An evaluation of the role of milk in the natural transmission of BLV.

In order to evaluate the role of milk in the transmission of BLV, the presence of the virus and viral antibodies was investigated in cattle that were born to, and nursed on, infected dams and then raised in isolation or in contact with infected animals. Only 3 of the 17 isolated cattle became infected during 25-29 months of observation. During the same period of time, all 17 cattle raised in contact with BLV-positive animals developed BLV infection. From these results, it is apparent that milk-borne transmission of BLV, if it occurs, is much less frequent than contact transmission.