Abstract
Enzootic bovine leukosis (EBL), caused by bovine leukemia virus (BLV), remains one of the key challenges in both dairy and beef cattle industries. Subclinical forms of infection, in which animals remain asymptomatic carriers for prolonged periods, pose a particular epidemiological threat. In this study, quantitative assessment of BLV proviral load was carried out using real-time polymerase chain reaction (qPCR) in 46 Simmental cattle. The β-actin/env ratio was used as a relative measure of viral load. The results were compared with hematological parameters classified according to the EC and JB keys. In animals with lymphocytosis identified by the JB Key (n = 8), the median β-actin/env ratio was 9.07, which was significantly lower than in animals with normal hematological profiles (median = 91; p = 0.0051), indicating high proviral load. In addition, a statistically significant inverse correlation was found between the results of the serological agar gel immunodiffusion (AGID) test and the β-actin/env ratio (ρ = –0.66; p < 0.001). These findings highlight the diagnostic value of an integrated approach combining qPCR, hematological classification, and serology for effective detection and controlof BLV infection, including in asymptomatic carrier animals