Report of bovine leukemia virus (BLV) <i>in situ </i>detection in primary cultures of bovine mammary epithelial cells

A BLV infected cow, with high proviral load and persistent lymphocytosis, was used for this study. After euthanasia, nipple epithelial material was collected, disaggregated, and primary cultures were established. After 5 passages, viral proteins could be detected by immunocytochemistry, indicating that the virus is capable of expressing proteins in the cytoplasm of the host cell. Proviral load was quantified by qPCR in blood and milk of the infected animal. The presence of viral particles in milk and meat for human consumption has been described previously Therefore this report warns us of the possibility of BLV transmission to humans, with the potential risk of zoonotic disease.