| Avian leukemia(AL)refers to a kind of infectious tumor disease caused by the mass proliferation of some types of cells in the hematopoietic tissue of poultry caused by avian leukosis virus(ALV),which belongs to the family of avian retrovirus.It has caused huge economic losses to the poultry industry.Currently,no effective vaccines and drugs are available,which can only be effectively controlled through the eradication of the breeders.However,in the testing of eradication,the results of different methods applied are inconsistent,and the results of different testing days of age are also different.The studies here intend to explore some key technologies and prevention measures for the AL eradication of local breeds of chickens,combined with my own work in the breeding company to do the "Two white" eradication research,and search the practical techniques suitable for eradication and control of the AL on the local chicken farms.In the initial stage of eradication local chicken breed 1 of DGGX18 Company,plasma samples of chickens were collected at 23 W and 27 W of age respectively,and then inoculated onto the DF-1 cell cultures before the ELISA detection for ALV-P27 antigen.Results showed that the positive rates of 23 W was 46.05%,much higher than 23.68% of 27 W;The local chicken breeds A,B and C from DXGX11 Company were selected,and the ELISA detection for ALV-P27 antigen in the egg-white samples from the first 3 different eggs of the same hen was used.The results showed that the detected positive numbers of A,B and C breeds for one egg sample were 64(5.65%,64/1132),88(3.53%,88/2496)and 122(12.56%,122/971),respectively and those for 2 egg samples were 71(6.27%,71/1132),91(3.65%,91/2496)and 179(18.43%,179/971),respectively,while those for 3 egg samples were 86(7.60%,86/1132),103(4.13%,103/2496)and 194(19.98%,194/971),respectively.The local chicken breeds A,B and D of DGGX11 Company were selected,and the ELISA detection for ALV-P27 antigen in the egg-white samples at 23 W(3 eggs)or 27W(1 egg)of age and the virus isolation by detecting the P27 antigen on the DF-1 cell cultures inoculated with the plasma samples from the same hen were both used.For breed A,the positive numbers of egg-white testing and virus isolation were 17(1.75%,17/974)and 13(1.33%,13/974),respectively,and 0bird was positive for both detections.For breed B,the positive numbers of egg-white testing and virus isolation were 37(1.74%,37/2124)and 72(3.39%,72/2124),respectively,and 10 birds were positive for both detections.For breed D,the positive numbers of egg-white testing and virus isolation were 26(5.87%,26/443)and 19(4.29%,19/443),respectively,and 3 birds were positive for both detections.In order to explore the relationship between the ALV infection and the pullorum disease,local chicken breeds 1,2 from DGGX18 Company and local breed D from DGGX11 Company were selected,and the ELISA detection for ALV-P27 antigen in the egg-white samples(for breed 1,2)or the virus isolation by detecting the P27 antigen on the DF-1 cell cultures inoculated with the plasma samples(for breed D)were used to detect the infection of ALV,while the serum plate-agglutination-test with pullorum disease-fowl typhoid multivalent plate-agglutination-test antigen was used to detect the infection of Salmonella pullorum-fowl typhoid.The results showed that the positive rates of ALV-infection were 26.00%,1.00% and 11.72% respectively in the birds of pullorum disease-fowl typhoid positive in the three different breeds 1,2 and D,while those were 17.84%,0.38% and 8.76% respectively in the birds of pullorum disease-fowl typhoid negative.The clinical tumor tissue samples and the sterile plasma samples of the local chicken breed D,which was at the early stage of the eradication program in the DGGX11 Company were used to isolate ALV by innoculating onto the DF-1 cell cultures and subsequently tested with ALV-P27 antigen ELISA kit and the PCR detections for ALV-J env gene.It was confirmed that 5 clinical-sample isolates and 5 plasma-sample isolates of ALV-J were obtained,and their env genes were then sequenced and analyzed.Sequences BLAST results showed that all the 10 isolates belonged to ALV-J.Based on the phylogenetic tree analysis of env gene and gp85 gene.10 isolates were grouped in the same branch and also in the same branch with other ALV-J reference strains.These isolates could also be further divided into two sub-branches,7 of them including 3 clinical-sample isolates and 4 plasma-sample isolates were gathered together,indicating that these clinical-sample isolates and the plasma-sample isolates have the same origin.We speculated that the incompleteed eradication of ALV is one of the main reasons for the clinical AL cases.In addition,3 of them including 2clinical-sample isolates and 1 plasma-sample isolates were gathered together with a previous live vaccine isolate GX14ZS14 in another sub-branch,indicating that the contaminated live vaccine carrying pathway might be a source of the ALV-J infection in the breeder flock and the clinical cases in the company.The results of the studies demonstrated that for the eradication practice,the positive rate of the virus isolation with the plasma sample at 23 W of age was much higher than that at 27 W of age.The positive number detection rate with the first three eggs was higher than those with one single egg and the first two eggs.The coincidenceship between the positive detections of virus isolation with plasma sample and the ALV-P27 with the egg-white sample was low.The positive rate of the ALV-infection in chickens of pullorum disease-fowl typhoid positive was higher than that in chickens of pullorum disease-fowl typhoid negative.Based on the analysis of the gene sequence of the isolates from the clinical-sample and the plasma-sample,the ALV-J contamination source and transmission pathway in the breeders of the company were verified. |
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