| Avian leukosis is caused by avian leukosis virus(ALV),which is characterized by immunosuppression,growth retardation and a variety of neoplastic disease.In recent years,there have been many reports about ALV in yellow-feathered broilers and indigenous chicken breeds in China.At present,there are no effective commercial vaccines and drugs for the control of avian leukosis,it is considered that the most effective way to control avian leukosis is to carry out strict eradication of avian leukosis in breeder flocks.The role of cocks and semen in ALV transmission is not only an important theoretical issue in the process of avian leukosis eradication,it is also a practical technical problem related to eradication effect,it is an important significant for AL eradication to understand the infection and virulence of ALV in cocks and semen,and the correlation between the infection of ALV in semen and blood.In this study,plasma and semen were used for virus isolation,and the isolation,identification and investigation of ALV were carried out from twelvesyellow-feathered broilers cocks in Guangxi,the genome of one of the recombinant ALV was sequenced and analyzed,to provide necessary basic data for AL eradication program.In order to understand and develop the AL eradication of the infection of ALV in twelves yellow-feathered broilers cocks,in this study the blood and semen samples were collected from twelves yellow-feathered broilers cocks for virus isolation,the isolation,identification and epidemiological investigation of ALV were carried out.The results showed that the positive rates of blood virus isolation from twelves yellow feathered-broiler cocks were 0.74%(1/135)?3.46%(8/231)?1.37%(1/73)?3.78%(9/238)?8.12%(38/468)?5.33%(73/1370)?5.45%(9/165)?2.13%(1/47)?0(0/29)?2.5%(1/40)?1.72%(3/174)?2.5%(5/200),respectively,the positive rates of semen virus isolation were 0.74%(1/135)?1.73%(4/231)?1.37%(1/73)?1.26%(3/238)?1.71%(8/468)?6.64%(91/1370)?4.24%(7/165)?0(0/47)?0(0/29)?0(0/40)?5.17%(9/174)?1.50%(3/200),respectively,through analysis and comparative study of data found that the virus isolation from samples of semen and blood are not consistent in the same cock from multiple chicken flocks,the positive rate of partial semen virus isolation was higher than that of blood virus isolation,the sequencing analysis of gp85 gene of six isolates from four chicken farms showed that all the isolates belong to subgroup J(ALV-J).The results showed that ALV is still prevalent in several yellow feathered-broiler cocks in Guangxi,and further eradication programs areneeded to control ALV.It was found that the wild strain GXRJ01 was suspected to be an emerging natural recombinant ALV by sequencing.In order to understand the molecular characteristics of GXRJ01,the whole genome of GXRJ01 was obtained by sequencing and splicing after amplification with different gene regions by multiple pairs of overlapping primers.The homology of env gene and representative BR19 of ALV-J was 96.8%,the homology between long terminal repeat(LTR)and subgroup E(ALV-E)was 94.9%-98.4%.It is speculated that GXRJ01 is probably a wild strain produced by natural recombination of ALV-J gene and LTR of ALV-E.The above results further showed that there was complexity and diversity of ALV gene in yellow-feathered broiler in Guangxi,it is speculated that there may be mixed infection of multiple subgroup strains in the yellow-feathered broiler flocks,which increases the probability of producing recombinant strains,suggest that eradication program should be carried out as soon as possible to avoid the continuous prevalence and recombination of ALV in the yellow-feathered broiler flocks.In this study,two methods of virus isolation and identification in plasma and semen were used simultaneously,the investigation of ALV infection in twelves different yellow-feathered broilers cocks were completed.The results of virus isolation and identification in plasma and semen were found to be inconsistent in the yellow-feathered broilers cocks of ALV infection.In addition,the genome sequence of a natural recombinant ALV was found and analyzed,theresults provide new theoretical data support for promoting the eradication of avian leukosis in yellow-feathered broiler. |
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