Abstract: 15 Qingyuan MA chickens which appeared obviously clinical symptom and were tested to be avian leukosis positive were selected. The tumor organs, such as liver, spleen, kidney and so on, were carried on histopathology and PCR diagnosis. The pathology tissue slices from organs of liver, kidney, spleen, marrow, gland stomach, heart, lung, pancreatic gland ovary and so on, were observed, results showed that the proliferation of massive lymphoblasts or scatter and of small lymphomyelocytes were observed. The PCR identification indicated that all 15 samples can amplify a fragment about a length of 545 bp, which consisted with the expected size. The results suggested that all 15 isolates were the ALV-J avian Leukosis viruses.

Key words: Qingyuan MA chicken; avian leukosis; histopathology; PCR