[Role of vertical transmission and seminal fluid in the infectious leukemia process]

Studied was the occasional role played by vertical transmission of the leukotic infection via the placenta under experimental conditions and in the field. Studies were also carried out to establish the transmission of the infection through the semen as well, using bull semen and test lambs as most susceptible to the virus of bovine leukosis. It was found that at the experimental infection of sheep with the bovine leukosis virus intraplacental infection of part of the fetuses took place. On dairy farms with a widely spread infection (more than 50 per cent) in cattle the newborn calves were found to respond positively immediately after birth and prior to sucking colostrum, having specific leukosis antibodies, though in a low percent. No transmission of leukosis was found with the semen of leujotic bulls.