Salmonella is a major cause of food-borne illness in humans. Farm animals and foods of animal origin are important sources of human Salmonella infections. Therefore, in order to reduce the incidence of human salmonellosis in the European Union, Community legislation foresees the setting of Salmonella reduction targets for food/animal populations, including breeding pigs. To underpin such targets, a series of baseline surveys have been conducted to ascertain the occurrence prior to the implementation of such Community legislation. This fifth European Union-wide baseline survey was carried out at farm level todetermine the prevalence of Salmonella in pig breeding holdings. The herds were randomly selected from holdings constituting at least 80% of the breeding pig population in a Member State.
Sampling took place between January 2008 and December 2008. A total of 1,609 holdings housing and selling mainly breeding pigs (sows or boars of at least six months of age kept for breeding purposes) (breeding holdings) and 3,508 holdings housing breeding pigs and selling mainly pigs for fattening or slaughter (production holdings) from 24 European Union Member States, plus Norway and Switzerland were included in the survey. In each selected breeding and production holding, fresh voided pooled faecal samples were collected from 10 randomly chosen pens, yards or groups of breeding pigs over six months of age, representing the different stages of production of the breeding herd (maiden gilts, pregnant pigs, farrowing and lactating pigs, pigs in the service area, or mixed). The pooled samples from each holding were tested for the presence of Salmonella and the isolates were serotyped. The country level and European Union level prevalence presented in the report are apparent prevalence, meaning that the prevalence estimates do not account for imperfect sampling and test characteristics.
The overall European Union prevalence of Salmonella-positive holdings with breeding pigs was 31.8% and all but one participating Member State detected Salmonella in at least one holding. Twenty of the 24 Member States isolated Salmonella in breeding holdings and at European Union level 28.7% of the holdings was estimated to be positive for Salmonella. This prevalence varied from 0% to 64.0% among the Member States. The estimated European Union prevalence of breeding holdings positive to Salmonella Typhimuriumand to Salmonella Derby was 7.8% and 8.9%, respectively.
Twenty-one of the 24 Member States isolated Salmonella in production holdings and at the European Union level 33.3% of the production holdings was estimated to be positive for Salmonella. This prevalence varied from 0% to 55.7% among the Member States. The estimated European Union prevalence of production holdings positive for Salmonella Typhimurium and Salmonella Derby was 6.6% and 9.0%, respectively. For the two non-Member States, Switzerland detected Salmonella in both breeding and production holdings while Norway did not detect any Salmonella in its surveyed holdings.
The number of different Salmonella serovars isolated in breeding holdings and production holdings across the European Union was 54 and 88, respectively. Salmonella Derby was the most frequently isolated serovar in both breeding and production holdings, detected in 29.6% and 28.5% of the Salmonella-positive holdings, respectively. The next most commonly isolated serovar wasSalmonella Typhimurium accounting for 25.4% and 20.1% of Salmonella-positive breeding holdings and production holdings, respectively. These serovars were also commonly found in the EU-wide baseline survey of fattening pigs at slaughter in 2006-2007. The next most frequently reported serovars were Salmonella London,Salmonella Infantis and Salmonella Rissen both in breeding and production holdings and each accounted for approximately 7% of the positive holdings, in each type of holding. Also Salmonella isolates with the incomplete antigenic formula 4,,12:i:-, which are likely to be related to the recent emergence of monophasic Salmonella Typhimurium, were reported by several Member States.
Salmonella infection in breeding pigs may be transmitted to slaughter pigs through trade and movement of live animals and contamination of holding, transport, lairage and slaughter facilities. This may lead to Salmonella-contamination of pig meat and consequently to human disease. Further studies in surveillance and control methods for Salmonella in breeding pigs as well as in the public health importance of consumption of meat from culled breeding pigs are recommended. Also investigations on the epidemiology of monophasic Salmonella Typhimurium would be welcome. The results of this survey provide valuable information for the assessment of the impact of Salmonella transmission originating from holdings with breeding pigs as a source of Salmonella in the food chain. These baseline prevalence figures may be used for the setting of targets for the reduction of Salmonella in breeding pigs, to follow trends and to evaluate the impact of control programmes.