Capitalising on the zero Salmonella ruling in table eggs
by A.C. Berge, and Z. Kay,
published in World Poultry, 2010, Vol 26, No 10, pp.36-37

Introduction

Egg producers in the European Union are currently facing a number of challenges; including the cage ban and eliminating Salmonella from flocks. Whilst these challenges may have positive benefits for bird welfare and public health, they also result in additional costs for producers. Although the ultimate goal of the Salmonella control programme is to decrease the threat to humans of Salmonella in eggs, producers can also use the programme to increase animal health and productivity – giving a market advantage.

The Public Health consequences of Salmonella in layers

Public health risks of Salmonella infection in laying hens are mainly associated with exposure to contaminated eggs. Two Salmonella serovars (Enteritidis and Typhimurium) account for around 80% of all diagnosed human cases. The majority of Enteritidis cases are believed to be caused by eggs and poultry meat. The importance of Enteritidis in egg production is largely due to its ability to persist in the reproductive organs, resulting in internally contaminated eggs, as well as egg shell contamination. 

The number of diagnosed cases in relation to the number of true cases of Salmonella varies widely between countries and under-reporting is recognised world-wide. In the European Union, with a human population of 500 million there were approximately 130,000 verified salmonellosis cases in 2008. This could translate into 1 to 15 million human salmonellosis cases per year. The costs of salmonellosis in the Netherlands was estimated at 11 million € per year (Haagsma, 2009). Extrapolating this to the whole EU would result in a total costs between 0.2 and 3 billion € per year (EFSA 2010). The reported incidence of human salmonellosis has decreased in the EU over the last four years, largely due to a reduced number of Salmonella infected layer flocks and subsequently less Salmonella in eggs.

A study in EU countries (2004-2005) found a range of Salmonella positive flocks varying between 0% and 79% (EFSA, 2007). In the EU, on average, 20% of all farms were positive for Enteritidis and/or Typhimurium. Salmonella control programmes in laying hens have been effective in reducing the prevalence of human Enteritidis cases. In Denmark the percentage infected layer flocks was reduced from 13.4% in 1998 to 0.4% in 2006 and during this period a parallel decrease was seen in human salmonellosis (Korsgaard, 2009). After Salmonella vaccination in 2004 in Belgium, laboratory confirmed cases of human salmonellosis dropped from 12,894 in 2003 (89% due to Enteritidis) to 3,831 in 2008 (Collard, 2008). A recent study by the European Food Safety Agency indicates that major reductions in human salmonellosis in the EU can be achieved by reducing Salmonella in layers (EFSA 2010).

European Union Legislation

In 1992, an EU directive 92/117/EEC started the Salmonella control programme by requiring Salmonella control in breeding poultry.  Regulation 2160/2003 expanded Salmonella controls to production poultry including layers, and specifically laid down plans for reduction of Enteritidis and Typhimurium. Regulation 1168/2006 sets a target for annual reduction of Salmonella positive layer flocks until 2% or less flocks remaining positive.

Salmonella Control

The layer industry has already demonstrated that with an integrated holistic approach Salmonella contamination of eggs can be significantly reduced. The bases for successful control of Salmonella are good farming and hygienic practices. The costs of implementing these measures totally depend on the structure of the farm. However, there are major components of Salmonella control that are applicable to all producers. Day-old chicks should be sourced from Salmonella-free breeding flocks and hatcheries; in addition those chicks should be transported in properly cleaned and disinfected crates. Birds should be housed in buildings that can be properly cleaned between flocks and this must be meticulous prior to disinfection (Van Hoorebeke, 2010a and 2010b). There should be stringent all in/all out procedures with houses empty for a sufficient time between flocks. A recent EU study indicated that the conventional battery cages may present higher risk for Salmonella than floor raised poultry (Van Hoorebeke, 2010a). 

The feed mills should operate with a Salmonella control using HACCP and feed should be heat-treated. All forms of stress increases risks of Salmonella shedding and therefore thinning of flocks should be avoided. 

Costs associated with Salmonella control 

Prevention of Salmonella infection imposes direct costs attributed to enhanced biosecurity, vaccination, feed additives and surveillance.  In the event of confirmed Salmonella in the layers; flock depletion, pasteurisation or destruction of eggs, cleaning, disinfection and a prolonged down time before repopulation brings significant expenditure. Indirect costs including increased liability insurance and loss of goodwill following a public health incident may be significant especially if a brand is implicated. 

How can the producer benefit from less Salmonella?

Consumer confidence and market shares
The impact of sales in case of human salmonellosis outbreaks is considerable and the public purchasing patterns are greatly influenced by news about Salmonella outbreaks in food. The time, effort and resources required to restore consumer confidence are very high and the benefit of avoiding egg-related Salmonella outbreaks should not be underestimated.

As the level of Salmonella continues to decrease and there is continued emphasis to reduce Salmonella in food production, the public health demands for Salmonella free products will increase. Many consumers are willing to pay more for a product that has been produced to higher standards of animal and public health. The international trade is furthermore largely governed by hygienic standards of food production and Salmonella free products will likely be required in the future.

In the United Kingdom this is exemplified by the Lion Quality Code of Practice, introduced in 1998, to ensure that eggs have been produced to the highest standards of food safety. The measures include the compulsory vaccination against Salmonella Enteritidis, independent auditing, improved traceability, on-farm and packing station hygiene controls and a ‘best-before' date indicating that the eggs are fresher than required by law. The mark now appears on 85% of UK eggs and has been successful in restoring confidence in the industry.

Production Interventions
Several interventions to reduce Salmonella in hens will also enhance the animal health and productivity. Hygienic measures result in a lower microbial load and thereby improve health status and production parameters. Additionally, eliminating stress in the birds not only minimises Salmonella shedding but also provide better health, feed conversion and productivity. Another control measure to reduce Salmonella shedding is the use of mannan-oligosaccharides (Bio-Mos, Alltech Inc.) in-feed to optimise gut health and prevent Salmonella colonisation (Figure 2.). Fernandez (2000) demonstrated a reduction in colonisation of Salmonella Enteritidis in the caeca of young chicks (46 vs. 79%) when fed Bio-Mos. In addition to decreasing Salmonella levels, Bio-Mos has been shown to improve feed conversion rate and egg production. Gracia (2004) noted a 2.3% increase in egg production and a 1.4% improvement in feed conversion ratio when Bio-Mos (1 kg/ton) was added to the diets of laying hens.

Conclusions
The current challenge of European egg producers to control Salmonella at the same time that the cage hen production system is abolished may seem overwhelming and counter-productive. Studies have indicated that hens in floor production systems and enriched cages do not seem to pose an increased risk for Salmonella and newer housing structures minimise the Salmonella risks. Hygienic practices and measures to reduce stress in birds not only reduce Salmonella shedding in birds but also improve bird health and productivity. To produce Salmonella-free products, one needs to consider not only the efficacy of strategies, but also the long-term rewards. Salmonella control interventions such as supplementing the diet with Bio-Mos can reduce Salmonella shedding, whilst simultaneously increasing egg production. These measures allow egg producers to capitalise on Salmonella control plans. 

References

EU (2003) REGULATION (EC) No 2160/2003 OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL of 17November 2003 on the control of Salmonella and other specified food-borne zoonotic agents. OJL 325, pp 1-15
http://eur-lex.europa.eu/LexUriServ/site/en/oj/2003/l_325/l_32520031212en00010015.pdf
EU (2006) COMMISSION REGULATION (EC) No 1168/2006 of 31 July 2006 implementing Regulation (EC) No 2160/2003 as regards a Community target for the reduction of the prevalence of certain Salmonella serotypes in laying hens of Gallus gallus and amending Regulation (EC) No 1003/2005.OJL 211, pp 4-8
http://eur-lex.europa.eu/LexUriServ/site/en/oj/2006/l_211/l_21120060801en00040008.pdf
Collard J.M., et al., 2008. Drastic decrease of Salmonella Enteritidis isolated from humans in Belgium in 2005, shift in phage types and influence on foodborne outbreaks. Epidemiol Infect, 136:771-781.
EFSA (2007) Report of the Task Force on Zoonoses Data Collection on the Analysis of the baseline study on the prevalence of Salmonella in holdings of laying hen flocks of Gallus gallus. Available online: www.efsa.europa.eu
EFSA Panel on Biological Hazards (BIOHAZ), 2010. Scientific Opinion on a quantitative estimate of the public health impact of setting a new target for the reduction of Salmonella in laying hens. EFSA Journal, 8(4):1546, Available online: www.efsa.europa.eu
EFSA Panel on Biological Hazards (BIOHAZ); Scientific Opinion on a quantitative estimate of the public health impact of setting a new target for the reduction of Salmonella in laying hens. EFSA Journal 2010; 8(4):1546. Available online: www.efsa.europa.eu
Fernandez F., et al., 2000. Evaluation of the effect of mannan-oligosaccharides on the competitive exclusion of Salmonella Enteritidis colonization on broiler chicks. Avian Pathol. 29:575-81.
Gracia M.L., et al., 2004. Effect of mannan oligosaccharides supplementation to laying hens. Poult. Sci. 83(Suppl. 1):397
Haagsma J., Van et al., 2009. Disease burden and costs of selected foodborne pathogens in the Netherlands, 2006. RIVM Reports.
Korsgaard H., et al. , 2009. The effects, costs and benefits of Salmonella control in the Danish table-egg sector. Epidemiol Infect, 137:828-836.
Spring P., et al. , 2000. The effects of dietary mannan oligosaccharides on cecal parameters and the concentrations of enteric bacteria in the ceca of Salmonella-challenged broiler chicks. Poult. Sci. 79:205-211.
Van Hoorebeke, S. et al., 2010a. Determination of the within and between flock prevalence and identification of risk factors for Salmonella infections in laying hen flocks housed in conventional and alternative systems. Prev. Vet. Med. 94:94-100
Van Hoorebeke, S. et al., 2010b. The age of production system and previous Salmonella infections on-farm are risk factors for low-level Salmonella infections in laying hen flocks. Poult. Sci. 89:1315-1319.