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Australian Egg Farms Meeting Challenge of Salmonella

02 July 2015

Eliminating Salmonella on egg farms is impossible, so the risk to human health needs to be thoroughly managed and controlled.

According to Kylie Hewson from the Australian Egg Corporation the presence of Salmonella enterica serovars (particularly some Typhimurium serotypes), which can cause salmonellosis in humans, throughout the supply chain has become an enduring challenge for the egg industry and has caused major issues for the sector’s reputation.

Speaking at the 26th annual Australian Poultry Science Symposium in Sydney earlier this year, Ms Hewson said that the presence and spread of Salmonella depends on numerous variables, and as such, there is no single effective control measure.

Therefore, she said, the presence and control of Salmonella are complex issues that are subject to a combination of both real and perceived risks.

There is an abundance of peer-reviewed and grey-literature regarding many aspects of Salmonella, however, the type and availability of this information varies within egg production and consultancy companies.

The phrases “everything is known and we don’t need to fund more work” or “we did this work 30 years ago” are heard often during industry meetings to discuss Salmonella project proposals, she said.

“Yet the challenge of Salmonella remains on-farm and in the market place,” said Ms Hewson.

“Therefore, there is an obvious need to collate readily available information and make it more accessible to the entire industry to provide a framework for the application of knowledge.

“Currently, the level of understanding of the issue (i.e. the cause as well as the effectiveness of various controls) is variable within industry, government regulators, the food service sector, and the consumer community.

“Recent R, D&E activity and literature reviews in preparation by the AECL Council for Sustainable Egg Farming (CSEF) are expected to provide a robust body of knowledge and a clear description of the risks and possible management options of egg related salmonellosis illness in Australia.”

As elimination of Salmonella on egg farms is impossible, the risk of human illness needs to be appropriately managed.

However, as this is a technically complex issue with varying risks (and varying understandings of these risks) between on-farm and in food service, an effective management strategy will need to be a collaborative effort that relies on the development of good relationships between industry and government agents/regulators, founded on robust information and involve a system (or systems) to control highest risk Salmonella enterica serovars at various stages in the supply chain.

Ms Hewson said that key stakeholders, including state regulators/health departments, industry associations, egg producers, researchers and technical consultants (including veterinarians) are involved in the process with the aim to build relationships and guide programme development.

Coordination, review and dissemination of comprehensive, yet coherent, information regarding Salmonella is currently underway in Australia with the aim to draft a risk management plan for the control of Salmonella through the entire egg supply chain.

Ms Hewson said that this management plan needs to be robust and measurable (i.e. it relies on data and can be audited if required), able to be updated easily to include new information as it becomes available and also include options for industry uptake and development.

Outcomes will also include the development of training materials and control documents for various stages of the supply chain which focus on key issues and support a management programme that is both applicable to, and comprehensible by, regulators and producers.

In research sponsored by Australian Egg Corporation Limited Vivek Pande, a recipient of an International Postgraduate Research Scholarship, and others showed that birds infected with Salmonella are still shedding the pathogen five weeks after infection.

The research findings regarding the intermittent and prolong shedding of Salmonella agreed with other research into the problem, conducted by Lister and Barrow (2008) and Gole et al. (2014).

In the Australian study, Mr Pande said: “Egg or egg product related Salmonella poisoning is a major concern for the egg industry.

Salmonella typhimurium (S. typhimurium) is the most frequently reported serovar in egg related food poisoning outbreaks in Australia (The OzFoodNet Working Group, 2013).

“It has been studied that Salmonella serovars such as Enteritidis has the capacity to contaminate developing eggs within the oviduct; however the vertical transmission ability of Australian S. typhimurium strains has not been investigated.

“Older birds are also considerably more resistant to Salmonellae than are young chicks.

“Shedding of Salmonellae in chicken faeces can be intermittent and may continue for many months.”

He said that persistence of S. typhimurium DT 9 in the poultry shed environment could cause egg shell contamination.

However, a further study that was also reported at the symposium in Sydney, showed that different pore structures, the total number of pores and the shell thickness, did not make a difference to the penetration of Salmonella into the eggs.

The research, An Examination of Eggshell Pore Structure and Penetration by Salmonella typhimurium by A. Ray, J. Roberts, K. Chousalkar and R. Flavel, conducted within the Poultry CRC, established and supported under the Australian Government's Cooperative Research Centres Program, found that no significant differences in the incidence of types of pore structure or Computed Tomography measured shell thicknesses were found in penetrated and non-penetrated shell samples. All measures were very similar except for the number of internally branching pores.

July 2015



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