Eradication of bovine leukemia virus infection from a high-prevalence herd, using radioimmunoassay for identification of infected animals
Ferrer, J.F.
Journal of the American Veterinary Medical Association 180(8): 890-893
1982
ISSN/ISBN: 0003-1488 PMID: 6282793 Document Number: 184265
Radioimmunoassay (RIA), using the virion glycoprotein antigen, was applied in an attempt to eradicate bovine leukaemia virus (BLV) infection from a herd in which virtually all the adult cattle were infected. Considering that most calves born to BLV-infected cows are negative for BLV at birth and remain negative for the first several months of life, the eradication programme was based on the identification and isolation of the BLV-free calves born to infected cows. Twenty-five calves reared on colostrum and milk from their infected dams were classified as BLV-free on the basis of negative results in the RIA at 6 to 8 and 8 t 11 months of age. These animals were maintained in either complete (10 calves) or partial (15 calves) isolation from infected cattle and were examined at regular intervals for BLV and BLV antibodies. With the exception of one calf in the group raised in partial isolation, the animals remained free of BLV up to the time of the last evaluation, when they were 32-35 months old. At these ages, more than 90% of the non-isolated cattle in the herd were BLV-positive. This eradication trial would have failed if, in the first procedure used to classify the calves as BLV-free, the agar gel immunodiffusion test instead of the RIA had been used. Inasmuch as the 25 calves in this study were fed colostrum and milk from their dams, the fact that only 1 of the calves became infected during the 26 to 29 months of observation provides further evidence that milk-borne transmission of BLV is infrequent and perhaps inconsequential.