Pathogenic Salmonella detected in just under 30 percent of large-scale laying hen flocks

Since 1992 fewer and fewer people have contracted Salmonella infections. Last year only 52,000 cases were reported in Germany. For the first time more people were infected with Campylobacter germs. This makes salmonellosis the second most frequent foodborne infection in Germany. One main source of infection are eggs, contaminated with Salmonella from infected laying hens, that were not sufficiently heated prior to consumption. Salmonella are to be found in around 30 percent of the large-scale German laying hen flocks. In Scandinavian countries this figure is less than 1 percent, in some eastern European countries it is 65 percent or higher. These are the preliminary results of a pilot study commissioned by the European Commission in the 25 EU Member States. It has now been evaluated by the European Food Safety Authority (EFSA). The final figures will be available in the autumn. In Germany the data were collected by the official control bodies. They were examined and evaluated at the Federal Institute for Risk Assessment (BfR). “The number of Salmonella infections is falling overall”, said BfR President Professor Dr. Dr. Andreas Hensel. ”The results of the pilot study do, however, confirm that we can’t afford to rest on our laurels. The prevalence of Salmonella in laying hens must be reduced further in order to afford consumers even better protection”.

Summer time is Salmonella time. The germs just love heat. Once they are on the scene, they can multiply dramatically and make people sick. A Salmonella infection goes hand in hand with symptoms like diarrhoea, nausea, vomiting and headaches, sometimes with fever as well. Mostly the illness pursues a mild course but there are also serious, typhoidal cases. The most frequent source of infection are contaminated foods, in particular eggs and dishes made from them. Infected laying hens transmit the Salmonella into and onto the eggs. A one-year pilot study aimed to establish how many laying hen flocks are affected. It has now been concluded and provides comparable figures for the first time for all 25 EU Member States. They are to serve as the basis for EU-wide control measures taking into account the specific situation in the individual Member States. With positive test results in 29 percent of the large-scale laying hen flocks, Germany is below the European average of 31 percent. If one only considers the Salmonella types S. Enteritidis and S. Typhimurium, the most dangerous to man, Germany is slightly higher. Up to now it had been assumed that this was in the one-digit percentage range. These figures were based on the voluntary submission of samples to the official control authorities and were not, therefore, representative.

This does not apply to data from the pilot study: they were recorded by the official control authorities of the federal states for a total of 563 selected flocks based on the extensive examination of faeces and dust samples from each flock in a nationwide, representative manner. Salmonella findings from the environment of the hens were also included in the assessment. Positive test results were confirmed (in experiments conducted) at the BfR National Reference Laboratory for Salmonella. They show that the most frequent Salmonella type S. Enteritidis in man is predominant amongst laying hens whereas another human pathogen, the S. Typhimurium variant, was only detected in 2 percent of the flocks. BfR evaluated the German data and passed them on to the Federal Ministry of Food, Nutrition, Agriculture and Consumer Protection and to the European Commission. Following initial assessment there seems to be a link between Salmonella exposure, size of farm and form of husbandry. Larger farms with more than 3,000 laying hens in cages were more frequently affected than those in barn, perchery or free-range systems. Farms with fewer than 1,000 hens were not examined. 

Studies back in the 1990s had already indicated that S. Enteritidis could be a problem with laying hens. This led to the introduction of a compulsory vaccination for laying hens in Germany. The steady drop in reported cases of salmonellosis in human beings by around one-third since 2001 alone was seen as a success of this vaccination. The results of the study do, however, also reveal that further efforts are needed in order to offer consumers even better protection. In future, flocks are therefore to be regularly examined by official bodies and targeted measures taken in the case of positive test results. One option involves imposing constraints on the use of the eggs. By means of this and other measures, the risk to consumers is to be further reduced. At the same time, this responds to the provision of the European Commission envisaging a 30 percent reduction in Germany of the number of flocks contaminated with Salmonella by the end of 2008.

Consumers can protect themselves from contracting a Salmonella infection from eggs by 

  •   always refrigerating eggs, using eggs as fresh as possible and only eating them hard boiled;

  •   sufficiently heating foods made from them and

  •   avoiding any contamination of other foods or objects.

The BfR report on the pilot study is available on the website. The full European report has been published on the EFSA website (

Publikationen - BfR-Wissenschaft 1

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