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PRRSv Monitoring Using Oral Fluid Sampling: Case Report in French Farrow-to-Finish Farms

09 October 2015

Merial

Nowadays, oral fluid sampling is of great interest for Porcine Reproductive and Respiratory Syndrome virus (PRRSv) monitoring. This method is easier to use, faster and causes less stress to pigs when compared to the standard blood sampling. The objective of this study was to compare PRRSv antibody profiles obtained with these two techniques in two positive but stable herds, write M. Liber et al, Merial.

Two farrow-to-finish farms located in Brittany (France) known to be PRRSv-stable were selected. Mixed vaccination programs using modified live and killed vaccines were in force on the farms in addition to basic hygiene and all-in all-out management.

The absence of clinical signs and recent seroprofiles indicated no to low virus circulation. A transversal study was performed at 4 different ages, farm A: from 6 to 23 and farm B from 5 to 26 weeks of age (WoA).

The pigs in each pen were individually blood sampled and given a rope to chew. A total of 146 sera and 8 rope samples were collected. The samples were assayed for PRRSv antibodies using two commercially available kits (IDEXX PRRS 3XR, IDEXX PRRSV Antibody for Oral Fluid).

Samples with S/P ratio ≥0.4 were considered as positive according to the manufacturer instructions.

Results and Discussion

In farm A, at 6, 9, 12, and 23 WoA, the percentages of positive pigs in the ELISA were 78%, 58%, 8% and 0% and OF E/P ratios were 7.0, 3.3, 0.9 and 0.2, respectively. In farm B at 5, 8, 11 and 26 WoA, the percentages of positives in the ELISA were 43%, 73%, 12% and 0% whereas the OF E/P results were 1.4, 2.2, 0.1, 0, respectively.

No linear correlation between serum prevalence and OF E/P ratio was observed. However, the higher the percentage of positive pigs, the higher the OF E/P and in both farms, profiles of percentage of positive pigs and OF E/P ratio were qualitatively similar.

Data demonstrated a steady decline of maternal antibody level in farm A and possibly a weak and controlled PRRSv circulation during post-weaning in farm B. Fatteners were antibody negative to PRRSv at slaughter age according to the two techniques. These observations confirmed the stable status of the two farms towards PRRSv as well as the effective strategy implemented to control the virus circulation.

Conclusion

Under the conditions of the study, oral fluid samples tested with this PRRSv oral fluid antibody ELISA kit provided extensive information at low cost and confirmed its reliability for PRRSv monitoring in stable herds.

Presented at the 2015 European Symposium of Porcine Health Management

October 2015

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