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Salmonella levels in laying hen flock holdings across the European Union: final report published

The European Food Safety Authority (EFSA) has published the final version of their study on Salmonella levels in layer flock holdings across the European Union (EU) [1], following up on their earlier preliminary report published in June 2006 [2]. Tests on dust and other material found in poultry houses, as well as bird faeces, indicates the levels of Salmonella spp. on the holding . Sampling of the holdings was done between 1 October 2004 and 30 September 2005. The baseline results from this study have provided the scientific basis on which to set targets for the reduction of salmonella prevalences in EU commercial laying flocks [3], which should in turn lead to less salmonella contamination of eggs.

Salmonella spp was detected in 1486 holdings in the EU. This resulted in a Community weighted observed Salmonella spp. holding prevalence of 30.8% (95% CI= 29.8% - 31.8%). There was large inter-country variation, ranging from a minimum of 0% (Luxembourg and Sweden ) to a maximum of 79.5% (Portugal). The presence of S. Enteritidis/S. Typhimurium was detected in 986 holdings in the EU. This resulted in a Community weighted S. Enteritidis/S. Typhimurium observed holding prevalence of 20.4% (95% CI= 19.5% - 21.3%) with a range from 0% (Ireland, Luxembourg, Latvia, and Sweden ) to 62.5% (Czech Republic ).

Of all the member states, the United Kingdom showed the sixth lowest observed holding prevalence for Salmonella spp, with 11.9% (95% CI= 9.9% - 14.7%). The holding prevalence for the two most common serovars Salmonella Enteritidis and/or Typhimurium was 7.9% (95% CI= 6.2% - 10.1%). These proportions for the UK compare favourably with most of the other EU Member States.

Salmonella contamination was more likely to be identified on holdings with larger numbers of laying birds than those with fewer birds, although this might reflect the sampling method. Vaccination of the hens in the flock against Salmonella was associated with a lower risk of being Salmonella positive, except for holdings infected with S. Typhimurium. There will be mandatory vaccination of layer hens against Salmonella from 2008 onwards for layer hen holdings in Member States with a Salmonella prevalence of 10% or more [3].

Due to the design of the study, which resulted from the pragmatic decision to sample only one flock per holding, the true holding prevalence is likely to be higher than the observed, as some of the holdings detected negative may house one or more positive flocks that were not sampled and hence not detected. The observed Salmonella prevalences in the study are likely to be underestimated, but despite this they are generally higher than those reported in national zoonoses reports by the Member States, where a variety of monitoring methods are used.

Thirteen Member States submitted additional information on the antimicrobial susceptibility of Salmonella isolates. In general, a higher proportion of antimicrobial resistant isolates was reported for S. Typhimurium than for S. Enteritidis and other serovars. No isolates from UK flocks were resistant to ciprofloxacin or cephalosporins, which are the most likely to be used for severe salmonella infections in humans.

In Europe, Salmonella is now controlled in the egg production chain under Regulation (EC) No 1168/2006 [4]. Every Member State will have to work towards reducing the number of laying hen holdings contaminated with Salmonella by a specific minimum percentage each year, with steeper targets for Member States with higher levels of Salmonella. The first target deadline is set for 2008. It is also planned under this Regulation that from January 2010, eggs from Salmonella infected flocks will be treated in a manner that guarantees the elimination of Salmonella, e.g. the heat treatment of contaminated eggs. Contaminated eggs will therefore be required to be sent for processing into egg products.

Information
Salmonella is an important cause of foodborne disease in humans throughout the world and is a significant cause of morbidity, mortality and economic loss. Hens' eggs which are derived from flocks infected with Salmonella Enteritidis are an important source of human infections due to this serovar. S. Enteritidis is the serovar which causes more than 50% of human infections with Salmonella in the EU. The second most reported serovar in humans is S. Typhimurium, which is less often associated with the consumption of hens' eggs.

References
1.EFSA. 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. Parma , Italy : EFSA, 21 February 2007. Available at: <http://www.efsa.europa.eu/en/science/monitoring_zoonoses/reports/report_finlayinghens.html >

2. Health Protection Agency. Baseline study on the prevalence of Salmonella spp in laying hen flocks in the European Union. Commun Dis Rep CDR Wkly [serial online] 2006 [accessed 23 January 2007]; 16(24): news. Available at
<http://www.hpa.org.uk/cdr/archives/2006/cdr2406.pdf >.

3. European Commission (EC). Commission Regulation (EC) No 1177/2006 of 1 August 2006 implementing Regulation (EC) No 2160/2003 of the European Parliament and of the Council as regards requirements for the use of specific control methods in the framework of the national programmes for the control of salmonella in poultry. Official J European Union L212 , 3-5. Available at:
<http://eurlex.europa.eu/LexUriServ/site/en/oj/2006/l_212/l_21220060802en00030005.pdf>.

4. European Commission (EC). 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. Official J European Union L211 , 4-8. Available at:<http://eurlex.europa.eu/LexUriServ/site/en/oj/2006/l_211/l_21120060801en00040008.pdf>.