2019 Volume 72 Issue 10 Pages 608-613
Although enzootic bovine leukosis (EBL) usually occurs in cattle over 4 years of age, a diagnosis of EBL was able to be established in a 5-month-old crossbred steer. This animal showed marked swelling of the superficial lymph nodes at 134 days old. At 168 days old, swelling of the superficial lymph nodes deteriorated. A blood examination revealed the rapid elevation of the white blood cell count (104,000/μl ) with 89% atypical lymphocytes. In the necropsy, the abdominal lymph nodes were greatly enlarged. Histologically, tumor cells characterized by pleomorphism and atypia showed proliferation or infiltration in lymph nodes and a variety of internal organs. Real-time PCR showed an extremely high number of copies of proviral bovine leukemia virus (BLV) in the peripheral blood and the lymph nodes examined. B cell clonality tests showed biclonality growth of tumor cells. A diagnosis of EBL was made based on these findings. Analysis of bovine leukocyte antigen (BoLA) genes, associated with the susceptibility to BLV, showed BoLA-DRB3＊1101 and ＊1601 ; therefore, multiple factors are thought to have been implicated in the neoplastic transformation in the present case.
