Kontext

Porcine Reproductive respiratory Syndrome (PRRS) is now the most economically important disease for the global pig industry.  The estimated cost of PRRS within the EU is 1.5 billion euros, approximately 5-10 euros/pig.   Within Northern Ireland, PRRS was first identified in 1997 and has been estimated to cost approaching 40% of net margin per pig unit. Within the UK, in excess of 50% of sows and approximately 50% of all pigs are estimated to be infected with PRRS.
The issue with PRRS is not only the clinical impact of the virus itself but the fact that the PRRS virus multiplies inside the macrophages in the lungs.  Hence, instead of the macrophages destroying the virus, they become the replication ground for PRRS. Up to 40% of macrophages can be destroyed, thus supressing the immune system, allowing bacteria and other viruses to proliferate such as pleurisy.
PRRS is a complicated disease with no stable/long term vaccine as the PRRS virus undergoes rapid evolution showing antigenic, pathogenic and genetic variations.  This has important implications for vaccine development but also highlights the importance of controlling the disease via strict biosecurity and management in conjunction with an effective vaccination programme.