| Abtract:Classical swine fever (CSF) is an acute porcine infections disease which is caused by classical swine fever virus (Classical swine fever virus, CSFV). The world organization for animal health (OIE) put swine fever as a major animal epidemic must reported. CSFV is a member of the Flavivirus genus Parvovirus, oval form of the virus, with the capsule, about 40-60nm in diameter, have a single-strand RNA virus, viral nucleic acid about 12,300 nucleotides in length, contains a large open reading frame coding 3,898 amino acid precursor protein. The precursor protein in the process of synthesis is decorated virus itself coding, hydrolysis eventually to four structural protein and eight non-structure protein, The order of the viral protein (from N to terminal C):Npro、C、Ems、E1、E2、P7、NS2、NS3、NS4A、NS4B、NS5A and NS5B, C, Erns, El and E2 are protein structure, other are not structural proteins.. Pig is the only animal susceptibility of CSFV and the spread of the virus host, all of ages pigs can be infected. Among all the pig diseases, swine fever is one of the most serious infectious disease, cause serious economic losses to China’s pig industry. Since the second half of 2014, The Shandong province, Jilin province, Heilongjiang province, Hebei provinces of China according to the normal immune swine fever rabbit weak poison vaccine of CSFV the outbreak of large-scale pig farms are still, caused huge losses to the pig industry. Since the second half of 2014, Shandong province, Jilin province, Heilongjiang province, Hebei provinces according to the normal immune swine fever rabbit weak poison vaccine of CSFV the outbreak of large-scale pig farms are still, caused huge losses to the pig industry. Pig is the only susceptibility animal of swine fever virus, wild boar pigs can be infected, and the pig is the only spread swine fever virus host, all sorts of day age pigs can be infected with swine fever virus. Cattle sometimes infected with classical swine fever virus, but the cattle infected with classical swine fever virus not show obvious symptoms. Swine fever outbreak and epidemic does not have a specific season and no obvious geographical feature. As long as there are risk of pigs, once swine fever virus introduced, can cause the outbreak of swine fever and popular. Pigs mainly through semen, urine, feces and nasal secretions to detoxify. CSFV susceptible host is wild boars,because wild boar in the global, distribution swine fever virus easily the chain to form the spread of the virus in wild boar. Swine fever is one of the major pig disease which have serious damage to the pig industry in our country, since the 1950 s, China successfully developed the rabbit weak poison vaccine, the vaccine is widely spread and applied to today, effectively suppress the outbreak of swine fever and widely popular. In 1956, our country put forward to eradicate swine fever based on the rabbit, weak poison vaccine,60 years on, however, swine fever in uninterrupted, yet popular in our country, still endangering China’s pig industry. At present, the popularity of swine fever has the following characteristics; (1) widespread, swine fever in each region are popular in our country, Chang-chun tu in 31 provinces (autonomous regions and municipalities directly under the central government) material, the collection of clinical disease were detected swine fever, thus it can be seen swine fever is the extent of popular in our country. (2) Swine fever sends out popular in our country,.Because the rabbit weak poison vaccine widely promotion and use of, our country pigs have certain immune ability to swine fever virus, so the plant blast no large-scale outbreak and popular in our country. The popular trend of swine fever in our country is sending out, low intensity, no obvious seasonal. (3) The onset age, The onset of China pig more is under 3 months, especially before and after weaning piglets. Into a lower incidence of swine. (4) Disease complex, Swine fever has been around for years in our country, is the most common clinical disease in our country. (5) Low immunity, Although our country has established the mechanism of the immune system, each department and the pig immune prevention of swine fever also attaches great importance to by the owners, but swine fever virus, and in the process of popular rabbit weak poison vaccine immunization effect decrease.Most major epidemic of swine fever virus in China is 2.1 b subtype, Swine fever virus evolve with the passage of time.2014 tested swine fever in our country some after strict immune pig, after the virus isolation, identification and phylogenetic tree analysis, the results show that our country swine fever epidemic situation has changed. In order to further understand the prevalence of CSFV and molecular characteristics, In this study, we separate strains of CSFV variant and measure and analyzethe E2 gene sequence, and analysis the whole genome sequencing of variant. (1) The determination and analysis of CSFV E2 gene sequences, In this study, tested suspected CSF disease samples by RT-PCR method, which from the four provinces In the second half of 2014.there are 14 samples in CSFV positive among the 28 tissue samples. Test the 14 samples E2, genome sequencing and analysis. Results showed that the 11/14 CSFVs in 2015 belonged to the 2.1d subgenotype, and 3/14 belonged to the 2.1b subgenotype. Furthermore, compared with the shimen, HCLV,2.1b subgenotype, the nucleotides similarity of 11 new CSFVs were 82.8～84.1%,81.1～82.4%,92.6～97.1%, respectively, and the amino acids similarity were 89.8～91.2%,88.2～89.8%,94.1～98.9% respectively. In addition,2.1d subgenotype was of the same molecular characteristics, which were R31, S34, K303 and A331 in E2 gene.(2) The isolates SDSG1410 and SDLS1410 genome research, two CSFVs named SDSG1410 and SDLS1410 isolated from Shandong area were sequenced with six pairs of primers based on zj0801 strain of CSFV. Both genomic RNA of the CSFVs were 12,296 nt in length. Phylogenetic analysis indicated that two CSFVs were classified into 2.1d subgenotype CSFV in compareing with the full viral genomic sequences, which was consistent with the result based on the E2 gene. Then, the nucleotides and the deduced amino acid similarity showed the genome similarity of the two virus, compared with zj0801,Shimen and HCLV, were 97.3%-97.5%,85.0%-85.1% and 84.3%-84.4%, respectively. In addition, the high sequence variations were found in Npro, C, E2, NS2, NS5A, and 3’UTR regions. Furthermore, the full genome of new 2.1d subgenotype shared several consistent molecular characteristics such as V640, K992, A1020, M1090, R1395 and D2374 in encoding sequence of the virus.E2 whole genome sequence analysis showed that 2.1 d subtype strains has become a major epidemic strain of CSFV in our country. SDSG1410 and SDLS1410 whole genome sequence analysis also shows the same result, Consistent with our 2014 CSFV epidemiological study. This study on the whole genome level of our country popular CSFV nucleotide and amino acid analysis, The results showed that 2.1 d subtypes strains has been popular in our country, The subtype strains has been in weak poison has rabbit immune scale pig farms, weak poison vaccine cannot fully protect that rabbit. This study illustrates the 2.1 d strains from the molecular level has been widely popular in our country, promote the molecular characteristics of the strain of 2.1 d in understanding, as well as CSFV prevention and control strategy, the development of new vaccine provides an important scientific basis. |
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