Аннотация
The article presents up-to-date information on the etiology, epizootiology, and pathogenesis of bovine leukemia virus (BLV). The structure and functions of the main viral genes are considered, with emphasis on their role in replication, integration into the host genome, and the formation of persistent infection. Particular attention is paid to the regulatory proteins Tax and Rex, which play a crucial role in viral persistence and tumor development. The main routes of virus transmission are described, including horizontal, vertical, and iatrogenic pathways, as well as clinical manifestations such as asymptomatic infection, persistent lymphocytosis, and tumor form (lymphosarcoma). Data on the spread of BLV in Kazakhstan from its first registration to the present are summarized, and the dynamics of the epizootic situation across different regions of the country are analyzed. It is emphasized that the virus continues to circulate in several areas, which necessitates enhanced monitoring, the application of molecular diagnostic methods, and the development of comprehensive preventive measures. In addition, the scientific analysis of the article examines the economic consequences of bovine leukemia virus for farms, including decreased milk productivity, herd reduction, limited export potential, and expenses for veterinary and sanitary measures.