| Pseudorabies is caused by pseudorabies virus,which is characterized by highly contagious and infectious.A variety of domestic and wild animals can be infected with this disease,while the main symptoms are fever,itching(except pig)and encephalomyelitis et al.Pigs can be infected by PRV at different growth stages,which lead to abortion,stillbirths and mummified.Infected piglets have the neurological symptoms and eventually death,with a death rate of nearly 100%.Liu Yongchun isolated the PRV from cats at 1947,which showed the presence of Pseudorabies virus in China.Up to now,it has been continuously reported in more than 20 provinces and cities.However,since the autumn of 2013,the farms vaccined(g E-)by the deficiency PRV showed a suspected PR case in Henan,Jilin,Heilongjiang and other regions.Therefore,our work investigated and analyzed the epidemic of pseudorabies in parts of Henan province by PCR.We isolated and identified some PRV strains in Henan province.Additionally,we cloned the full length of the genes g E and g C,as well as perfomred the preliminary research on them.From August 2013 to April 2015,we analyzed 308 suspected cases from 74 pig farms by PCR,with the positive rate of 27.8% and the positive of pig farms of 54%.We also analyzed the positive rate in different regions of Henan province.The highest was Middle Henan,40.1%;the South Henan was lowest,17.3%;while the positive rate of East Henan,West Henan and North Henan were 25.6%,24.5% and 30.2%,respectively.Additionally,we analyzed the PR positive rate of farms in different regions.The North Henan was highest,66.7%;the South Henan was lowest,41.7%;while the West,East and Middle were 56.5%,54.4% and 57.9%,respectively.Besides,we Analyzed the samples at different times,the positive rate from Oct to Nov 2014 was highest,36.1%;the positive rate from Aug to Oct 2013 was lowest,16.6%.We also analyzed the samples in different season,the positive rate of spring and winter were higher,0.9% and 28.9%,respectively.The positive rate of summer and autumn were lower,22.9% and 27%,respectively.We inoculated the positive samples into the swine testicular(ST)cells,by which we obtained 6 strains of PRV,which were named YZ,SMX,BP,WZ,WY and YY,respectively.These 6 strains showed stable CPE on ST cells,and they can also amplified the specific g E gene sequence with a 429 bp.Proliferated by 7 generations,the virulence titer of these 6 strains reached to 10-5.6 ~ 10-8.These 6 PRV strains were inoculated into the six weeks female mice,which led to the death.Referring the g E gene sequence(AF171937)published in Gen Bank,one pair of primers were designed by Primer5.0.The full length of g E genes of the seven wild PRV strains were amplified and cloned to p MD?19-T vector.Then,their sequences and evolutionary features were analyzed.These results showed that the nucleotide homology between the seven strains reached to 99.8% ~ 100%,among which the homology of BP and JZ,SMX and WY were100%,while the others between 99.8% and 99.9%.By the same method,referring the g C gene sequence published in Gen Bank,one pair of primers were designed by Primer5.0.The full length of g C genes of the seven wild PRV strains were amplified.The nucleotide homology between the seven strains was 99.4%~99.8%,whereas the other referred strains from domestic and abroad was 92.5%~100%.Among them,the strains YY YZ and JZ had the highest homology of 99.8%,whereas JZ,SMX and WY,three strains that had a lower homology with BP and WZ,which was 99.4%. |
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