Is Bovine Leukemia Virus in Milk Infectious?

Image Credit: Wikimedia Commons. This image has been modified.

Should You Be Concerned about Bovine Leukemia Virus in Milk?

Decades ago, concern was raised that the milk of dairy cows frequently contains a leukemia-causing virus—more specifically, bovine leukemia virus (BLV), the leading cancer killer among dairy cattle. Most U.S. dairy herds are infected with the cancer 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 subject of my video Is Bovine Leukemia Virus in Milk Infectious?.

Researchers at the University of Pennsylvania decided to put it to the test. And indeed, infectious virus was demonstrated in the milk of 17 of the 24 cows tested, indicating that “humans are often orally exposed to BLV.” Just because we’re exposed to it doesn’t mean it’s causing human disease, though. How do we know BLV can even infect human cells? We didn’t until 1976 when it was discovered that BLV can indeed infect human, chimpanzee, and rhesus monkey cells. Nevertheless, that still doesn’t mean BLV necessarily causes cancer in other species.

Researchers can’t lock human infants in a cage and feed them infected milk, but they can cage infant chimpanzees. Chimps Bois and Roger were fed infected milk, developed leukemia, and died. Until then, we didn’t even know chimps could get leukemia. The fact that BLV-infected milk appeared to transmit or induce leukemia in our closest living relatives certainly did raise the stakes, but human beings are not chimpanzees. Yes, our DNA may be 98 percent identical, but we may share 60 percent of our DNA with a banana. We need human studies.

We can’t do interventional trials in this case, thanks to those pesky Nuremberg principles, but what about observational studies? Do cattle farmers have higher rates of cancer? Apparently so. This finding led some to suggest that “milk- and egg-borne viruses may be highly important in the pathogenesis [or development] of human leukemia and lymphoma,” but farmers may be exposed to all sorts of potential carcinogens, such as pesticides. Large animal veterinarians may also have more leukemia and lymphoma, but some are also “particularly lax in the use of X-ray protective equipment,” so it didn’t necessarily have anything to do with viruses.

We needed so-called serology studies, testing people’s blood for antibodies against the virus, which would prove human exposure, and we got them. Ten different studies looked for BLV antibodies in cancer patients and non-cancer patients, creamery employees versus office employees, veterinarians, unpasteurized milk drinkers, and more. “Not one of these studies found a single individual with antibodies to BLV…” As a 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 evidence is only as strong as the strength of the test. Chimpanzees Bois and Roger didn’t develop detectable antibodies either, and they died from BLV.

The tests available a handful of decades ago were not really sensitive. “Clearly, the question of whether BLV poses a public health hazard deserves thorough investigation” using highly sensitive molecular probes. It would take a few decades for us to get such an examination, and I discuss those landmark findings in my videos The Role of Bovine Leukemia in Breast Cancer and Industry Response to Bovine Leukemia Virus in Breast Cancer.

Thankfully, feline leukemia virus does not appear to be transmissible. See Pets and Human Lymphoma.

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations:


Michael Greger M.D., FACLM

Michael Greger, M.D. FACLM, is a physician, New York Times bestselling author, and internationally recognized professional speaker on a number of important public health issues. Dr. Greger has lectured at the Conference on World Affairs, the National Institutes of Health, and the International Bird Flu Summit, testified before Congress, appeared on The Dr. Oz Show and The Colbert Report, and was invited as an expert witness in defense of Oprah Winfrey at the infamous "meat defamation" trial.

45 responses to “Should You Be Concerned about Bovine Leukemia Virus in Milk?

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  1. Do we know if it was tested, or what the effect of ‘ultra pasteurization’ has on the virus?
    Yeah, I can’t understand why this was posted on NF.o…. it would better have been submitted to Dairyman’s Monthly or somesuch.

    Presumably 99.99% of the people here have only had exposure to pasteurized dairy products.

    (I’m one of the exceptions… I was raised on raw milk from the family milk cow.

    1. Lonie,

      I am not a math person, but if you are right that 99.99% of the people here have only had exposure to pasteurized dairy products, but when they tested the humans for the antibodies, 74% tested positive, well something fishy, or should I say beefy or milky is going on there.

        1. it says that they can be ‘decativated’ though which is the same thing.

          I wonder how many companies fail tp properly pasteurise milk and milk products? It does happen but perhaps not all incidents result in recalls.

          1. Tom,

            I don’t really trust any food industry to be perfect.

            Almond milk tested positive for cow’s milk in the US. How does that even happen?

            And, now that it has been discovered, how likely is it that it happens all of the time?

        2. That belief has been discounted. A 15% increase in pressure kills viruses. See Made by Cow. Their raw milk is now for sale in Australia due to this process. It will revolutionize the global dairy herd and dairy consumption over the next ten years.

          The bigger question is why the public has not been informed about the very real threat of BLV.

  2. I had Bovine TB when I was 14, in 1959. I am a farmers daughter and we had milking cows, that then, were not tested for TB. Badgers carry the disease. In those days you didn’t see any badgers, or very rarely, the cows pick it up, and hey presto!! My mother had luekemia and died at the age of 65. My brother had Crohn’s disease and died at 55. Might not be any connection but who knows?

    1. Jenny,

      Dr. Greger’s video on the topic shows that women were exposed and that the virus was in the cancer tissue samples, so it could be.

      “The presence of bovine leukemia virus DNA in breast tissues was strongly associated with diagnosed and confirmed breast cancer. As many as 37% of breast cancer cases may be attributable to BLV exposure. As many as 37% of human breast cancer cases may be attributable to exposure to bovine leukemia virus.”

      1. That 37% number when converted into people means 99,160 women are impacted by the Bovine Leukemia Virus annually and that only means it has been detected in them, not that they have it and it hasn’t been detected yet. The impacted number could very well be 100% of female dairy consumers. We don’t know. What I do know is that the public needs to know what is going on. To withhold information of this significance is a crime. At least in Canada it is.

  3. I am grateful for the deep knowledge Dr. Greger shares on this site and elsewhere. However my conscience can’t let me be silent about the rather flippant way this article referred to caging infant chimpanzees. It’s abhorrent that they had to endure this treatment and then die. All lives matter. Non-human life and well-being is just as important and worthy of protection as that of humans. And, as a retired nursing researcher, I don’t view the Nuremberg principles as “pesky.” Please, show a little more respect for safeguarding the rights of all beings used subjects for medical research. We literally owe our lives to them.

    1. Animal testing is abhorrent. But please remember that Greger was a director of the Humane Society with a responsibility for farm animal welfare. try to think about what he said and the context

      Just to spell it out ……….. it’s sarcasm not flippancy. There’s a difference.

      1. Yes, Dr. Greger works seriously hard at achieving the cultural changes, which you are valuing.

        He is trying to keep a balance between the seriousness of the subjects and staying light-hearted enough to not lose the base of his audience.

        He is an interesting mix of lighthearted in his presentations, but very serious in his food and medicine political actions.

    2. Another person lacking any humor or sensitivity to the use of language. Americans are so tight-assed.

      ‘Non-human life and well-being is just as important and worthy of protection as that of humans.’

      Really? So if it comes down to a choice of me saving you from drowning or a cat, I should think of the cat as being just as worthy of protection as you – and rescue the cat first? Or if it comes down to a matter of feeding my dog to your starving children or your children to my starving dog – it’s basically all the same?

      People who are incapable of common sense or rational thought – AND who lack all humor AND who can’t put Dr Greger’s comments into the context of his extraordinarily humanitarian character – just should not comment. Really, do you destroy EVERY situation you are in with small-mindedness?

      Why am I asking? You clearly can’t see yourself as others see you. What a kill-joy.

    3. Greger was being sarcastic. Anyone with a sense of humour would catch that. And while I do not want to see any animals suffering needlessly, we can’t always tak in hushed tones about the reality. A human life is definitely worth more than an animal life, but suffering should be prevented for both.

    1. Lorraine

      Yes, according to this study below. In fact it might be an even bigger problem in Australia than in the US

      ‘ Using similar techniques to study 96 Australian women, we report here detection of retrotranscribed BLV DNA in breast tissue of 40/50(80%) of women with breast cancer versus 19/46(41%) of women with no history of breast cancer, indicating an age-adjusted odds ratio and confidence interval of 4.72(1.71–13.05). These results corroborate the findings of the previous study of US women with an even higher odds ratio for the Australian population.;

  4. In Australia we are now seeing this new milk treatment system (madebycow) as an alternative to pasteurization, it supposedly removes the pathogens without heat so is meant to taste better and has a much longer fridge life. Would be interested to find out what gets filtered and what doesn’t… just haven’t warmed to using rice or almond milk in coffee.

    1. I live in Queensland and oatmilk has worked well in my tea/coffee for years although I mostly drink them black now.

      the impression I have is that the new process only kills bacteria …. not viruses. So BLV might be an issue.

      1. I like oat milk in my coffee.

        I gave up coffee for over a year because I didn’t like the other plant milk, but oat is similar enough to milk that I enjoy coffee again.

        1. I am going to try to make my own oat milk.

          I found some with just oats soaked for 15 minutes, then blend with water. Then, strain.

          One added a date.

          One added vanilla and maple syrup.

          One of the people said that putting less water in makes it close to whole milk and they said that you can pour it into icecube trays and take a few out and blend them with smoothies or nice cream or put them in your very hot coffee.

          I also have been looking at making my own hummus. I don’t know if you can do it with boxed beans. I think I would need to get canned.

  5. My mom was a farmers daughter and they had milking cows also. She was one of 9 children and 2nd to the youngest. She died at the age of 57 of Leukemia and her father died at age 57 of lymphoma.

    Interestingly enough, we had a cat that died of leukemia about 15 years before my mother died of leukemia.

    It is intriguing how “Chimpanzees Bois and Roger didn’t develop detectable antibodies either, but died from BLV.”

    1. It’s called HUMOR. Understating something that is quite serious is a form of humor. You know, like, ‘Eating a pint of lard a day would be fine, if it weren’t for that pesky heart disease.’

      Over-sensitive Americans! Sheesh.

  6. Large animal veterinarians

    Funny: veterinarians that are also large animals. Large animals that are vegetarians.

    If you just hyphenate it (large-animal), joining two words into one, you get a compound adjective and the veterinarians go from being large animals themselves to being veterinarians who work with large animals.

    Meanwhile, I enjoyed having a Far-Side moment there (cows in lab coats; horses with stethoscopes),

  7. I decided to be dairy free due to all the controversy surrounding all dairy products. We don’t have to drink milk or eat cheese and yogurt, that is a choice we all make everyday. Watch what you eat. You should also know about oxidative stress and how we all have it naturally and the havoc it causes to our bodies.

    Check it out, oxidative stress. It’s what ages us and causes hundreds of illnesses and diseases. Dr. Greger, please do an article about Oxidative Stress.

    1. ‘Good for you giving up the milk products! You asked about Oxidative Stress and you’ll be glad to know Dr, Greger has produced not one but 127 videos mentioning this important topic. Why not go to the topic page and you can then check out ones you might be esp interested in. The first one listed you may fnd especially helpful:
      Hope this helps.

    1. Can’t think why there would be any difference ………….

      ‘Most BLV transmission is horizontal. Close contact between BLV-negative and BLV-positive cattle is thought to be a risk factor. Many common farm practices have been implicated in viral transmission, including tattooing, dehorning, rectal palpation, injections, and blood collection. Vectors such as tabanids and other large biting flies also may transmit the virus. Vertical transmission may occur transplacentally from an infected dam to the fetus, intrapartum by contact with infected blood, or postpartum from the dam to the calf through ingestion of infected colostrum. Any material that is blood contaminated or lymphocyte rich has the potential to infect animals with BLV.’

    2. Hi Sherri, thanks for your question. I researched it and Bovine Leukemia Virus (BLV) could happen in any cattle farm. So below is a description of how organic farm will deal with it.

      Bovine leukemia is another contagious viral disease of cattle also known as bovine leukosis or lymphosarcoma. BLV is spread among cows by blood contact. Multiple use needles and rectal sleeves, dehorning equipment, and biting flies can all spread this disease. Dams can also spread it to calves in colostrum and milk. Many cattle in the US are infected with BLV, but only a small percentage (less than 5%) develop cancer of the lymph nodes (lymphosarcoma). Finding lymphosarcoma will result in the carcass being condemned at slaughter.

      Best Management Practices for BLV

      Identify and remove positive cattle by blood testing.
      Prevent the further spread in the herd.
      Use single-use needles.
      Change rectal sleeves between palpations.
      Sanitize dehorning instruments between animals or use butane or electric dehorners.
      Control flies.

    1. Sounds like you just understood things right away, Dr. Connie.

      I did have a friend in college who was anti-milk and I just remember the one sentence that all animals except for humans are weaned off of milk when they are young.

      It is interesting that we are weaned off of mother’s milk, but someone decided to keep drinking it and it obviously became popular.

      I accidentally had dairy in two forms today. My brother made a Boca Burger for me, but he always gets confused about which person who eats Boca burgers orders it with cheese. Also, my in-law’s sister brought strawberries with a milk chocolate dip.

      I had bought strawberries this summer but never ate any and it was a goal, so I figured that chocolate would be a good way of succeeding.

      I already felt sick after the cheese and I mean that literally. I used to eat cheese every single meal and a lot of milk and now just half of a piece of cheese was so sickening.

      Everybody liked the vegan dish I brought, and I was happy about that.

      But I really still feel sick.

      My gut microbiome is saying “Don’t ever do that again.”

  8. Mastering Diabetes has a biog on C-Peptide levels and diagnoses of which type diabetes and on the page they said sentences like:

    If your level is above 4 you have a 95% chance of reversing it with diet.

    If your levels are between 2 and 4, there is a 50% chance of reversing it with diet.

    Under 2, the chance of reversing it with diet is only 5%.

    Do we know these numbers from a study?

    1. I also want to know if there is a study with Type 1 Diabetics and a high carb diet.

      They seem to be lowering their numbers.

      I don’t understand the mechanism.

      I do understand it for T2D, but why would going high carb help T!D?

      Does that mean it is something other than the Beta Cells?

      I do get that people get insulin resistance.

      Maybe I just am not understanding is that what happens?

      They can no longer make their own insulin and also become resistant to insulin or something?

      My friend who had the worst labs her doctor has ever seen is already balking conceptually at low fat. She was Gundry, so I didn’t understand that she gave up all Gundry’s foods and maybe ended up Keto or something.

      She is more afraid of not eating fat than she has been afraid of having Diabetes and not having it controlled.

      She is more afraid of not eating fat than she is excited that there might be a dietary way of reversing her Diabetes.

      I know that she is probably already all the way over to the point of seeing all of the plant foods and anti-nutrients. Blocking all of ther vitamins and minerals, which she is taking in the form of a lot of supplements.

      I might be the one with the messed up brain, but we all have analyzed the same data and I can’t even understand that their logic train went down the tracks it went down.

      She is an environmental scientist and has taken all of the science classes and I am just plain fascinated that I ended up with the opposite logic of everybody else.

  9. Why is the general public not being warned about BLV? Studies before and since have proven BLV migrates successfully into human tissue and can and does cause breast cancer. This issue has been on the medical radar for decades without the public hearing a whisper about it.

    In the meantime, countless women have died as a result. We can’t point our finger and name a name but the evidence is conclusive enough that the public should be given the option of making an informed choice rather than no choice.

    It has also been proven that BLV can migrate from cow to human to human offspring. That is happening. That is adding BLV to human genetics.

    This is a serious ethical question.

    Or am I missing something?

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