Abstract
Porcine reproductive and respiratory syndrome virus (PRRSV) has been epidemic more than 30 years in America and 20 years in China. It is still one of the most important causative agents to the worldwide swine industry. Here, we systematically analyzed the prevalence status of PRRSV in China by a molecular epidemiological perspective. Now both PRRSV-1 and PRRSV-2 are circulating and approximately more than 80% of pig farms are seropositive for PRRSV. For PRRSV-2, there are four lineages (lineage 1, lineage 3, lineage 5, lineage 8) circulating in the fields. Lineage 8 (CH-1a-like) and lineage 5 (BJ-4-like) appeared almost at the same time during 1995-1996. Notably, BJ-4 shares 99.6% and 99.8% identity with VR2332 and RespPRRS MLV, respectively. It means that lineage 5 is likely to be imported from America. Now highly pathogenic PRRSV (HP-PRRSV) which was considered to be evolved from local diversity of lineage 8 strains is predominant with different variants. Lineage 3 appeared in 2010 which is mainly sporadic in south of China. Lineage 1, also known as NADC30-like strains in China, has been prevalent since 2013 and leads to PRRS pandemic again. For PRRSV-1, although sporadic at present, more than 9 provinces/regions have been reported. All the circulating strains belong to subtype I. It should be paid more attention since there are no vaccines available. Our analysis would help to deeply understand the prevalent status of PRRSV in China and provide useful information for prevention and control of porcine reproductive and respiratory syndrome (PRRS).
Highlights
Porcine reproductive and respiratory syndrome (PRRS) is one of the most important economically diseases to the swine industry worldwide
Highly pathogenic Porcine reproductive and respiratory syndrome virus (PRRSV) (HP-PRRSV) which was considered to be evolved from local diversity of lineage 8 strains is predominant with different variants
Serological studies showed that the percent of positive serum is more than 40% in the east and north of China [30], and it means that PRRSV circulated in China earlier than 1995
Summary
Porcine reproductive and respiratory syndrome (PRRS) is one of the most important economically diseases to the swine industry worldwide. The reason for this re-pandemic of PRRS is considered as the emergence of NADC30-like strains which were probably imported from North America and went though extensive variation in China [24, 25, 35] Both HP-PRRSV-like and NADC30-like strains are mainly circulating in the fields and have a high clinical detection rate. Genetic variation The genome homology between Chinese isolated strains and Lelystad virus ranges from 85.9% to 92.7%, and the similarity of ORF5 with Lelystad virus is about 83.5~94.6% except the B13 which shows 99.7%, only two nucleotides different from Lelystad virus It suggests that B13 may be isolated from import breeding pigs or as a standard reference strain from some western European countries. These vaccines are effective in reducing clinical signs, decreasing viremia and
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