Abstract
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).
Highlights
Porcine Reproductive and Respiratory Syndrome (PRRS) has a significant impact on the health and welfare of pigs and has become enzootic in most pig production areas [18]
Even if we could expect a vertical transmission from sow to piglets, no PRRS virus (PRRSV) RNA was detected in all these samples
No horizontal transmission from sow to piglets and within piglets in the batch was observed as no PRRSV RNA was detected in serum samples collected from dueto-wean piglets born after the sow mass vaccination (SMV)
Summary
Porcine Reproductive and Respiratory Syndrome (PRRS) has a significant impact on the health and welfare of pigs and has become enzootic in most pig production areas [18]. Improvements in detection and management of PRRS virus (PRRSV) in production systems continue to be challenging for swine producers and veterinarians. To assess the success of such protocols, the first step is to evaluate the status of the breeding herd, usually classified as naive, stable or unstable. This classification is described by the American Association of Swine Veterinarians (AASV) guidelines [4] and is based on blood samples (BS) collected from due-to-wean piglets and (2021) 7:6 tested by qPCR pooled by five. This method aims to generate evidence of absence of viral replication and transmission in pigs
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