Bovine leukosis: An example of poor disease monitoring of international livestock shipments to developing countries

Over the past few years, cattle imported into a number of countries have been shown to carry antibodies against bovine leukosis virus (BLV), the cause of enzootic bovine leukosis. The disease, imported into England via shipments of Canadian dairy cattle in the late 1970s, is still a significant problem in the United Kingdom. Many countries now require a blood test for serum antibodies to BLV as a precondition of shipment from certain endemic countries. Those cattle positive for BLV are excluded from shipment. Well-documented cases of shipments of hundreds of Canadian cattle without testing for BLV has been obtained. These shipments were to the African country of Malawi where the BLV status is unknown. Also, although the United States is endemic for BLV, most of the recent live cattle exports were received by countries which did not require a blood test for BLV. Of the 44 countries that imported U.S. cattle during 1982 and 1983, only 13 required BLV antibody testing before shipment. This report concerns one disease in one species. The millions of livestock shipped yearly between the countries of the world may harbor many viruses at risk of being introduced into susceptible animal populations. While international animal health agencies are doing a credible job of providing disease surveillance to member countries, there still needs to be improvements in disease information dissemination.