Studies on bovine leukosis as it is seen in England and Wales

A random series of 14 clinical cases of bovine leukosis as it is seen in England and Wales has been studied clinically, haematologically, serologically (by the indirect fluorescent antibody test and later by agar gel immunodiffusion as well), virologically (for evidence of bovine leukaemia virus--BLV) and using the electron microsocope to count intranuclear pockets in circulating lymphocytes. Additionally calves have been inoculated with whole blood and a tissue lymphocyte suspension from the first six cases and the experimental calves studied periodically by the same methods. Herds of origin of the field cases were examined for clinical evidence of lymphomatosis, for evidence of leukaemia and for serum antibody to BLV. To date no evidence has been found to indicate that the field cases were other than sporadic and non-contagious. Neither BLV nor specific antibody has been demonstrated; no increase in lymphocytic nuclear pockets has been seen; the transmission tests are still apparently negative. It would appear that sporadic bovine leukosis and enzootic bovine leukosis are aetiologically separate entities.