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Bulletin No. 22 - Summer 2005
VirologyPorcine Reproductive and Respiratory Syndrome (PRRS)
PESENTE P, REBONATO V, SANDRI GP, GIOVANARDI D, SPERATI RUFFONI L, TORRIANI S
Analisi della variabilità genetica del virus della sindrome riproduttiva e respiratoria del suino nel Nord-Italia tra il 2002 e il 2004: modalità di diffusione e ripercussioni nella gestione degli allevamenti [Analysis of porcine reprod
Società Italiana di Patologia ed Allevamento dei Suini - Proceedings, 2005, 253-261
The dynamics of PRRSV variability in swine herds in Northern Italy was investigated on the base of the nucleotide and amino acid sequences of ORF5 and ORF7. The results confirm a high variability between the Italian strains which accounts for the ability of PRRSV to elude the immune system. The introduction of infected animals appears to be the main source of spread of PRRSV. Indeed a high percentage of strains identified in growing herds had a molecular equivalent in the corresponding breeding herds. This study also provided information concerning the efficacy of acclimatization. In half of the cases, acclimatization allowed to achieve the circulation of a single variant of the virus and a reduction of the clinical expression of PRRS. In the remaining half, two variants were identified in 2/3 of the cases whereas acclimatization had no positive effect in the remaining 1/3 of the cases. The strategy of acclimatization is thus highly advisable in breeding herds where only one variant of PRRSV circulates and where the risk of new introduction is low.
