Cow virus suspected in human breast cancer

A cancer-causing virus infects almost all cattle operations in the United States. Why am I writing about this? Because this cow virus may cause breast cancer in humans.

This virus infects 39 percent of beef cattle herds and 94 percent of dairy herds.[1],[2]

Called by a variety of similar names–bovine leukemia virus, bovine leukemia/lymphoma virus, bovine leukosis virus–or just BLV for short, this virus definitely causes cancer in cows. The suspicion that BLV is a cause of some human breast cancers has been around for 40 years or so, and the link hasn’t been completely proven yet. But many technologically advanced countries: Australia, Singapore, and some European countries have decided any such risk deserves to be taken seriously. 

These countries have taken drastic measures. They’ve  culled all infected animals. They’ve gotten rid of the virus. 

In the United States, however, culling infected animals is considered unnecessary. In fact, testing for BLV is considered unnecessary. The reason given is not because the health issues are still in question. I want to point out that they are in question, and much research is still needed.

But testing cattle for the virus doesn’t improve the economic bottom line. This reasoning says that because infected cattle don’t develop cancer until an older age, and because most are slaughtered for meat before reaching that age, why spend money to test them?

Only about 5% of cattle do develop cancer from BLV. This loss is economically acceptable, however, compared to the direct costs of testing and culling infected animals. I also wondered about the indirect costs of testing. The political and economic costs of testing, which would of course involve admitting to consumers that there may be a problem with the safety of United States cattle herd, could indeed be costly. That’s one way of thinking about it. 

However, for farmers who want to sell organic products to health-conscious consumers, offering products from BLV-free animals would, of course, be lucrative.

I expected organic or organic plus A2 dairies to be aware of this issue and to be approaching it more proactively.  I wrote to one very high quality local organic dairy asking them to confirm that they tested for this virus, expecting the answer to be yes.

But the answer was not an enthusiastic “Yes!” The answer was more shocking than a simple “No, we don’t test.”

The answer was, “What’s BLV?” They’d never even heard of it.

At least one dairy newsletter has discussed the BLV problem. Take a look at this article by a professor and veterinarian at the University of Pennsylvania. (Suggestion: read the summary first. The shock was enough to propel me through the entire article.)

The article warns dairies that because of the possible threat to human health, testing for BLV and culling herds may become mandatory at some point soon. Getting a head start by testing and culling infected animals might be prudent for forward-thinking dairies.

Translation: testing and removing infected animals could indeed be good for the bottom line—if consumers demand it.

What to do for now: 

  • Boil or at least pasteurize your milk. Pasteurization at 145 degrees Fahrenheit for 30 minutes inactivates the virus.
  • Eat cheese from pasteurized milk. (Read the label.)
  • Cook beef well.
  • Email your dairy or beef farmers and ask if they test for BLV.

For further reading:

A balanced look at the US approach to BLV:

BLV advice for proactive farmers, from land grant university extension programs:

Medical research article about viruses possibly related to human breast cancer:

[1] LaDronka RM, Ainsworth S, Wilkins MJ, Norby B, Byrem TM, Bartlett PC. Prevalence of Bovine Leukemia Virus Antibodies in US Dairy Cattle. Vet Med Int. 2018;2018:5831278. Published 2018 Nov 11. doi:10.1155/2018/5831278