Abstract:

In June of 2011，sick chickens from a commercial flock at Zibo in shandong Province were sent to our lab for inspection.The flock size is 80 000.Main species breed in the farm were Black-bone silk fowl (BSF)，Ma-chicken and Hy-Line chicken.The BSF and Ma-chicken were reared in the same house， 4 000 each.The chickens were 360-day-old， and showed emaciation， listlessness，lethargy，pale comb.The mortality rate was about 10%.Hy-Line chickens in another house were not infected.Six of sick chickens were tested by gross，histopathology，blood smears observation and RT-PCR.The sequences of isolated viruses were analyzed by software.Necropsy observation showed enlargement of the liver and kidney，fibrosarcoma in chest，intestinal atrophy and liquefaction，soybean size of tumor nodules in pancreas.Histopathology observation showed that myelocytoma presented in the liver and arterial，and aneurysm existed in the leg.Fibrosarcoma appeared on the pectorales in BSF.Erythroblastoma of liver，spongy hemangioma of lungs were showed in Ma-chickens.Blood smear observation showed the occurrence of myeloid cell-like tumor cells，the number of neutrophils was significantly increased.Pathogen detection showed that ALV p27 antigen and antibody were both positive.The two kinds of chickens were both ALV-J positive in detection of RT-PCR.One and two strains of ALV-J were isolated from BSF and Ma-chicken，respectively.Comparing with the reference strains，the homologies of gp85 protein amino acid sequence were ranged from 82.3%-91.1%，suggesting greater genetic variability.It indicated that different host cross infection might happen and promote the rapid evolution of virus when mixed chickens infected with ALV-J.