Bovine leukemia virus infection and control measures in the field
2016
Mekata, H. (University of Miyazaki, Miyazaki (Japan). Organization for Promotion of Tenure Track)
Bovine leukemia virus (BLV) is the etiological agent of enzootic bovine leukosis (EBL), which is characterized by fatal lymphosarcoma. According to a recent survey, approximately 30% of dairy and beef cattle in Japan are infected with BLV. Although many BLV-infected cattle remain asymptomatic carriers of the virus, approximately 30% suffer from persistent lymphocytosis (PL), and 5% develop EBL several years after infection. Food products from EBL cattle are prohibited by the Japanese government, and PL cattle tend to have a suppressed immune response. Therefore, BLV infection results in a huge economic loss to the farmer. Countermeasures against BLV infection on a farm include preventing new infections as well as reducing and increasing the number of BLV-infected and uninfected cattle, respectively. The various routes, such as blood-sucking insects, uninterrupted use of a needle and sleeve, dehorning and maternal milk transmit the virus. BLV can also be transmitted to a calf through the placenta or birth canal of an infected dam. High proviral load cattle are the primary source of horizontal and vertical infection. Therefore, culling, segregating and separating infected cattle, especially high proviral load cattle, are effective measures for preventing the transmission of BLV. This study introduces the BLV infection and the control measures for preventing BLV transmission in the field.
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