Predicting an increased risk of severe clinical mastitis and economic loss using a threshold value of bovine leukemia virus proviral load.

Objective: To establish a threshold value of bovine leukemia virus (BLV) proviral load (PVL) to identify increased risk of severe clinical mastitis, and to examine the prognosis and economic loss of clinical mastitis based on the newly established PVL cut-off value.

Animals: 97 lactating Holstein cows with clinical mastitis.

Methods: Blood and milk samples were collected aseptically from each cow.