Alternative samples for Porcine Reproductive and Respiratory Syndrome surveillance in an endemic PRRSV-1 infected breeding herd: a descriptive study

AbstractKnowing PRRSV status is essential to design herd management protocols. For this, weaning-age pigs are a key subpopulation. In the last years, several alternatives to blood sampling have been tested because of easier, welfare friendly and cost saving tools. Moreover, most of them allow to test more animals and then, seem to be more sensitive in case of low prevalence scenario. However, these studies have been implemented mainly in PRRSV-2 infected herds. The first objective of our study was to compare the rate of detection of PRRSV-1 by RT-qPCR in individual serum samples, family oral fluid samples (FOF) and udder wipes (UW) collected the day before weaning. The second objective was to evaluate the interest of pooling. The study was performed on a 200-sows farrow-to-finish farm, PRRSV-1 infected and unstable. 119 litters were sampled (one sample type per litter). The rate of detection of PRRSV-1 in blood samples, FOF and UW was 10.9%, 7.6% and 0.8%, respectively. The agreement between sera and FOF was almost perfect even if detection capacity of sera was numerically superior to FOF. The Ct values on sera were statistically lower than FOF ones. Two modalities of pooling (1/3 and 1/5) were tested for sera and FOF. They showed that both modalities did not impact the qualification neither of the litter not of the batch PRRSV classification. On the other hand, even pooled by 3, most of the FOF pools gave negative results misclassifying many litters and batches. In the conditions of our study, in a PRRSV-1 infected scenario, FOF seemed to be a good alternative to blood sampling only when analysed individually and so a more costly alternative.