Detection of porcine reproductive and respiratory syndrome virus (PRRSV) and influenza A virus (IAV) in oral fluid of pigs.

Recently oral fluid has become a novel sample type for pathogen nucleic acid and antibody detection, as it is easy to obtain with non-invasive procedures. The objective of the study was to analyze porcine reproductive and respiratory syndrome virus (PRRSV) and influenza A virus (IAV) circulation in growing pigs from three Polish production farms, using Real Time PCR and ELISA testing of oral fluid and serum. Oral fluids were collected every 2weeks, in the same 3-4 pens of pigs aged between 5 and 17weeks. Additionally, blood samples were collected every 4weeks from 4 pigs corresponding to the same pens as oral fluid and tested for the presence of PRRSV nucleic acid (pooled by 4) and antibodies. In farm A no PRRSV circulation was detected and only maternal antibodies were present. In farm B and farm C antibodies to PRRSV in serum and oral fluid were detected in most samples. In farm B PRRSV Type 1 was detected in 80.9% of oral fluid samples and in 58.3% of serum pools, and in farm C in 92.8% of oral fluid samples and 75% serum pools. Striking differences were observed between different pens in PRRSV detection patterns. In farms B and C ORF5 sequence analysis showed the presence of wild type strains which were about 84-85% identical to the modified live vaccine used. In all three farms two waves of IAV shedding with oral fluid were detected, in weaners and fatteners.