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

Jinyong Zhang,He Zhang,Peng Wang,Zhuoxin Li,Huijun Lu,Changzhan Xie,Yubiao Xie,Xiangshu Qiu,Ningyi Jin,Ning Shi,Zhuo Ha,Yimo Tao,Jicheng Han

doi:10.3390/v14020193

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.

Highlights

Porcine reproductive and respiratory syndrome (PRRS) is an infectious disease with a high infectivity rate in pigs
Rectal temperatures of Porcine Reproductive and Respiratory Syndrome virus (PRRSV), PRRSV-porcine circovirus 2 (PCV2), and Co-PRRSV-PCV2 groups increased significantly on the 4th dpi, in which a high rectal temperature lasted for about six days
According to the results of symptoms scoring, the clinical signs of PRRSV-PCV2, Co-PRRSV-PCV2, and PCV2-PRRSV infected groups were more severe than the other groups (Figure 1B)

Summary

Introduction

Porcine reproductive and respiratory syndrome (PRRS) is an infectious disease with a high infectivity rate in pigs. It is caused by the Porcine Reproductive and Respiratory Syndrome virus (PRRSV), an enveloped RNA virus in the genus Arterivirus of the family Arteriviridae [1]. In China, PRRSV was first reported in 1996 [6]; and a new PRRSV characterized by high morbidity and mortality, named highly pathogenic PRRSV (HP-PRRSV), emerged in 2006 [7]. The NADC30-like PRRSV strain was first detected in 2013 This novel strain spread rapidly and soon became one of the most predominant circulating PRRSV strains in the domestic pig industry, causing substantial economic losses [8,9]. The NADC30-like PRRSV showed much lower pathogenicity as compared with HP-PRRSV [12]

Methods

Results

Conclusion