The historical background of the control of enzootic bovine leukosis in Estonia.

The authors describe the history of enzootic bovine leukosis (EBL) in Estonia, including the occurrence and distribution of disease within the cattle population, and the factors which have influenced disease spread since the 1950s. The principles of various control schemes which were applied from 1960 to 1994 are also surveyed. Considerable progress in eradicating EBL has been achieved during recent years, as a result of systematic serological herd testing, and the slaughter of cattle infected with bovine leukaemia virus (BLV). The decrease in the numbers of EBL-affected cattle may be expressed by the reduction in the number of leukotic tumour cases recorded annually: from an average of 180 cases per 100,000 cows in the 1980s to four cases in 1994; and by the decrease in the average prevalence of BLV-infected animals in the cattle population, from 31.4% in 1989 to 0% in 1994. The national EBL control programme will be continued. It is hoped that Estonia can be declared EBL-free within the coming years.