Porcine Reproductive and Respiratory Syndrome control in Asia.

Porcine Reproductive and Respiratory Syndrome control in Asia. Porcine Reproductive and Respiratory Syndrome (PRRS) continues to be one of the most economically devastating viral diseases affecting pig farms in major swine producing countries in Asia. Recent data from Japan showed a reduction of 53.7g per day on ADG and an increase of 2.2% in post-weaning mortalities in PRRS positive farms as compared to the production performance of PRRS negative farms. However, although many farms are infected, the clinical impact of PRRS infection varies. Different factors lead to such variability in the clinical presentation including the strain infecting the herd, the type of production (single site farrow-to-finish vs multi-site systems), the season (weather), the presence of co-infections prior to PRRS introduction, the pig density in the immediate locality of the farm and the way the farm manages their replacement breeders. Effective control programs focus on addressing the predisposing factors through management changes and on ensuring herd immunity is well established. Different approaches have been done to stabilise herd immunity to PRRS including exposing the sow herd to infected animals or live virus and doing whole herd vaccination. However, although vaccination is increasingly used in Asia to reduce the impact of PRRS, the results have been variable. Many factors may have contributed to the differences in efficacy of vaccines, but the major difference is PRRS vaccine strain used in the final formulation and its ability to provide effective cross protection against the predominant field PRRS strains.