HEMANGIOMA AND MYELOCYTOMAS INDUCED BY AVIAN LEUKOSIS VIRUS SUBGROUP J IN COMMERCIAL LAYER FLOCKS

An outbreak of hemangiomas and myelocytomas in 26 to 29-week-old egg-type chickens was observed in eastern China during late 2007. Mortality of the five flocks is 5 similar to 10%. Hemangiomas of various sizes were seen scattered over the trunk, claws, wings, and head. At necropsy, hemangiomas appeared in the pancreases, ovarian follicles and livers. In addition, numerous similar nodular lesions and resembling tumors were seen in the same tissues. Eighty-six serum samples from the five flocks were tested for the presence of ALV-J, ALV-A/B and REV antibodies by enzyme-linked immunosorbent assay (ELISA) technique. The overall seroprevalence of ALV-J antibodies was 61.63% (53/86), while ALV-A/B and REV antibodies were negative. Histologically, hemangiomas were typically cavernous hemangiomas with sponge-like architectures and myeloblastic infiltration, in which large multifocal islands of myeloblasts or myelocytes were observed. Immunohistochemistry with ALV-J and REV monoclonal antibodies revealed a diffuse presence of ALV-J antigen in hemangiomas, myelocytomas, bone marrow, liver, and other internal organs, especially in endothelial cells of small vessels, while there was no REV antigen. PCR analyses revealed the presence of ALV-J proviral sequences were more closely related to HPRS-103 than the to other Chinese field strains and ADOL-7501. No evidence of Marek's disease or lymphoid leukosis was found. The studies found that hemangiomas and myelocytomas appeared in same tissue at same time in layer chickens were induced by avian leukosis virus subgroup J (ALV-J).