Public Health & BLV
The sustainability of the dairy industry is extremely vulnerable to consumer perceptions of food safety. The possible public health hazards of BLV have been extensively studied and debated. All available epidemiological evidence has supported the conclusion that BLV is not a human health hazard, but the issue may now be less clear. In BLV-infected cattle without lymphoma, it was previously believed that the virus induced only a benign proliferation of polyclonal B lymphocytes, but findings of more recent immunologic studies1,2,49,50 suggest that some lymphocyte proliferation may indeed be malignant in those cattle. Also, evidence suggests that BLV will grow in tissue cultures of human cells49,51, and it is now known that most humans exposed to the virus will produce antibodies49,52.Genes of BLV origin have been identified in human mammary cells, although there are conflicting reports regarding whether BLV DNA is found more frequently in cancerous or noncancerous tissues49,51,53. A helpful summary of the evidence has recently been published54.
In North America, where BLV is common in the cattle population, the rate of breast cancer in women remains lower than that in countries of Western Europe where BLV has been eradicated55. Rates of human leukemia also need to be compared between Europe and the U.S. Clearly the human health implications of BLV and other animal retroviruses need to be re-evaluated with the newer genetic tools that are now available to researchers.