External experts from outside COST member states will be invited to participate in several meetings. Industry will also be encouraged to participate fully in all the WGs.

Dissemination of achievements will be either by using the OPOCE publication scheme or through publication with renowned publishers. A web site will be developed for fast dissemination of intermediate information and results to participants and other stake holders. A person from the MC will be appointed to develop the website and to coordinate the dissemination of data. Besides the periodic dissemination via the internet, a final report will be written, including an executive summary, final financial statement, and a summary of the results achieved in comparison to initial and updated COST-action plans. Identified stakeholders including potentially interested enterprises and policy makers will be specifically informed about the Action. They will be asked to attend, if appropriate. Dissemination of specific technical knowledge between scientists will be further stimulated by short term scientific missions.

E. ECONOMIC DIMENSION

The following COST countries have actively participated in the preparation of the Action or otherwise indicated their interest:

Belgium, Czech Republic, Denmark, France, Germany, Hungary, Ireland, Italy, the Netherlands, Spain, Sweden, the United Kingdom.

A number of international bodies and industrial companies will also be interested and support the Action in some form.

On the basis of national estimates provided by the representatives of 12 of these countries the overall cost of the activities to be carried out under the Action has been estimated, at 2000 prices, at roughly EUR 30 million.

This estimate is valid under the assumption that 12 of the countries mentioned above, but no other countries, will participate in the Action. Any departure from this will change the total cost accordingly.

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