SE Control: A European perspective

For many years, European authorities have promoted a “Farm-to-Fork” philosophy in an attempt to reduce human cases of salmonella food poisoning. 

FOOD SAFETY CONCERNS Strategies that the EU poultry sector have used in their feed mills, farms, hatcheries and processing plants in an effort to reduce all salmonella species and specifically eliminate S. enteritidis from the products they supply have been vigorously pursued.

For many years, European authorities have promoted a “Farm-to-Fork” philosophy in an attempt to reduce human cases of salmonella food poisoning.  Strategies that the European Union poultry sector has used in its feed mills, farms, hatcheries and processing plants in an effort to reduce all salmo-nella species and specifically eliminate Salmonella enteritidis from the products they supply have been vigorously pursued.  These strategies have have proven remarkably effective but the fight against salmonella continues and the economic cost to the poultry industry has been significant.

 For decades Swedish authorities have pursued an aggressive policy aimed at eliminating salmonella from their food supply chain.  While the remaining member states of the EU have ranged in their commitment to salmonella control programs, there has been a universal application of a “Farm to Fork” philosophy and an increasing evel of consumer education and concern about the prevalence of and risks presented by salmonella contaminated products.  

While human life expectancy in Europe continues to increase and human health and nutritional standards continue to rise, a significant proportion of the European population remains genuinely concerned about the safety of their food. In some situations these concerns may be fanned into genuine fears by a media that can be overzealous in its line of reporting with a tendency to exaggerate the true risks. The adverse publicity arising from a food safety associated product recall can do massive damage to the reputation of a producer or retailer.

Against this background, governments and retailers place greater and greater pressure on the food manufacturing industry to supply salmonella-free products, which at the end of the day is a laudable goal.

 While the epidemiology of salmonella infection of humans is complex, I will review some of the strategies that the poultry industry has used to reduce the prevalence of salmonella species and specifically S.  enteritidis in the food supply chain. In general terms the chicken (meat and egg) has come under more pressure than the turkey or duck sectors. 

ANIMAL FEED
Raw Material Controls – Feed milling practices have evolved significantly over time, often in an effort to reduce the risks of introduction of a contaminant (chemical or microbiological) into the human food chain via food animals.  One of the first areas of control to be focused on was the feed raw material supply chain and most European countries would now have well-documented and rigorously enforced Good Manufacturing Practices (GMPs) and Codes of Practice to ensure that raw materials are stored and transported safely. Examples of controls would include rodent- and bird-proofing of raw material stores, restrictions on the range of materials that trucks are allowed to haul and genuine supplier audit chains to ensure traceability and appropriate quality of the raw materials themselves.  While these controls were often not specifically aimed at salmonella control they have contributed to improved hygiene standards of raw materials.

Another extremely significant factor in reducing the salmonella load of raw materials has been microbiological screening of raw materials by feed mills.  Pressure from the livestock sector has forced feed mills to have a genuine desire for salmonella-free raw materials and any supplier that consistently delivers salmonella contaminated raw materials eventually finds it difficult to find a customer for their products.

While these strategies have been effective at reducing the salmonella load in raw materials and in many countries virtually eliminating S. enteritidis contamination, occasionally (often as a breach of GMP conditions) salmonella will enter the feed mill. Under these circumstances feed manufacturing controls come into play. 
Some people believed that a switch to all vegetable rations would eliminate this risk but this has clearly been shown not to be the case. It should be noted that concerns arising from BSE also triggered a significant reduction in the use of animal proteins in feed mills.
 

The EU Zoonoses Directive has significantly increased the pressure for salmonella control across the EU.

Feed Manufacturing Controls – feed for European breeding flocks, particularly grandparent/great-grandparent flocks, is virtually always subjected to relatively aggressive heat treatment.  A typical regime would involve conditioning feed to 82 C and ensuring it is held at that temperature for at least two minutes.

Some companies would adopt significantly more aggressive heat treatment regimes than this. Even for broiler flocks some member states would legislate that all feed must be heated to at least 81 C whereas other member states will legislate a hygiene outcome, e.g., <1 colony forming unit per gram of Escherichia coli in finished feed. It is essential to recognize that heat treatment is only effective if systems are in place to ensure that all of the feed is effectively heated and can be cooled back to ambient temperatures without re-contamination. Some early heat-treatment systems merely resulted in development of endemic salmonella contamination at the mill.

Organic acid feed additives, sometimes combined with formaldehyde are used to reduce the risks presented by recontamination but the efficacy of these organics continues to be debated.  While products combining formaldehyde have greater efficacy, some member states are reluctant to sanction their use because of health and safety concerns.

The table egg industry has been less enthusiastic about heat treatment and many flocks continue to be fed a non-heat treated mash but organic acids or organic acid/formaldehyde feed additives have been effectively used to reduce the risk of salmonella contamination.
 
“Environmental” Controls – modern European feed mills are designed to ensure that dust is minimized and “treated” feed cannot come into contact with “non-treated” feed during transport to and storage in the finished feed bins.  These controls are carried through to the farm because feed delivery vehicles will not transport raw materials.

Considerable effort will go into ensuring that the feed mill has an effective pest management program to control insects, rodents and wild birds. 

BIOSECURITY
Although the term biosecurity has only become popular relatively recently, for many years there has been a consistent effort to minimize poultry disease and improve food safety across Europe.  This has generated a steady improvement in farm design and anagement practices so that modern poultry houses are relatively easy to clean and disinfect and farm personnel understand the need to control disease vectors such as mice, wild birds and insects. This has allowed many companies to place their birds in a salmonella-free environment and to maintain this freedom through the life of the flock. 

VACCINES
While some companies have managed to implement control strategies that have enabled them to produce S. enteritidis free  products salmonella vaccines have been widely used in broiler breeder and table egg flocks in Europe.  Whether the motive is to add an extra level of protection to a system that is already under control or to minimize the impact of contamination on an operation that has been unable to maintain an S. enteritidis free status, these vaccines have proven very effective in reducing the levels of S. enteritidis entering the food chain. This is  demonstrated very clearly by the significant reduction in human cases of S. enteritidis gastro-intestinal following the adoption of widespread use of commercial inactivated S. enteritidis vaccines.

There is again wide variation in the programs followed in different member states. Some member states will not license live salmonella vaccines, e.g., France while others – e.g., Holland – still use SG9R  vaccine and rely on cross-     protection to control S. enteritidis  However, in the vast majority of member states the egg and broiler breeder sector would use a combination of commercial inactivated and live vaccines.

ANTIBIOTIC TREATMENT
Many EU countries give their poultry farmers the option of treating any breeder flocks that have become contaminated with S. enteritidis or S. typhimurium with antibiotics rather than automatically slaughtering them.  If subsequent environmental monitoring shows that the flock has been cleared of salmonella the flock does not have to be killed. Antibiotics are not, however, routinely used to tackle salmonella contamination.

‘GUT HEALTH’ FEED ADDITIVES
While not a particularly precise grouping, a multitude of products (such as probiotics, organic acids, etc.) have been launched that claim to make the chicken/turkey more resistant to salmonella infection and/or reduce the level of contamination should salmonella colonize the flock.  While there is research data which tends to support some of these claims, in general, few of these products have been used commercially to any extent and, as far as I am aware, even when they have been used the main motive has not been salmonella control/reduction.

HATCHERIES
Through greater attention to cleaning and disinfection and efforts to hatch product from salmonella-positive breeder flocks last, it proved possible to limit cross-contamination.  However, the potential of the hatchery to spread salmonella through an operation remains an ever-present risk. The best option is clearly to have salmonella-free breeder flocks. 

COMPETITIVE EXCLUSION
 A range of CE products have been launched with some success and there is a significant body of research to suggest that CE products can help to protect the very young chick/poult to resist an early salmonella challenge and subsequently reduce the rate of salmonella shedding from infected birds. As a philosophy, CE has been most actively adopted in Scandinavian countries where neo-natal protection is the desired outcome.

While CE is also used to promote gut health, particularly after antibiotic therapy, very few people believe that CE products alone are capable of cleaning a flock which is contaminated with S. enteritidis.

PROCESSING PLANT
 It is common practice in many broiler companies to collect environmental samples from the broiler house prior to depopulation and in the event of finding a salmonella-positive flock to schedule that flock as the last flock of the day to be processed. This both reduces the level of cross-contamination of salmonella negative birds/products and provides the opportunity for thorough cleaning and disinfection of the processing plant after the salmonella positive birds have been processed.

THE FUTURE
 A recent EU pilot survey to determine the effectiveness of salmonella controls in the various EU member states highlighted a wide range in levels of salmonella contamination in different member states. This survey was followed by the recently implemented EU Zoonoses Directive, which will significantly increase the pressure for salmonella control across the EU.  This directive standardizes the sampling and isolation methodologies that must be used, requires each member state to draft and implement a national control program and sets out clear targets for the level of salmonella contamination in layer, breeder and broiler flocks.

This directive has also expanded the range of species whose prevalence must be reduced from S. enteritidis and S. typhimurium to include S. virchow, S. hadar and S. infantis as these are the five salmonella species most commonly associated with human illness.

One of the most interesting scenarios to play out over the next few years will be the potential food safety issues arising from the growth of the extensive poultry production sector.  In a free-range environment, it is extremely difficult to maintain effective biosecurity, which raises the prospects of increased food safety risks against the perceived advantages of a more “natural” production system. 

If one factors in the increased risks of H5N1 avian influenza disease breaks that free-range represent to this debate and the associated consumer fears about this virus, then it will be interesting to see what confidence the consumer eventually develops in free-range agriculture.

Despite the many years of concerted action to eliminate salmonella from the food chain, no country (including Sweden) has managed to develop and maintain a food chain that is completely salmonella free.  However, some countries have managed to achieve production systems which are completely S. enteritidis free and several others are very close to this goal. 

As consumer awareness and concern continues to rise it seem likely that pressure will continue to grow for reduction of salmonella in the food chain and there seems very little appetite in Europe to adopt a strategy that includes intervention at the processing plant to control salmonella levels in the finished product, regardless of the salmonella status of the product leaving the farm. 

While the “Farm-to-Fork” philosophy is certainly not the most economical way to deliver salmonella (or campylobacter free) food it remains the only approach that is acceptable to all European consumers.