Retrospective analysis showed that the reason for the wide spread of the leucosis of cattle in the world in the 5th and 6th decade of the XX was the “world industrial- technological revolution in the livestock raising” - transition from the individual raising and the manual milking of cows to the formation of large-scale milk farms and complexes with the mechanical milking of cows with common equipment, without taking into account their status on the leucosis, since. at that time there were no known methods of detecting VLB  infected animals. It has been proven that today the process of treatment of cattle from leucosis is absolutely controlled one and it depends on the level of the professional (veterinary) ethics of the maintenance of animals. It has been established that in the period since 1991 until 2013, the infection of animals with VLB in Moldova has decreased almost tenfold, from 48.8% to 4.96%, while 4 regions - were free from the leucosis, 10 regions - at the stage of completion of the liquidation of this illness.