Abstract: Erythroblastosis was diagnosed in two flocks of Chinese local breed and one flock of layer chicken during 2010 and 2011. The age of birds was 110day, 90day and 20day, respectively. The main symptoms were characterized by emaciation, depressed and lethargy. At necropsy, numerous similar nodular lesions and resembling tumors were observed in one or more tissues. Some organs showed enlargement. A large number of erythrocytoblasts were observed in blood and bone marrow smears. Erythrocytoblasts were larger, basophilic cytoplasm and round nucleus. Histological examination showed that erythrocytoblasts were crowded in both blood vessels and mesenchym. Mitosis of erythrocytoblasts was often seen. No evidences showed Marek’s disease and reticuloendotheliosis, poisoning and metabolic diseases in these sick chickens. The PCRbased diagnosis showed that ALVJ specific fragment of 924 bp was obtained, rather than ALVA and ALVB. Immunohistochemistry results showed that a diffuse presence of ALVJ antigen in various tissues. Taken all data together, it demonstrated that erythroblastosis in the three flocks was induced by ALVJ. Erythroblastosis induced by ALVJ was found first time in China flocks. The etiology and mechanism of tumor spectrum expanded of ALVJ need to be further studied.

Key words: avian leukosis virus subgroup J, erythroblastosis, PCR, mmunohistochemistry