Longitudinal Monitoring of Mono- and Coinfections Involving Primary Porcine Reproductive Viruses (PCV2, PPV1, and PRRSV) as Well as Emerging Viruses (PCV3, PCV4, and nPPVs) in Primiparous and Multiparous Sows and Their Litters

Porcine reproductive failure (PRF) has multiple etiological origins, primarily involving the viruses PCV2, PPV1, and PRRSV. Some emerging viruses, such as PCV3, PCV4, and novel parvoviruses (nPPVs), have also been suggested as contributors. In this study, we longitudinally evaluated 40 healthy sows (20 gilts and 20 multiparous sows) over three phases: pregnancy (PP), farrowing (FP), and their litters during lactation (LP). We detected viruses through PCR and serology in mono- and coinfections. The results showed that primary viruses were present during all three phases, with PCV2 being the most frequently detected. PCV3 positivity was highest at the time of insemination, and PPV1 was found in all. Additionally, PPV1-positive fetuses and pre-suckling piglets were identified, indicating vertical transmission. PRRSV was also present in an unstable herd, with the PRRSV2 lineage A detected and evidence of vertical transmission. The majority of coinfections were either dual or triple. The most common coinfections in the PP and LP were PCV2/PPV1 and PCV2/PCV3, while in the FF, PCV2/PPV1 and PCV2/PRRSV predominated. Notably, coinfection PCV2/PPV1 impacted the replication of PCV2. In contrast, the likelihood of detecting PRRSV decreased in fetuses coinfected with PRRSV and either PCV2, PCV3, or PPV1. The detected viruses exhibited low viral loads, indicating subclinical infections. Therefore, we propose recognizing a subclinical presentation of PRF and establishing criteria to differentiate between this and symptomatic reproductive disease.