Bovine Leukemia Virus: Global Prevalence and Localized Resurgence in China Revealed by an Integrated Meta-Analysis and Case Series.

[BACKGROUND] Bovine leukemia virus (BLV), the causative agent of enzootic bovine leukosis (EBL), causes substantial economic losses in the global cattle industry. While some regions have made progress in terms of control, the global epidemiological landscape and situation in China have not been fully elucidated. This study aimed to clarify the current global prevalence of BLV based on existing reported studies and investigate its alarming resurgence in China.

[METHODS] We conducted an integrated study comprising a systematic review and meta-analysis of the global literature from 2010 to 2025 and a detailed case series investigation from Hubei Province, China. The meta-analysis followed PRISMA guidelines to calculate the pooled prevalence and identify risk factors. The case series included pathological examination, histopathology, and molecular detection (real-time PCR and nested PCR) to confirm BLV infection and genotype in clinical cases.

[RESULTS] The meta-analysis, which included 44 studies, revealed a global pooled BLV prevalence of 23.24%, with a significant decline observed in studies published after 2018 (4.35%) compared with those published before 2018 (20.31%). Subgroup analyses indicated marked differences in detection rates across sample types and detection methods. Besides, significantly greater prevalence was also observed in cattle more than 12 months. In stark contrast to this global trend, the pooled prevalence in China was 16.80%, which masked a severe high-burden endemicity in Hubei Province, where a 49.41% positivity rate (126/255) was detected across three farms. Pathological and molecular analyses of four clinical cases from these farms confirmed BLV-induced lymphosarcoma and identified the circulating virus as genotype G6.

[CONCLUSION] This study delineates an apparent decline in reported BLV prevalence globally, contrasted with a severe localized resurgence in Hubei Province, China: an apparent decline in reported prevalence based on the available data in BLV prevalence, alongside a severe and ongoing resurgence in a major Chinese cattle-farming region. These findings underscore that national and global averages can obscure dangerous local epidemics. The situation in Hubei serves as a crucial warning, demanding immediate, targeted interventions, including enhanced surveillance, stringent biosecurity, and farmer education, to curb the spread of BLV.