Enzootic Bovine Leukosis
Author(s): Juan García-Diez, Dina Sofia Faria Pinto Moura, Isabel Cristina Ribeiro Pires, Cristina Maria Teixeira Saraiva
Abstract: Bovine leukosis is a cattle disease caused by the retrovirus, bovine leukaemia virus (BLV). Although the natural host of BLV is domestic cattle, it is also considered a model for understanding pathogenesis and development of novel therapies for Human T-cell lymphotropic virus. Cattle infected do not usually present clinical signs, however a persistent lymphocytosis and development of tumour lesions may occur. Tumour lesions have been described in the abomasum, central nervous system, eye, heart, lymph nodes, liver, spleen, spine, uterus and other structures. EBL is responsible for high economic losses derived mainly from trade restrictions and decreased milk yield. Many countries have implemented specific control and surveillance programs for their eradication. These programs are based test-and-slaughter and consist in blood sampling of cattle periodically and compulsory slaughter of those positives. According to the legal criteria in Europe, official country or regional freedom from EBL require that at least 99.8% of herds are free from BLV infection. Besides some findings indicated the presence of infected viral particles in foodstuffs, further studies are necessary to confirm the chance of BLV transmission to humans through foodstuff consumption.