Abstract
Enzootic bovine leukosis is one of the widespread chronic infectious diseases affecting cattle production. The causative agent is bovine leukemia virus (BLV), which primarily infects B lymphocytes and persists in the animal host for prolonged periods. The long latent period of infection and the absence of pronounced clinical signs in most cases make early detection of the disease difficult. Therefore, the use of reliable and accessible diagnostic methods for the detection of BLV infection is an important component of veterinary and sanitary control measures. This article presents a comparative review of the diagnostic capabilities of the agar gel immunodiffusion (AGID) test and enzyme-linked immunosorbent assay (ELISA) used for the serological diagnosis of enzootic bovine leukosis. The principles of the methods, their diagnostic significance, advantages and limitations, as well as their practical effectiveness for large-scale herd screening are considered. The AGID test is characterized by its simplicity, minimal requirements for specialized laboratory equipment, and long-standing use in veterinary practice. ELISA is characterized by high throughput, the possibility of standardizing test results, and suitability for processing large numbers of samples within a short period of time. The results obtained using the AGID and ELISA methods were compared using data from serological monitoring conducted in the West Kazakhstan Region in 2024–2026. A total of 11,642 cattle were examined. The AGID test identified 646 animals (5.5%) as positive, whereas ELISA identified 972 animals (8.3%) as positive. The higher detection rate obtained by ELISA indicates its greater diagnostic efficiency for screening studies. At the same time, the combined use of both methods within the veterinary monitoring system enables a more objective assessment of the prevalence of BLV infection and facilitates effective planning of disease-control and herd-health measures.