Bovine leukemia virus detection and dynamics following experimental inoculation

Bovine leukemia virus (BLV) infects more than 40% of the United States cattle population and impacts animal health and production. Control programs aiming to reduce disease prevalence and incidence depend on the ability to detect the BLV provirus, anti-BLV antibodies, and differences in blood lymphocyte counts following infection. These disease parameters also can be indicative of long-term disease progression. The objectives of this study were to determine the timing and to describe early fluctuations of BLV-detection by qPCR, ELISA, and lymphocyte counts. Fifteen Holstein steers were experimentally inoculated with 100 μL of a blood saline inoculum. Three steers served as in-pen negative controls and were housed with the experimentally infected steers to observe the potential for contract transmission. Five additional negative controls were housed separately. Steers were followed for 147 days post-inoculation (DPI). Infections were detected in experimentally infected steers by qPCR and ELISA an average of 24- and 36 DPI, respectively. Significant differences in lymphocyte counts between experimentally infected and control steers were observed from 30 to 45 DPI. Furthermore, a wide variation in peak proviral load and establishment was observed between experimentally infected steers. The results of this study can be used to inform control programs focused on the detection and removal of infectious cattle.