| Classical swine fever (CSF) is an acute, febrile, highly contagious disease, whichis caused by classical swine fever virus (CSFV). The typical symptoms are multiple organ hemorrhage and necrosis caused by degeneration of small blood vessels. It is theserious diseases in the development of global pig industry for the widely epidemic, contagious, high mortality rate. Although legal immunity procedure of CSF has been enforced, the disease is still prevalent and shows a complicated epidemic situation. In particular, the mix infection or secondary infection of swine fever with porcine reproductive and respiratory syndrome, swine pseudorabies, porcine circovirus type2(PCV2),Mycoplasma hyopneumoniae, pleuropneumoniae and Haemophilus parasuis were detected usually. Recently, the phenomenon of piglets congenital infection, immune failure and sow persistent infection are observed frequently and show sporadic situation.Many regions have carried out a study of the molecular epidemiology for prevention and control in CSF, but the research data is deficient in Shanxi Province.In this study, serum of different age pigs from42large-scale farms of eight citiesin Shanxi (Taiyuan, Jincheng, Changzhi, Jinzhong, Yangquan, Luliang, Shuozhou,Xinzhou)，total1776samples, were collected and tested. The ELISA results showedthat: the average of CSF antibody positive rate is57.55%, averaged antibody positiverate of breastfeeding pig and nursery pig is70.11%and40.57%, respectively;averaged antibody positive rate of finishing pigs and sow is50.22%and69.69%,respectively. According to the result, we consider that swine fever antibody level inthe scale pig farm of Shanxi did not reach the optimal situation, especially the nurserypig.Then, the E2gene of five CSFV strains which were isolated from some areas ofShanxi recently were amplified by nested RT-PCR in2013, cloned and sequenced,respectively. The E2gene sequences of these five strains were analyzed and comparedwith the sequences that published CSFV strains by DNAStar, then, the phylogengtic tree of E2were constructed. The results showed that the homologies of nucleotide andamino acid sequences of the five strains were81.4%-100%and87.9%-100%,respectively; the homologies of nucleotide and amino acid sequences of the fivestrains to Shimen strain were82.9%-94.8%and89.0%-94.9%, respectively; thehomologies of nucleotide and amino acid sequences of the five strains to CSFVLapinised strain (HCLV) were81.6%-99.6%and87.9%-99.5%, respectively; thehomologies of nucleotide and amino acid sequences of the five strains to the17islolates from different regions of the world CSFV strains were81.5%-99.6%and86.3%-99.7%, respectively. The phylogenetic analysis showed that the four strainsbelonged to GroupⅡ, and variations of amino acids sites were observed at sites705,713,729and734; The other1strain belonged to group I. These results not only showthat the epidemic strains in shanxi province have diversity in genetic variation, butprovide a theoretical basis for the screening and development of classical swine fevervaccine and a scientific rational prevention of classical swine fever. |
