Emergence of novel European genotype porcine reproductive and respiratory syndrome virus in mainland China

Abstract

Porcine reproductive and respiratory syndrome (PRRS) has a major negative economic impact on the swine industry worldwide. During the investigation of PRRS virus (PRRSV) in mainland China, European genotype (EU, type 1) PRRSV isolates were detected in swine herds both with and without clinical symptoms. Two complete genome sequences for Chinese type 1 PRRSV isolates were identified from viruses isolated from lung tissue and sera. The two viruses, designated BJEU06-1 and NMEU09-1, produced cytopathic effects in primary porcine alveolar macrophages but not in Marc-145 cells, and had a mean diameter of 55 nm, as measured by transmission electron microscopy . Comparative sequence analysis revealed that they shared 87.0-91.5 % and 58.0-58.2 % identity with the EU and North American genotype (NA, type 2) prototypic strains LV and VR-2332, respectively. Remarkably, these isolates, characterized by concomitant deletions within non-structural protein 2 (Nsp2) and ORF3 hypervariable regions, have never been described. Phylogenetic trees showed that all of the novel Chinese isolates of European genotype are in the pan-European subtype 1 that is predominant in Europe. However, they evolved from different ancestors. These novel viruses are predicted to be products of the divergent evolution of ancestor PRRSV isolates introduced from Europe. This is the first report of type 1 PRRSV wild isolates being in mainland China. Our findings confirm that the Chinese type 1 PRRSV isolates originated from diverse progenitors and the type 1 and type 2 PRRSV isolates, having different biological properties, have coexisted on the Chinese mainland for several years. INTRODUCTIONPorcine reproductive and respiratory syndrome (PRRS) emerged in North America in 1987(Keffaber, 1989 and in western Europe in 1990(Wensvoort et al., 1991, and is now one of the most economically significant swine diseases worldwide. The aetiological agent of the disease, PRRS virus (PRRSV), was isolated in the Netherlands in 1991 (Wensvoort et al., 1991) and subsequently in the United States (Collins et al., 1992). Even though the PRRSV isolates on the two continents emerged almost simultaneously, caused similar disease symptoms and shared the same virion morphology, European and North American PRRSV isolates were antigenically and genetically very different (Forsberg et al., 2002;Ropp et al., 2004;Rossow, 1998). Thus, two genotypes of PRRSV have been defined: the European (EU genotype, type 1) and the North American (NA genotype, type 2) strains (Meng et al., 1995;Nelsen et al., 1999). Originally, EU PRRSV was restricted to Europe, while NA PRRSV was restricted to North America and Asia. Nowadays however, coexistence of the two genotypes has been identified in Europe, North America and Asia, complicating PRRSV differential diagnosis, disease prevention and control (Amonsin et al., 2009; Balka et al., 2008;Bøtner et al., 1997;Dewey et al., 2000; Fang et al., 2007;Kim et al., 2009b;Ropp et al., 2004; Thanawongnuwech et al., 2004;van Vugt et al., 2001).PRRSV is an en...

Pathogenesis of Korean Type 1 (European Genotype) Porcine Reproductive and Respiratory Syndrome Virus in Experimentally Infected Pigs

“…The results of this study confirm that Korean type 1 PRRSV is able to induce clinical signs and gross and microscopical lung lesions, as is Korean type 2 PRRSV. Recently, type 1 PRRSV has emerged in Asian countries, including China and Thailand (Thanawongnuwech et al, 2004;Amonsin et al, 2009;Chen et al, 2011). Further studies are required to control the economic loss from this emerging type 1 PRRSV.…”

Porcine reproductive and respiratory syndrome virus

“…7,25,32 Atypically diverse EU genotype PRRSV strains have been reported in several European countries, 18 for instance in Denmark, 24 Spain, 7 Germany, and the Netherlands, 25 as well as in Italy. 9 The global dissemination of pan-European subtype 1 is assumed, as strains classified into this subtype have been recently reported in Asian countries such as China, 5 Korea, 21 and Thailand. 37 Subtypes 2, 3, and 4, whose existence was solely reported from Eastern Europe so far, exceed the diversity of subtype 1.…”

Genomic characterization and pathogenicity of a strain of type 1 porcine reproductive and respiratory syndrome virus

“…Although type 1 PRRSV has been recognized in recent years (Chen et al, 2011;Zhou et al, 2015b), information relevant to genomic molecular characterization and pathogenicity of type 1 PRRSV remains limited in China. In the present study, we characterized an isolate of type 1 PRRSV from the serum samples of a pig farm with clinically respiratory symptoms of PRRS, and analyzed the genomic genetic variation of the virus and its pathogenicity for piglets.…”