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Monitoring, Control and Education Package to Assist the Egg Industry with Salmonella Reduction and Achieving EU Targets


Recent EU Zoonoses Legislation (Directive 2003/99, Regulation 2160/2003) sets out requirements for monitoring and control of zoonotic organisms, particularly Salmonella and currently a series of National surveys is underway to determine prevalences of Salmonella and to set targets for future improvements. The EU survey for Salmonella in commercial layers has recently been completed and results from this will be used to design monitoring programs for the future in which commercial laying farms will be required to test flocks for Salmonella every 15 weeks during production. A prevalence reduction target will be set and a National control programme must be put in place by each member state and be operational by 2008. By 2009 no eggs from flocks which are infected with S.Enteritidis or S.Typhimurium will be allowed to be sold into the fresh egg market. This will result in considerable economic loss for the industry and may even lead to the slaughter of large numbers of infected flocks on economic grounds. By 2010 the EU target prevalence must be reached and to do this a substantial reduction must be made in the proportion of persistently infected flocks. Previous VLA research has demonstrated how difficult this is to achieve but the impending targets plus approaches to be developed or validated in this proposed project should enable significant progress to be made. <P>

The overall aim of this large multidisciplinary project is to carry out research to fill important gaps in knowledge on Salmonella monitoring and control in the egg industry and to promote understanding of the issues within the industry. <P>

Objective 1 examines the effectiveness of sampling and the specificity in relation to the prevalence in birds. The possibilities for pooling large numbers of samples or large volumes of material and still maintaining a test of validated high sensitivity will also be investigated. <P>
Objective 2 recognises the fact that not all laying flocks where Salmonella is present produce a significant level of infected eggs. 4000 eggs per flock are needed to demonstrate no increased risk compared with the general population of eggs on retail sale. As egg contents are a difficult medium to isolate Salmonella from enhanced methods are required and effective isolation of Salmonella from large egg pools will be investigated with a view to the use of pooled egg culture as a risk management tool for prioritising immediate action to be taken when Salmonella is identified in laying flocks. <P>
Objective 3 considers proper delivery of live vaccines. To provide the best possible protection vaccine in sufficient dose must be delivered rapidly, before the viability declines, to the vast majority of the flock. The work proposed in this objective will investigate in detail the causes of failure to administer live vaccine effectively. This will involve investigative visits by VLA veterinarians in conjunction with technical staff from the relevant vaccine manufacturers. <P>

Work in VLA/University of Bristol Project OZ0321 has shown that commercial laying birds and mice can be most easily infected by contact with contaminated drinking water. Infection by this route in laying birds does not appear to be reduced in birds vaccinated with live vaccine. There are no independent studies of how the currently available live and killed vaccines compare in terms of prevention of infection when birds are placed in cages where there is residual contamination. The work in Objective 4 will provide information on the relative efficiency of the vaccines under controlled conditions and in the field. <P>

Objective 5 will investigate methods of improving the response to vaccination by mucosal delivery, additional doses and combination with competitive exclusion. This will be a combination of controlled laboratory studies and field investigations. This objective will also provide an opportunity for a pilot investigation of phage therapy for reducing Salmonella in infected birds. <P>
Objective 6 is an important package of work as it addresses the root causes of current industry Salmonella problems: environmental contamination and wildlife infection on multiple age layer farms. A multidisciplinary team of veterinary microbiologists, epidemiologists, and experts on rodent control and pest control from VLA, RDS and CSL will be engaged in farm investigations to design effective methods for producers to audit hygiene and cleaning and disinfection standards, as well as populations of potential Salmonella vectors. This will provide a blueprint for Salmonella control. <P>

Objective 7 considers the cost implications of the proposed EU Salmonella legislation, specifically the requirement to exclude eggs infected with Salmonella Enteritidis and S.Typhimurium from the fresh market, and the cost/benefit control measures. As large cage laying flocks are most at risk from Salmonella infection the cost implications of this are potentially very large and may lead to financial collapse and slaughter of flocks. This analysis will therefore assist industry with decisions on action for individual farms as well as whole industry initiatives. <P>
Objective 8 is a knowledge transfer package which aims to distill all current and new knowledge of Salmonella control from the experience of the project team and industry consultants as well as new knowledge from the project and other published and unpublished material. The aim will be to design and pilot a ‘roadshow’ package, based on the successful Food Standards Agency ‘Campylobacter’ campaign, and to produce an educational DVD and e-mail information network. <P>

This package of objectives therefore fully supports industry priorities and public health priorities and will provide industry with effective methods to meet and exceed future EU requirements leading to continual and ongoing improvements in the Salmonella status of the National laying flock.

Veterinary Laboratories Agency, UK
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