Epidemiology and Evolutionary Characteristics of the Porcine Reproductive and Respiratory Syndrome Virus in China between 2006 and 2010

Abstract

In 2006, an emerging highly pathogenic strain of porcine reproductive and respiratory syndrome virus (PRRSV), which causes continuous high fever and a high proportion of deaths in vaccinated pigs of all ages, broke out in mainland China and spread rapidly to neighboring countries. To examine the epidemiology and evolutionary characteristics of Chinese PRRSV after the 2006 outbreak, we tested 2,981 clinical samples collected from 2006 to 2010 in China, determined 153 Nsp2 sequences and 249 ORF5 sequences, and analyzed the epidemiology and genetic diversity of Chinese PRRSV. Our results showed that the percentage of PRRSV-positive specimens collected from sick pigs averaged 60.85% in the past 5 years and that the highly pathogenic PRRSV has become the dominant strain in China. Furthermore, a reemerging strain which apparently evolved from the highly pathogenic PRRSV strain in 2006 appeared to be widely prevalent in China from 2009 onwards. Sequence analyses revealed that the hypervariable region of Nsp2 in most of the isolates contained a discontinuous deletion equivalent to 30 amino acids, along with other types of deletions. Extensive amino acid substitutions in the GP5 sequence translated from ORF5 were found, particularly in the potential neutralization epitope and the N-glycosylation sites. Our results suggest that Chinese PRRSV has undergone rapid evolution and can circumvent immune responses induced by currently used vaccines. Information from this study will help in understanding the evolutionary characteristics of Chinese PRRSV and assist ongoing efforts to develop and use PRRSV vaccines in the future.

Porcine reproductive and respiratory syndrome virus (PRRSV) from the first outbreak of India shows close relationship with the highly pathogenic variant of China

“…PRRS caused by HP-PRRSV also presents a serious swine disease characterized by high fever (40À42 C), high morbidity (50%À100%) and mortality (20%À100%) in all ages of pigs similar to the findings of the present study. HP-PRRS first emerged in Southern China in 2006 and subsequently spread throughout China, affecting more than 20 million pigs (Tian et al 2007;Li et al 2011). The HP-PRRS virus was observed to have a unique molecular hallmark of 30 amino acids deletion in non-structural protein 2 (Nsp2) (Zhou et al 2009).…”

Pathogenesis of nonsuppurative encephalitis caused by highly pathogenic Porcine reproductive and respiratory syndrome virus

“…This disease affected over 2,000,000 pigs and caused 400,000 fatal cases in more than 10 provinces. [6][7][8]13 The pigs infected by HP-PRRSV had the following atypical PRRS symptoms: neurological symptoms (e.g., shivering, lameness, and opisthotonus), high fever (40-42°C), and an erythematous blanching rash.…”

Complete Genome Sequence of an Overattenuated Highly Pathogenic Porcine Reproductive and Respiratory Syndrome Virus

“…Highly pathogenic PRRSV (HP-PRRSV) is a mutant of PRRSV containing a novel discontinuous 30-aminoacid (30-aa) deletion in nonstructural protein 2 (Nsp2) (7,12). HP-PRRSV is the etiological agent of HP-PRRS epidemics, which first emerged in southern China in 2006; the virus is currently widespread in China and several Southeast Asian countries, causing enormous economic losses (1,3,6,9,12). Live attenuated PRRSV vaccines based on serial in vitro passage are efficient tools that can be used to protect pigs against PRRSV infection (8,13).…”