Molecular Investigation of Porcine Circovirus 2, Porcine Circovirus 3, Porcine Circovirus 4, and Porcine Parvovirus in Clinical Samples from Brazilian Swine Herds

Porcine circoviruses (PCV2, PCV3, and PCV4) and porcine parvovirus (PPV) are important viral pathogens associated with respiratory, enteric, and reproductive disorders in swine. This study investigated the molecular occurrence of PCV2, PCV3, PCV4, and PPV in samples from an Influenza A virus epidemiological study and from routine diagnostic submissions to a reference animal virology laboratory in Brazil. A total of 358 clinical samples collected between 2023 and 2025 from commercial swine herds in six Brazilian states were analyzed, including fetal tissues, piglet tissues, and nasal and rectal swabs. PCV2, PCV3, and PCV4 were detected by real-time PCR, whereas PPV was investigated by nested PCR. In the epidemiological study, PCV3 and PCV2 were detected in 17.3% and 13.3% of samples, respectively, with co-detections involving Influenza A virus. In routine diagnostic samples, PCV2 was most frequently detected in finishing pigs and piglet tissues, while PCV3 predominated in farrowing-phase samples and piglet tissues. PPV was detected exclusively in fetal tissues (19.1%). PCV2 detection significantly decreased over time, whereas PCV3 increased significantly. PCV4 was not detected. These findings confirm the circulation of PCV2, PCV3, and PPV and support continued molecular surveillance in Brazilian swine herds.