Porcine reproductive and respiratory syndrome virus seroprevalence in Scottish finishing pigs between 2006 and 2018

Background: Porcine reproductive and respiratory syndrome (PRRS) is a major endemic pig disease worldwide and is associated with considerable economic costs. Methods: In Scotland, three abattoir surveys were conducted in 2006 (158 farms), 2012-2013 (94 farms) and 2017-2018 (97 farms) to estimate seroprevalence to PRRS virus (PRRSV) in commercial finishing pigs. These surveys covered around 79%, 59% and 66% of the Quality Meat Scotland assured farms slaughtering pigs in Scotland in 2006, 2012-13 and, 2017-18 respectively. In the 2006 survey, six pigs per farm were sampled and tested using the CIVTEST SUIS PRRS E/S test. In the 2012-2013 and 2017-2018 surveys, 10 pigs per farm were sampled and tested using the IDEXX PRRS X3 Ab test. A farm was considered positive if it had one or more seropositive samples. Results: The prevalence of positive farms was 45.6% (95% CI: 38.0-53.4), 47.8% (95% CI: 38.1-57.9) and 45.4% (95% CI: 35.8-55.3) in the 2006, 2012-2013 and 2017-2018 surveys, respectively, and 70%-75.5% farms did not change their status between sampling periods. Conclusion: The prevalence of PRRSV exposure in Scottish pig herds was high and changed little from 2006 to 2018. These surveys have informed planning for a prospective PRRS control programme in Scotland.