Leucosis bovina / Bovine leucosis

ABSTRACT

The enzootic form of bovine lymphosarcoma is the most common malignancy of cattle, especially dairy cattle. Its etiological agent, the bovine leukemia virus (BLV) is evolutionarily related to human T-cell leukemia viruses types I and II (HTLV and HTLV II). These three retroviruses share common structural and biological features that distingush them from other members of the retroviral family. BLV is widespread in the cattle population of most countries. However, clinical disease occurs much less frecuently and direct economic losses from morbidity and mortality are significant for individual cattle owners but not excessively burdensome to the cattle and meat packing industries. The primary economic loss to the cattle industry from bovine leukosis is tha actual and potential loss of export markets for cattle and semen. BLV can infect human and simian cells "in vitro", there is serological evidence that BLV infect chimpanzes and in the literature can be found circunstantial evidence for an association of bovine and human leukemia. There is hight incidence of BLV infectión in dairy cattle and the virus is excreted in milk. At present, no evidence had been found that BLV or infected cattle are human health hazards, however, any conclusion would be premature. To clarify this issue investigations applying the most sensitive methods will be necessary. Several sensitive and specific methods for the detection og BLV and BLV infected cattle have been developed. These include infectivity assays, serological tests, and molecular hydridization techniques. Since under natural conditions BLV is predominantly transmitted by contact and prenatural conditions BLV is predominantly transmitted by contact and prenatal infection occurs in less than 20% of calves born to infected dams, control and/or erradication programs wuld be feasibly (AU)