PRRSV detection by qPCR in processing fluids and serum samples collected in a positive stable breeding herd following mass vaccination of sows with a modified live vaccine.

In the last two decades, in France, Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) stabilization protocols have been implemented using mass vaccination with a modified live vaccine (MLV), herd closure and biosecurity measures. Efficient surveillance for PRRSV is essential for generating evidence of absence of viral replication and transmission in pigs. The use of processing fluid (PF) was first described in 2018 in the United States and was demonstrated to provide a higher herd-level sensitivity compared with blood samples (BS) for PRRSV monitoring. In the meantime, data on vertical transmission of MLV viruses are rare even as it is a major concern. Therefore, veterinarians usually wait for several weeks after a sow mass vaccination before starting a stability monitoring. This clinical study was conducted in a PRRSV-stable commercial 1000-sow breed-to-wean farm. This farm suffered from a PRRS outbreak in January 2018. After implementing a stabilisation protocol, this farm was controlled as stable for more than 9 months before the beginning of the study. PF and BS at weaning were collected in four consecutive batches born after a booster sow mass MLV vaccination. We failed to detect PRRSV by qPCR on PF and BS collected in a positive-stable breeding herd after vaccination with ReproCyc® PRRS EU (Boehringer Ingelheim, Ingelheim, Germany).

Estimation of the diagnostic performance of two ELISAs to detect PCV2 antibodies in pig sera using a Bayesian method.

This study was designed to assess the diagnostic characteristics of two PCV2 ELISAs without a gold standard. Four hundred and sixty-five serum samples from finishing pigs (25 herds) not vaccinated against PCV2 were used. Samples were tested by two ELISAs: an in-house ELISA (I-ELISA) and the commercial SERELISA®PCV2 Ab Mono Blocking kit (S-ELISA). A ROC curve was used to assess the S-ELISA's optimal threshold by taking the I-ELISA as a reference and using the cut-off previously determined by comparison to an cccmonolayer assay (IPMA). This led to an S-ELISA result ≥170 being considered as positive. The sensitivity (Se) and specificity (Sp) of each ELISA were then estimated without a gold standard using a Bayesian approach. The mean Se and Sp values of the I-ELISA were slightly higher than those of the S-ELISA (mean Se I-ELISA=0.90 vs. mean Se S-ELISA=0.86; mean Sp I-ELISA=0.92 vs. mean Sp S-ELISA=0.85). However, the 95% credibility intervals (CI95%) overlapped (Se I-ELISA CI95%=0.85-0.95 vs. Se S-ELISA CI95%=0.82-0.90; Sp I-ELISA CI95%=0.82-0.98 vs. Sp S-ELISA CI95%=0.75-0.94). Both ELISAs appeared to be valuable tools for detecting PCV2 antibodies.