The Investigation And Research Of Province Of Porcine Reproductive And Respiratory Syndrome In Some Farms Of Anhui Province

Porcine reproductive and respiratory syndrome (PRRS) is a highly contagious infectious diseases, which caused by porcine reproductive and respiratory syndrome virus (PRRSV). The main features of PRRS are reproductive barriers in sow and respiratory disease in piglets. PRRS were prevalent in almost all countries and obstruct the development of the pig farming industry seriously.In the past few years, there were some infectious disease happened in some forms of Anhui province during the July to October, with repeated fever and symptoms of the respiratory tract. Respiratory symptoms are also significant features of PRRS, which could occur in the most stage of pig production cycle. In order to know the prevalence of PRRS in Anhui province, some farms without PRRSV vaccination were chosen for detection of the virus antibodies using an indirect ELISA method. Three hundred and seventy seven serum samples were detected, while 121 samples showed positive. The positive rates were 32.1%. The results showed that there were natural infection of PRRSV in these farms. The relationships between incidence of the infection and the age, species and geographical distribution of pigs were also analyzed in this study.According to the nucleocapsid protein gene (N gene) of the Inter-American-type PRRSV strain (ATCCVR-2332), PCR primers were designed to detect 51 clinical samples collected from Hefei, Anqing, Lu'an, Huaibei and Maanshan in Anhui province during 2006.06 ~ 2008.07. thirty seven samples showed positive results, the detection rate was 72.5%. The positive samples were chosen to detect the mutants using Nsp2 (1594～1680) RT-PCR detection kit bought from IDEXX company. The results showed that 22 were positive, with a detection rate of 59.5%. These results showed that the detection rates of PRRS in the five areas were high, and most of the virus were mutants.According to the Genbank which have published about PRRSV strains ORF5 gene sequences, design a pair of specific primers for six of the mutant gene amplification for ORF5. for which the amplification of 603bp fragmentPCR primers were designed according to the PRRSV ORF5 reference gene sequences from Genbank. Six mutant strains were used as templates, and the amplified DNA product named AH / MAS, AH / HF, AH / CZ, AH / WH, AH / TC, AH / HN, respectly were cloned into pMD18-T vector , transformed into E. coli DH5αand sequenced. These sequences were compared with the ORF5 gene of vaccine strains (JXA1), isolated from the domestic (CH-1a, SX-1603, HB-4), two American strains (PRRSV0000003158 , PRSV0000003748), a European strain (EuroPRRSV) and a Korean strain (PL97-1LP1WSV) using DNAStar software. The results showed that These six PRRSV mutants strains belonged the North America type, and beloned to two different subgroups. The similarities between the six DNA sequences ranged from 86.1% to 99.3%; the similarities between these six sequence and the United States strains ranged from 88.4%to 94.4%; the similarities were from 86.1% to 99.3% when compared with strains of South Korea; the similarities ranged from 85.7% to 99.8% compared to the isolates from other provinces of China; the similarities ranged from 60.0% to 63.8% when compared with the European strains.Analysis of the antigenic epitope of these six mutants' GP5 protein showed that there were antigenic variation between these strains.In conclusion, the PRRSV could be detected in some farms of Anhui province through different methods, such as serological antibody detection and RT-PCR detection of virus RNA. These studies have confirmed the prevailing of PRRS in Anhui province.Characteristic of easy variation of the PRRSV has been the main concern of researchers. PRRSV ORF5 in different geographical homology analysis showed that the strains from Anhui sequencing largely difference from each other . Which clear that in recent years, a source of PRRSV Anhui region, molecular evolution and genetic characteristics of great significance. Analysis of the characteristics of epidemic strains in Anhui Province and the current strain of PRRSV whether have a certain relationship. At the same time, the ORF5 gene of PRRSV variability GP5 protein research and comparative analysis of the antigenicity, which for the future direction of vaccine provides a theoretical reference.