Salmonella seroprevalence at the population and herd level in pigs in The Netherlands

The aim of this study was to provide baseline data on the population and he rd Salmonella seroprevalence in sows and finishers. For the population esti mates in 1996 and 1999 and the herd prevalences for sows and gilts, blood s amples from swine vesicular disease (SVD) and pseudorabies monitoring progr ammes were used and tested in an indirect Salmonella enzyme-linked immunoso rbent assay (ELISA). The herd prevalence for finishers was determined using blood samples collected at two slaughterhouses. The population prevalence for finishers in 1996 and 1999 was 23.7 and 24.5% . respectively, and for sows 40.5 and 60.4%, respectively. The prevalence i n free range (FR) finishers was significantly higher (44.6%) than in intens ively housed finishers in 1999, identifying a hazard group for possible ext ra pork and pork product contamination. Of 406 finishing herds, 9% were com pletely seronegative for Salmonella (cur-off OD% > 10). Of these 406 finish ing herds, 69.7% had Salmonella-status I (low prevalence), 21.7% status II (moderate prevalence) and 8.6% status III (high prevalence) (cut-off OD% > 40). In 46 multiplying sow herds, 20 breeding sow herds and 20 matching rep lacement gilt herds, the average herd prevalences were 54, 44.4 and 19.3%, respectively. Two gilt herds were completely seronegative. The prevalence i n the gilt herds was never higher than in the matching breeding sow herds. Agreement on methodology and calibration of ELISA tests would make these re sults comparable between countries and is a prerequisite for a co-ordinated and integrated program to reduce Salmonella in pork in the European Union. (C) 2001 Elsevier Science B.V. All rights reserved.