Evaluation of total white blood cell count as a marker for proviral load of bovine leukemia virus in dairy cattle from herds with a high seroprevalence of antibodies against bovine leukemia virus.

Objective: To determine the reference interval for WBC counts in Holstein dairy cows from herds with high seroprevalence for anti-bovine leukemia virus (BLV) antibodies, analyze the correlation of total WBC counts and blood proviral load (bPVL) in BLV-infected animals, and determine whether total WBC count can be used a hematologic marker for in vivo infection.

Animals: 307 lactating cows from 16 dairy herds with high BLV seroprevalence.

Procedures: Blood samples were collected for assessment of plasma anti-BLV p24 antibody concentration (all cows), manual determination of WBC count (161 BLV-seronegative cows from 15 herds), and evaluation of bPVL (146 cows from another herd).