Serological Salmonella monitoring in German pig herds: results of the years 2003-2008

Abstract

The implementation of the European regulations regarding zoonoses demands objective and scientific statements regarding the status of the Salmonella prevalence in the national pig herds of all EU member states. Since 2002, the "QS Qualität und Sicherheit GmbH" has carried out serological Salmonella monitoring in German finishing pig herds. All data generated within the monitoring system are entered into the central database Qualiproof(®) (Qualitype AG, Dresden). The dataset investigated included 5,324,532 samples taken between January 1, 2003 and December 31, 2008, originating from 22,490 herds. Blood sera or meat juices were sampled following a standardized sampling scheme (up to 60 samples per year and herd, depending on herd size) using one of four evaluated ELISA-tests. Herds were classified into three categories I (0-20%), II (>20-40%), or III (>40%) by their percentage of yearly positive samples, which was re-calculated quarterly. The number of participating herds increased continuously since the start of the monitoring programme, with regional differences in the degree of participation. In 2008, 10.8% of all samples were positive. Adjusted for the distribution of samples in the German districts, the Salmonella prevalence in Germany was 7.9%. In general the distribution of herds in the categories was relatively stable over time. In the fourth quarter of 2008, 81.9% of the herds were allocated to category I, 14.0% to category II, and 4.0% to category III. However, the prevalence of Salmonella tended to decrease in herds that participated over a longer period. Differences could be found between German geographical regions. Seroprevalences were higher in the Northwest and the Northeast than in the South. This might be due to the relationship between Salmonella seroprevalences and farm densities per district, which were both higher in Northern than in Southern Germany. The Salmonella monitoring system will contribute to the reduction of the Salmonella prevalence in German pork production, when it is supplemented by control measures.