Decades in the past, concern was raised that the milk of dairy cows continuously comprises a leukemia-causing virus—extra particularly, bovine leukemia virus (BLV), the main most cancers killer amongst dairy cattle. Most U.S. dairy herds are contaminated with the most cancers virus. “Thus the question of whether dairy cows naturally infected with BLV release infectious virus into milk is an important public health consideration” and the topic of my video Is Bovine Leukemia Virus in Milk Infectious?.
Researchers on the University of Pennsylvania determined to place it to the take a look at. And certainly, infectious virus was demonstrated in the milk of 17 of the 24 cows examined, indicating that “humans are often orally exposed to BLV.” Just as a result of we’re uncovered to it doesn’t imply it’s inflicting human illness, although. How do we all know BLV may even infect human cells? We didn’t till 1976 when it was found that BLV can certainly infect human, chimpanzee, and rhesus monkey cells. Nevertheless, that also doesn’t imply BLV essentially causes most cancers in different species.
Researchers can’t lock human infants in a cage and feed them contaminated milk, however they will cage toddler chimpanzees. Chimps Bois and Roger have been fed contaminated milk, developed leukemia, and died. Until then, we didn’t even know chimps might get leukemia. The indisputable fact that BLV-infected milk appeared to transmit or induce leukemia in our closest residing kinfolk definitely did increase the stakes, however human beings will not be chimpanzees. Yes, our DNA could also be 98 p.c equivalent, however we might share 60 p.c of our DNA with a banana. We want human research.
We can’t do interventional trials in this case, because of these pesky Nuremberg ideas, however what about observational research? Do cattle farmers have increased charges of most cancers? Apparently so. This discovering led some to counsel that “milk- and egg-borne viruses may be highly important in the pathogenesis [or development] of human leukemia and lymphoma,” however farmers could also be uncovered to all types of potential carcinogens, corresponding to pesticides. Large animal veterinarians can also have extra leukemia and lymphoma, however some are additionally “particularly lax in the use of X-ray protective equipment,” so it didn’t essentially have something to do with viruses.
We wanted so-called serology research, testing folks’s blood for antibodies towards the virus, which might show human publicity, and we bought them. Ten totally different research regarded for BLV antibodies in most cancers sufferers and non-cancer sufferers, creamery staff versus workplace staff, veterinarians, unpasteurized milk drinkers, and extra. “Not one of these studies found a single individual with antibodies to BLV…” As a end result, in 1981, the case was closed: “Therefore, there is strong serological evidence to indicate that BLV is not transmissible to man.” However, the strength of the proof is just as sturdy because the strength of the take a look at. Chimpanzees Bois and Roger didn’t develop detectable antibodies both, and so they died from BLV.
The checks out there a handful of many years in the past have been probably not delicate. “Clearly, the question of whether BLV poses a public health hazard deserves thorough investigation” utilizing extremely delicate molecular probes. It would take just a few many years for us to get such an examination, and I talk about these landmark findings in my movies The Role of Bovine Leukemia in Breast Cancer and Industry Response to Bovine Leukemia Virus in Breast Cancer.
Thankfully, feline leukemia virus doesn’t seem like transmissible. See Pets and Human Lymphoma.
Michael Greger, M.D.
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