Molecular characterization of bovine leukemia virus detected in dairy cattle herds from the Emirate of Abu Dhabi, United Arab Emirates.

Enzootic bovine leukosis (EBL) is an economically important disease of cattle caused by the bovine leukemia virus (BLV). Although BLV-seropositive dairy cattle were previously reported in the Emirate of Dhabi, UAE (EAD), molecular characterization of circulating BLV strains has not been undertaken. Therefore, the objectives of this study were to reassess the seroprevalence along with evaluating the genetic diversity of BLV strains circulating in dairy cattle in the EAD. Sera from 782 dairy cattle distributed across 11 farms were ELISA-screened and RT-qPCR testing of seropositive samples was followed by Sanger sequencing of the partial BLV env-gp51 gene (~ 423 bp) and phylogenetic analysis. The overall BLV herd seroprevalence was 27.3% (CI: 6.03%-61.00%), mean animal seroprevalence 33.5% (CI:30.20%-36.93%), and individual farm seroprevalence 28.00% (CI:19.00%-36.00%), 70.00% (CI:56.00%-84.00%), and 64.00% (59.00%-70.00%) for Farms 7, 11, and 14 respectively. Viral RNA was detected in 107 of 205 (52.2%) seropositive cattle, and phylogenetic analysis revealed a high genetic relatedness (~ 99.3-100.0%) among the BLV strains from the EAD. Additionally, study BLV isolates cluster under BLV-genotype 4 along with strains from Belgium, Russia and Vietnam. BLV infection is confirmed in EAD cattle, with circulating genotype 4 strains closely related to those from Europe and Asia, suggesting potential transboundary connections and underscoring the need for coordinated regional control measures. Future studies should focus on characterizing BLV infection risk factors in dairy cattle farms in the EAD. In the meantime, UAE livestock health authorities should urgently consider developing a national EBL control policy.