Impacts of pcv3 and pcv2 on reproductive performance in the vietnamese industrial sow herds

Porcine circovirus (PCV) 2 is a globally prevalent virus causing negative impacts on the swine industry. Controlling PCV2 with vaccines is a mandatory requirement in the farming procedures depending on the prevalence of the virus and farm management system including vaccination program. It should be noted that PCV2d management in the studied farms appeared under control via the effective vaccination program. Since the first descriptions of PCV3 in the US, many publications on the viral pathogenesis and effects on susceptible animals have been conducted, but complete consensus has not been reached. Therefore, an alternative approach to studying the virus is to evaluate its economic impact on swine populations. In this study, 535 blood samples from multi-parous sows and 190 pooled blood samples from replacement gilts from 20 farms in four provinces in southern Vietnam were collected. The results from the current study show that the prevalence rate of PCV3 at the farm level is very high compared to previous studies, reaching 100%, while the prevalence rate of PCV2 is only 80% and is limited to replacement gilts. This indicates the widespread nature of PCV3 in apparently healthy sow populations. Data on reproductive parameters collected and compared between PCV3-negative and positive sows also revealed detrimental impacts on the overall reproductive performance of the studied herds, indicating the unstable PCV3 sow herds in the studied populations. The damage in farms with PCV3 positive sows could reach 1.41% of total piglets born and approximately 250 USD per week for a farm with 2,400 sows. Besides, the high similarity of ORF2 nucleotide sequences of PCV3 in this study suggests genetic stability within tightly source-controlled swine populations. This raises the concept of studying a viral population with a shared common ancestor silently impacting the reproductive performance particularly in the naïve replacement gilts. In conclusion, this study provides the first assessment of PCV3's impact on the reproductive performance of large-scale farm systems, highlighting the need for a virus control strategy within swine populations in the absence of widespread commercial PCV3 vaccination.