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Surveillance And Genetic Evolution Analysis Of Newcastle Disease Around Dongting Lake Region

Posted on:2016-08-20Degree:MasterType:Thesis
Country:ChinaCandidate:W GuoFull Text:PDF
GTID:2283330485976615Subject:Preventive Veterinary Medicine
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The highly lethal characteristics of Newcastle disease (ND) causes serious damage to the breeding production of countries worldwide. With the policy of vaccine immunization carrying out in developing countries, the ND epidemic is controlled to some extend by wide application of vaccine. However, the trend of the spread of ND and the genotype of the current epidemic viral strain is constantly changing, and its host range is expanding, atypical ND is becoming more common. The research on molecular epidemiology of NDV is significant to evaluate the epidemical characteristics and local transmission of NDV.In order to investigate the distribution of NDV in the circum-Dongting Lake Region, through pathogen the sampling and monitoring of NDV in the region from 2013 to 2014. According to the serological identification,51 strains of NDV were isolated from embryonated eggs, including 34 chicken-origin strains,2 duck-origin strains and 15 environment-origin strains. Choosing 16 representative strains from different times, places and hosts, the F gene and HN gene were amplified by RT-PCR. The products were cloned into PMD18- T Easy Vector after purification, then sequenced and compared with the reference sequences published so far in Genbank. The phylogenic analysis indicated that one of the NDV isolates belongs to Class II genetype II, the amino acid sequence of the cleavage site of F protein is 112GRQGRL117, it’s a vaccine strain. The rest are all belong to Class I genetype 3, the amino acid sequence of the cleavage site of F protein is 112GRQGRL117. There is more than 97.8% homology to F protein and more than 98.2% homology to HN protein among the Class I strains that shows more closer genetic relationship to wild-bird Jilin strain J36/13.A total of 48 strains of NDV (32 chicken-origin strains,4 duck-origin strains,1 pigeon-origin strains and 11 environment-origin strains) were isolated from Live Bird Markets around the Dongting Lake Region. After sequenced and analyzed, these strains belong to Class Ⅰ and Class Ⅱ.41 strains of them are Class I genetype 3, the sample isolation rate and the total isolation rate of these strains are 3.66% and 85.42%.7 strains of them are Class II,1 genetype Ⅰ,5 genetype Ⅱ and 1 genetype VI, the sample isolation rate and the total isolation rate of these strains are 0.62% and 14.58%. it’s reported that the attenuated strains such as Class I are from waterfowl. Among all the strains Class I strains in this research, 75.6%(31/41) from chicken and 2.4%(1/41) from duck,and they are 97.4% homological to wild-bird Jilin strain J36/13. It’s indicated that these types of Class I strains may transmit between waterfowl, poultry and wildfowl.The high infection rate of Class I strain in flocks and environment at Dongting Lake Region,and the infection rates of Class I is higher than vaccine and virulent strain,there is some virus pollution diffusion to some extent. Class I genotype 3 is the major epidemic strain,it is more closer genetic relationship to wild-bird. Therefore, it must pay attention to enhance the pathogen surveillance and molecular epidemiological research of Newcastle disease.
Keywords/Search Tags:circum-Dongting Lake Region, Newcastle disease virus, the F gene, the NH gene, Phylogenetic analysis
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