Synergistic Pathogenicity by Coinfection and Sequential Infection with NADC30-like PRRSV and PCV2 in Post-Weaned Pigs

Abstract

Porcine reproductive and respiratory syndrome virus (PRRSV) and porcine circovirus (PCVs) are two major viruses that affect pigs. Coinfections between PRRSV and PCV2 are frequently reported in most outbreaks, with clinical presentations involving dyspnea, fever, reduced feed intake, weight loss, and death in fattening pigs. The NADC30-like PRRSV and PCV2d are the main circulating virus strains found in China. This study determines the impact of NADC30-like PRRSV and PCV2d mono-infection and coinfection on the immune system, organ pathology, and viral shedding in five-week-old post-weaned pigs. Pigs were randomly divided into six groups: PBS, PRRSV, PCV2, PRRSV-PCV2 coinfection (co), and PRRSV-PCV2 or PCV2-PRRSV sequential infections. Fever, dyspnea, decreased feed intake, weight loss, and pig deaths occurred in groups infected with PRRSV, Co-PRRSV-PCV2, and PRRSV-PCV2. The viral load was higher in Co-PRRSV-PCV2, PRRSV-PCV2, and PCV2-PRRSV than those mono-infected with PRRSV or PCV2. Additionally, cytokines (IFN-γ, TNF-α, IL-4, and IL-10) produced by pigs under Co-PRRSV-PCV2 and PRRSV-PCV2 groups were more intense than the other groups. Necropsy findings showed hemorrhage, emphysema, and pulmonary adhesions in the lungs of pigs infected with PRRSV. Smaller alveoli and widened lung interstitium were found in the Co-PRRSV-PCV2 and PRRSV-PCV2 groups. In conclusion, PRRSV and PCV2 coinfection and sequential infection significantly increased viral pathogenicity and cytokine responses, resulting in severe clinical signs, lung pathology, and death.

Immune Molecules’ mRNA Expression in Porcine Alveolar Macrophages Co-Infected with Porcine Reproductive and Respiratory Syndrome Virus and Porcine Circovirus Type 2

“…Previous studies on the effects of co-infection of PRRSV and PCV2 on pigs had different findings. Jinyong Zhang et al, found that the serum concentrations of IFN-γ in pigs co-infected with PRRSV and PCV2 were significantly higher than those in the control group [ 53 ]. Peihu Fan’ team discovered that the HP-PRRSV/PCV2 co-infection group had up-regulated serum concentrations of TNF-α and IL-10, while IFN-γ was lower in the co-infection groups, especially the HP-PRRSV/PCV2 group, than in the single-infection groups [ 16 ].…”

Canine Circovirus Suppresses the Type I Interferon Response and Protein Expression but Promotes CPV-2 Replication

“…Coinfection of PCV2 or PCV3 with PPV leads to severe viremia and reproductive disorders [ 33 , 34 , 35 ]. In addition, PCV-2 infection inhibits the response of immune-related signaling pathways and promotes the replication of viruses such as pseudorabies virus and porcine reproductive and respiratory syndrome virus [ 36 , 37 ]. Worse still, duck circovirus also causes immunosuppression, and coinfection with other pathogens can lead to serious consequences [ 38 , 39 ].…”

Prevalence of porcine circovirus type 2 and type 3 in slaughtered pigs and wild boars in Korea

“…Other Korean research teams have demonstrated that positive rates of PCV3 in whole blood, serum, and nasal swabs (Dhandapani et al, 2021) and whole blood (Song et al, 2021) samples of wild boars were 5.6% and 0.01 %, respectively. Although we cannot rule out the possibility of other influences, these rapidly increasing positive rates of PCV3 in this study might be due to sample differences (Kixmöller et al, 2008;J. Zhang et al, 2022).…”