| Porcine reproductive and respiratory syndrome(PRRS),also known as “blue ear disease”,is currently one of the most infectious diseases cause huge economic loses to the world pig industry.At the end of 1995,China was first reported the occurrence of the disease,then spread across the country rapidly.It was cause irreparable economic losses.In 2006,there was a mysterious high fever of pigs in China,which was caused by the mutation of the mutation of the pathogen of the PRRS.In the late 1990 s,there was a lineage 3 PRRSV strain in Hong Kong,Taiwan,China.After 2000,it gradually spread from China's coastal areas to inland areas,causing a low fatality rate of pigs.In 2013,a new strain of the disease,NADC30-like,caused a new round of cases of the disease.PRRSV in China most of the pig present normalized to dye,in order to analysis of pig farms,the prevalence of PRRSV and major epidemic strain,select a pig farms in guangdong province to detect its dead pig group,2012-2015 during the tested a total of 219 suspected disease,found that the PRRS positive rate reached 42.5%.And the material from the positive disease won 9 strains of PRRSV strains,analysis of its genetic variability ORF5 and protein Nsp2,homology analysis results show that the obtained strain ORF5 gene sequence compared with American type VR2332 representative strains,homology between 83.4% and 89.6%;The homologous similarity with Chinese classical isolates CH-1a reached 86.4%-95.4%.Compared with the HP-PRRSV,a highly pathogenic PRRS outbreak in China in 2006,the homologous similarity was between 84.9% and 99.0%;Compared with the GM2 which is the representative of lineage 3 appeared in 2011,homology was between 82.9% and 96.2%;The homologous similarity was only 82.4% to 84.9% compared with the representative strain of the NADC30 strains,which was more popular in recent years.Compares about the Nsp2 encoding amino acid analysis,found that there are 4 strains in 9 strains sequence consistent with HP-PRRSV discontinuous 30 amino acids is missing,and another 5 strains have no same lack.The 9 strains can be divided into two lineages,there are 7 stains belong lineage 8,the other 2 stains belong lineage 3.The prevalence of PRRSV in this pig farm is similar to that of PRRSV in South of China,which can be used to predict the PRRS prevalence in this field.PRRS appeared in 2016,for the amateur breeding environment and whole pig disease,and for the amateur appeared dead pigs for autopsy,collecting dead animal tissue samples,test the PRRSV.Again to obtain tissue samples of 177,of which the positive rate of 89.3%,after the ORF5 from positive samples of amino acid sequence analysis found that the cause of the infection of PRRS strain and is very similar to previous pandemic strain,one is before and the belongs to the HP-PRRSV strains of subgroup JXA1 98.8% homology of strain,and another is 99.8% homology of GM2 strain.Against the epidemic,the pig formulation is given priority to with vaccine combined with keep the group of comprehensive prevention and control measures:(1)the whole all the pigs in 2 days using Ingelvac PRRS MLV emergency immunization;(2)keeping the grown group and weed out the pigs which was infested for three months;(3)to inoculate the piglet with streptococcus suis,and control bacterial infection;(4)strengthen biosafety control measures to reduce the circulation of the virus in the field;(5)insist on self-cultivation.Through above comprehensive prevention and control measures,starting from the onset in February 2016,farrowing rate declining from 86.9% before the onset of five month return to base production levels,tire number born qualified and doesn't seed ratio continuously affected six months back to base production levels.The monthly survival rate of piglet was recovered to the baseline production level in 4 months.The survival rate of the weaner was recovered to the baseline production level in 7 months.The survival rate of finisher was recovered to the baseline production level in the process of prevention and control in 5 months. |
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