Infectious Diseases 2006

Infectious Diseases 2006

Salmonella in the European Union

18 June, 2006

In the European Union, Salmonella enterica serotypes Enteritidis and Typhimurium are the Salmonella types most frequently associated with human illness. Eggs are considered the main source of human salmonellosis in Europe and in many other countries worldwide.
Preliminary results of a Salmonella baseline study, conducted on commercial large-scale laying hen holdings with at least 1000 laying hens (Gallus gallus) in all European Union countries and Norway, have just been published.
This study is the first of its kind to have been carried out in the European Union. The new EU zoonoses legislation introduced in 2003 requires an EU target to be set to reduce Salmonella prevalence in laying hens, and the aim of the study was to estimate the observed prevalence of Salmonella in laying hen holdings at EU-level as well as for each member state. The study was designed according to European Commission specifications.
A total of 5317 laying hen holdings in the EU were included in this study, but for the most part, complete data from 4797 holdings were used to analyse the results. Sampling of the holdings was done between 1 October 2004 and 30 September 2005, and samples were taken during the last nine weeks of egg production. Five faecal samples and two dust samples were taken from only one randomly chosen flock per holding, which means the observed prevalence in holdings must be considered as a minimum.
Results
The highest prevalences of S. Enteritidis and S. Typhimurium were found in the Czech Republic, Poland and Spain, with S. Enteritidis and/or S. Typhimurium detected on 63%, 56% and 52% of holdings respectively. No zoonotic Salmonella types were detected in any flocks in Sweden, Norway, or Luxembourg.
The results also show that 20% of all large-scale laying hen holdings in the European Union are bacteriologically positive for S. Enteritidis and/or S. Typhimurium. The presence of any Salmonella species on EU large-scale holdings was 31%. There is large inter-country variation: in some countries, no Salmonella was detected, while other countries had prevalences of up to 80%.
The number of positive samples from a holding varied between 1 and 7, and a large number of the holdings were found positive on the basis of only one or two positive samples. Dust samples were more likely to be found positive for S. Enteritidis and/or S. Typhimurium than faecal samples. Antibiotic treatment of the laying hens within the two weeks before sampling did not seem to affect the detection rates for S. Enteritidis and/or S. Typhimurium.
By far the most frequently isolated Salmonella serovar from the laying hen flocks was S. Enteritidis, which was isolated in 18 countries and accounted for 51% of the reported isolates. S. Infantis was the second most frequently encountered isolate (8%), isolated in 14 countries, and S. Typhimurium was the third (5%), isolated in 14 countries. The distribution of the isolated serovars varied between the countries; however, S. Enteritidis was the most frequent type in 15 member states.
Salmonella prevalences will be used to set reduction targets
The prevalence of Salmonella observed in holdings of laying hen flocks in this study underlines the need to control Salmonella in the table-egg production sector. The final report will be published in October 2006, but these baseline results will be used to set the targets for the reduction of Salmonella prevalences in EU commercial laying flocks before then (Eurosurveillance.org).