| Porcine reproductive and respiratory syndrome (PRRS) caused by Porcine reproductive and respiratory syndrome virus (PRRSV), is a serious infectious disease characterized by severe reproduction failure in sow and serious respiratory disturbance in piglets. PRRSV has restricted tropism for porcine alveolar macrophages and antigenicity variation, resulting in the variant strain in prevalence currently. The traditional commercial vaccines to prevent PRRS are mainly attenuated and inactivated vaccines. Attenuated vaccines can provide solid protection and have saftey against PRRSV, Compared with attenuated vaccine, inactived vaccine is safe, but its effect is not stable. Protection and saftey of attenuated vaccine were consented by pig-breeding industry.PRRS epidology investigation was carried from 108 scale pig-breeding farms in middle and lower reaches of Changjiang River of China.2459 serum samples were collected and detected for antibody by IDEXX PRRSV kit, statistics analysis of the detecting data of serum antibody was carried from defferent regions、age and year. The data indicated that positive ratio of PRRSV was 93.70%(2304/2459); positive ratio of PRRSV antibody is 91.1% in 2005; positive ratio of PRRSV antibody is 94.8% in 2006; positive ratio of PRRSV antibody is 96.1% in 2007, positive ratio of PRRSV antibody increased by year.Primers were designed and synthesized according to PRRSV genome sequence of Genbank. RT-PCR assay for PRRSV was established. PRRSV and other reproduction failure pathogen (PRV、CSFV、PCV-2、PPV及JEV) were detected for 127 sampes from Eastern of China. Only 10 of 127 (7.87%) samples was infected by PRRSV alone,95 (74.8%) samples was infected by PRRSV and PPV,50 samples was infected by PRRSV and PCV2,15 samples was infected by PRRSV and PRV,8 samples was infected by PRRSV and JEV,18 samples was infected by PRRSV and CSFV. It indicated that mix infection between PRRSV and PPV, PRV, PRRSV, PCV-2 was common.There was obvious disparity of nucleotide sequence from defferent PRRSV strain. PRRSV can be divied into two genotypes:Europen type (LV) and Northern American (ATCC VR-2332), nucleotide homology between two genotypes is about 60%. GP5、GP6(M) and GP7(N) by translated by PRRSV ORF5、ORF6、ORF7 respectively were primary structure protein. There was more disparity between ORF5 sequence of deffernet coutry and regions. Nucleotide sequence of thee structure protein of PRRSV isolates was analysised from defferent regions in middle and lower reaches of Changjiang River of China.and copared with VR-2332 and LV. The data indicated that the nucleotide sequence of PRRSV isalates ORF5 in middle and lower reaches of Changjiang River of China had 88.9%～90.2%、63.3%～64.2%、88.1%～89.4%、95%～96%、96.4%～97.2%、89.1%～90.9% homology with PRRSV VR-2332、LV、BJ-4、CH-la、HB-1 and WSV; amino acids sequence of PRRSV isalates ORF5 in middle and lower reaches of Changjiang River of China had 87.1%～90%、55.7%～57.2%、85.1%～88.1%、91.5%～94.5%、93.5%～96%、88.1%～90.0% homology with PRRSV VR-2332、LV、BJ-4、CH-la、HB-1 and WSV.It is difficut to control for obfuscation of PRRSV immune and immune inhitor, persisted infection of PRRSV. PRRS diagnosis assay was established in order to diagnosis PRRS accurately. A sires of measures including breed management, vaccination, control of fellow infection ang veterinary biology saefety were designed and apllied by pig-breeding farms of the Eastern of China. It indicated that reasonable vaccine procedure, accurate vaccination, strength safety measures, improved diagnosis level, control of fellow infection can degrade infectious and morbidity ratio and control prevalence ang widespread of PRRS to some extent for obvious economic and society advantage. |
PDF Full Text Request