Epidemiological Investigation And Isolation And Identification Of Avian Leukosis Virus In Longsheng Feng-Chicken

Avian leukosis (AL) is a variety of tumor diseases and cases caused by a group of viruses related to avian leukosis virus (ALV), it causes low mortality and primarily affects the breeding flock and results in lower productivity and immunosuppression, and increases the condemnation. In our earlier epidemiological investigations five main local breeds of chickens in Guangxi had been found to be infected by ALV, but some small-number breeds of birds such as Longsheng Feng-Chicken has not yet been tested.Firstly, an epidemiological survey of ALV infection was performed in Longhand Feng-Chicken by using the commercial ELISA test kits. Totally217cloacal-swab samples and59egg-white samples and276sera samples were collected from276birds of a grandparent flock, and tested for ALV group-specific antigen p27, antibodies of ALV-A/B and J subgroups, respectively. Test results showed that the total p21positives of all the samples was26.45%(73/276), with higher positives of cloacal-swab samples (28.57%,62/217) than that of egg-white samples (18.64%,11/59), and much higher positives of A/B subgroup antibody (24.64%,68/276) than that of J subgroup (3.62%,10/276).Secondly, virus isolation and identification were performed by using the plasma samples collected from the p27-positive birds, based on the results of epidemiological investigation. Plasma samples were placed onto DF-1monolayer cells and passed blindly by two generations, and then the supernants of cell cultures were tested for ALV-p27antigen. The positive sample was tested for exogenous virus by PCR with ALV-specific primers and the positive then was used to amplify its membrane protein gene env and sequenced. Analysis of sequence identity with reference strains and a phylogenetic tree based on the sequences were done. Results shown that an ALV strain GX-F3was recovered and classified to be ALV subgroup B, by the results of its highest amino acid sequence identities of gp85gene with those of two reference strains of ALV-B subgroup by92.2%and92.8%respectively, and at the same group in the drawn phylogenetic tree.The results of the study demonstrated that Longsheng Feng-Chicken has been co-infected by exogenous ALVs of A/B and J subgroups, and subgroup A or B was the most prevalent subgroups in the flock. And a strain (GX-F3) belonged to ALV-B subgroup was successfully isolated and identified. The work will provide a useful foundation for the next eradication of avian leukosis in Longsheng Feng-Chicken.