Guidance

Preventing the introduction of exotic PRRSV strains into Great Britain in imported live pigs or semen

Published 27 January 2025

1. Background

• Porcine reproductive and respiratory syndrome (PRRS) is an economically important disease of pigs which occurs worldwide. The disease has significant effects on pig health and welfare, contributing to porcine respiratory disease complex, neonatal piglet mortality, infertility, abortions and stillbirths. Its immunosuppressive effect exacerbates other diseases, including those due to bacterial pathogens, meaning that it is a driver of antimicrobial use.
• PRRSV is divided into PRRSV-1 and PRRSV-2 which differ genetically and do not cross protect. PRRSV-2 tends to cause more severe disease than PRRSV-1, however more virulent strains of PRRSV-1 have been described in other parts of Europe outside Great Britain (GB). For example, subtype 3 occurs in Eastern Europe and the Rosalia strain occurs in Spain.
• PRRS was first seen in the United Kingdom in 1991 and PRRS due to PRRSV-1 has since become an important endemic disease. No PRRSV-2 has been detected in the GB pig herd to date.
• In 2021, detection of PRRSV (1 or 2) became a reportable disease in GB. This means that a test result which indicates that an animal or carcase is or is reasonably suspected to be infected with PRRSV-2 must be reported to APHA as soon as possible. For PRRSV-1, reporting of test results which indicate infection is monthly.

2. Actions to prevent introduction of exotic PRRSV strains

• The Animal and Plant Health Agency (APHA), Pig Veterinary Society (PVS), Agriculture and Horticulture Development Board (AHDB), National Pig Association (NPA) and British Pig Association (BPA) regularly raise awareness of the risks of importing novel strains of PRRSV into GB and the threat they represent to the national pig herd.
• Anyone importing live pigs or semen should follow the guidance in the NPA protocol for the importation of live breeding pigs into GB. It is now a Red Tractor standard that the NPA import protocol is followed by Red Tractor-assured herds.
• Semen should only be sourced from PRRSV-negative, unvaccinated herds. There are also compulsory requirements for PRRSV testing for boars to enter EU-approved semen collection centres under Artificial Breeding Control legislation.
• Discussions between the importer’s private veterinary surgeon and the vet for the herd from which pigs or semen are being imported should take place prior to purchase or importation.
• Negative pre-import test results for PRRSV are vital. Testing pigs after importation risks importers being faced with difficult decisions, such as whether to return or cull pigs that test positive.
• The NPA protocol has guidance on the isolation facility that pigs should be kept in post-import, these may also be subject to APHA approval. The importer should seek advice from their vet when setting up an isolation unit.