Bovine leukemia virus (BLV) is the cause of enzootic bovine leukosis and has worldwide distribution. This is study reports presence and genetic diversity of BLV in cattle of two districts of Punjab, Pakistan. Blood samples (n=400) taken from local (n=200) and exotic (n=200) breeds of cattle were processed for complete blood count. Based on lymphocyte counts, samples were divided into two groups (A, lymphocytosis, B, normal lymphocytes) and tested through ELISA and nested PCR for serological investigations and molecular characterization respectively. In this study, animals of group A (32.5%) showed significantly greater seropositivity (P<0.05) against BLV than group B (16%). Furthermore, exotic breeds of cattle showed significantly greater seropositivity (18.75%) compared to the local breeds of cattle (5.5%). Nested PCR on each of the 10% seropositive and negative samples confirmed BLV infection in three seropositive exotic animals (30%). Phylogenetic analysis revealed the circulation of BLV genotype 1 in exotic breeds of cattle. Evaluation of various risk factors analysis demonstrated the strong positive association of BLV with age, herd size, parity, breeding (AI, Bull) and country of import. The animals found positive were imported from US, therefore there is a need to conduct a national epidemiological study on BLV to find out its true picture.
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