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Bulletin No. 19 - Fall 2004
18th IPVS Congress, Hamburg, Germany, 2004Porcine Reproductive and Respiratory Syndrome (PRRS)
PESENTE P, SANDRI GP, SPERATI RUFFONI L, CAMPAGNARI E
Infection and reinfection with homologous and heterologous porcine reproductive and respiratory virus (PRRSV) strains: practical aspects
Proceedings of the 18th IPVS Congress, Hamburg, Germany, 2004 - Volume 1:24
Ten initially PRRSV-negative pigs of 21 days of age were intramuscularly inoculated with a strain of PRRSV (strain A). Animals were monitored for clinical signs, the presence of PRRSV in blood and in oropharyngeal scrapings by nested-PCR and immune response by ELISA. Pigs were inoculated again with the same strain at day 140 and two weeks later (day 154) with an heterologous strain (strain B showing 7.8% difference in its amino acid sequence with strain A). Following re-infection with the homologous strain, none of the pigs showed clinical signs suggesting that protection against an homologous strain lasts at least 140 days. Following challenge with the heterologous strain, no clinical signs were observed but viremia was prolonged and a significant seroconversion occurred in all animals which can then excrete this heterologous strain of PRRSV. The response to a heterologous strain is clearly different from that to the homologous strain. As a consequence, acclimatization of replacement animals is to consider a critical step and particular care should be taken to introduce only pigs acclimatized with the homologous strain. Testing oropharyngeal scrapings by nested-PCR appears a useful tool for the identification of carrier animals.
