The Synergic Role of Emerging and Endemic Swine Virus in the Porcine Respiratory Disease Complex: Pathological and Biomolecular Analysis

SIMPLE SUMMARY: Porcine respiratory disease complex (PRDC) represents a significant source of economic losses to pig farmers and swine industry worldwide, due to reduced growth, increased treatment costs and mortality rate. This disease complex is caused by various pathogens, including viruses such as PRRSV, PCV2, and bacteria such as M. hyopneumoniae. Co-infections of multiple agents, including emerging viruses such as TTSuV, PCV3, and PPV2, have been reported. These emerging viruses have been associated with lung lesions in pigs affected by PRDC. To investigate the presence of these agents, a study was conducted on swine lungs from different age groups. Histopathological examination and molecular tests were performed to identify involved agents. Results confirmed the presence of PPV2, TTSuV, and other viruses in affected pigs and revealed differences among swine age groups. The research provides valuable insights into PRDC’s complexity and highlights the importance of early detection and multidisciplinary approaches to effectively manage the disease in the intensive pig farming system. ABSTRACT: Porcine respiratory disease complex (PRDC) represents a significant threat to the swine industry, causing economic losses in pigs worldwide. Recently, beyond the endemic viruses PRRSV and PCV2, emerging viruses such as TTSuV, PCV3, and PPV2, have been associated with PRDC, but their role remains unclear. This study investigates the presence of PCV2 and PRRSV and emerging viruses (PCV3, TTSuV, and PPV2) in the lungs of swine belonging to different age groups by histopathology and real-time PCR. The prevalent lung lesion was interstitial pneumonia with increased severity in post-weaning pigs. PRRSV was detected in 33% of piglets’ lungs and in 20% of adults and post-weaning pigs with high Ct, while PCV2 was found in 100% of adult pigs, 33% of post-weaning pigs, and 22% of piglets, with low Ct in post-weaning pigs. PCV3 was present in all categories and coexisted with other viruses. TTSuV was detected in all swine in combination with other viruses, possibly influencing the disease dynamics, while PPV2 was detected in 100% of adults’ and 90% of piglets’ lungs. The detection of TTSuV, PCV3, and PPV2 in affected pigs prioritizes the need for comprehensive approaches in implementing appropriate control measures and minimizing economic losses associated with PRDC.