EN
The studies were carried out on 15 cows being at the 9th month of pregnancy and on their offspring. The newborn calves were fed on mothers’ milk. The cows were selected on the basis of positive immunodiffusion tests (ID). The studies comprised haematological, serological and virological tests, i.e. the isolation of bovine leukaemia virus on spleen foetus cells of cattle. In the light of the studies the syncytial test cannot be regarded as the only method in the diagnosis of early infections in cattle. The positive result of the test is dependent to much extent on the number of lymphocytes in the peripheral blood of animals.