Epidemiology Investigation And Isolates' Env Gene Analysis Of Avian Leukosis Virus In Qinzhou Area

Avian leukosis (AL) is caused by a group of Avian leukosis virus(ALV) associated with a variety of neoplasms. ALV caused huge economic loss in poultry industry and has been given great attention all over the world, now epidemiological investigation and eradication programs have been carrying on China.Since the research and eradication programs of AL were carried out in Guangxi province, the work in the major poultry production areas like Yulin, Guilin, Nanning and Baise has been done. The research now is chosen the coastal region in Guangxi-Qinzhou, to carry out the epidemiological investigation, virus isolation, genes sequencing and analyzing, with the aim to provide a complete epidemiological data of the major local chicken breeds and the surrounding waterfowls and other birds in Guangxi. And further for the prevailing subgroup/subgroups of ALV in the area and the genetic variations of the isolates by means of virus isolation, gene sequencing and analysis, providing the essentials for the eradication, the prevention and control of disease.Firstly, samples of totally 953 cloaca swabs, egg-white and sera were collected from the five main poultry breeds in Qinzhou, including Tiejiaoma chicken, "Sea duck" Sheldrake, Lion-head Geese, pigeon and turkey, were detected by using the commercial ELISA kits of ALV p27 antigen, A/B and J antibody (IDEXX Co., USA). Results showed that the only positive reactions were got from 13.04%(12/92) and 3.26%(3/92) of p27 antigen in cloaca swabs, egg-white respectively, and 5.08%(3/59) of A/B antibody in sera from Tiejiaoma chicken, while other samples were all negative in the reactions.Secondly, a totally 65 serum samples recovered from the 16 corresponding birds those were antigen-positive and antibody-positive,16 Tiejiaoma chickens of antigen-negative and antibody-negative and 33 turkeys of antigen-negative and antibody-negative were inoculated on to the DF-1 cells for the virus isolation of ALV. The cell supernatant and the cells of F2 generation cell cultures were detected respectively by PCR and ELISA, and the positive samples were further identified by the amplification, sequencing and analysis of the viral env gene. The result showed that two isolates of subgroup J ALV were recovered and named as QZ2 and QZ14 respectively. The sequence comparison of genes found that the nucleotide homology of env was 95.7% between QZ2 and QZ14; the homology of nucleotide and encoding amino acid of gp37 were more than 90% between the isolates and subgroup J reference strains, the nucleotide homology of env and gp85 were also more than 90% between the isolates and subgroup J reference strains except ADOL-7501, the amino acid homology of gp85 were 70.5%?90.9% between the isolates and subgroup J reference strains, with the highest with HPRS103 strain at 90.9%; the nucleotide homology of U3 were 87.6%-92.9% between the isolates and subgroup J reference strains, and the E element of QZ2 was near intact, while that of QZ14 was found a deletion of five nucleotides.The results of the study demonstrated that only Tiejiaoma chickens has been infected with ALV among the five main breeds of poultry in Qinzhou, and these ALVs were subgroup J. And the gene sequence analysis found that the genetic variations were happened in different genes of QZ2 and QZ14 isolates.