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Bulletin No. 17 - Winter 2003
VirologyPorcine Reproductive and Respiratory Syndrome (PRRS)
BØTNER A
Experiences with eradication of PRRS in Danish swine herds.
Association Française de Médecine Vétérinaire Porcine, Maisons-Alfort, 4-5 December 2003
The tricky situation of PRRS in Denmark has arisen from the introduction, in 1996, of a modified live vaccine based on an American strain of PRRSV (Ingelvac® PRRSV MLV, Boehringer Ingelheim) which has resulted in outbreaks of reproductive failure (abortions and stillborn piglets, mortality in suckling piglets) and the spread of the American (US) type of the virus among the Danish pig population. Currently both the European (EU) and the US types of PRRSV are circulating in Denmark. Two serologic tests, i.e. immunoperoxydase monolayer assay (IPMA) and double-blocking ELISA, allow to differentiate between the EU and US strains of PRRSV, the latter being routinely used for large scale screening whereas the former is used for serologic herd profiles. On a herd level, the sampling should be carried out in 4-5 pigs in each of the different age groups. The eradication strategy consists in: partial depopulation, one-way flow of pigs in the production and introduction of only immune breeding animals in the herd. The first objective is to achieve the stabilization of the sow unit with no virus shedding in order to obtain PRRSV-free piglets. However the risk of re-infection is still quite high due to the widespread of the virus.
