Bovine Lymphoma (Leukosis, BLV) Study Guide

Overview and Clinical Importance

Bovine leukemia virus (BLV) is an oncogenic deltaretrovirus closely related to human T-lymphotropic virus types 1 and 2. BLV is the causative agent of enzootic bovine leukosis (EBL), the most common neoplastic disease in cattle worldwide. The virus integrates into B-lymphocyte DNA, creating a lifelong infection.

BLV infection follows a predictable progression: approximately 70% of infected cattle remain asymptomatic, about 30% develop persistent lymphocytosis (PL), and fewer than 5% develop lymphosarcoma (also called lymphoma), typically in cattle aged 4-8 years. The economic impact is substantial, with losses from reduced milk production, premature culling, carcass condemnation, and trade restrictions.

Etiology and Classification

Bovine Leukemia Virus Characteristics

BLV is an exogenous C-type oncogenic retrovirus belonging to the genus Deltaretrovirus, family Retroviridae. Key viral characteristics include: stable genome with approximately 97% nucleotide sequence homology among strains worldwide; integration into host B-lymphocyte DNA as a provirus; primary target cells are CD5+ IgM+ B-lymphocytes; the virus does not cause chronic viremia; and infection results in persistent antibody production.