"The Role of Bovine Leukemia Virus in Breast Cancer"
Up to 20% of all cancers are linked to infections,
particularly viruses,
and the list of potentially carcinogenic infectious agents is growing.
It could be great if we found a virus
that contributed to breast cancer risk,
because then we might have new ways
to prevent and treat it.
Currently, the dietary link between meat and dairy
and breast cancer is considered a saturated fat effect,
but there is a cancer- causing cow virus
that infects the mammary gland cells of cows.
Infectious virus is then released
into the milk supply,
and since most U.S. dairy herds are infected,
scientists figured Americans are often exposed
to this bovine leukemia virus,
but we didn’t have proof until 2003,
34 years after the virus was first identified.
Early on, our best available tests failed
to find antibodies to the virus in human blood.
When our immune system is exposed to a virus
it creates antibodies to attack it.
No antibodies, no exposure
so this led to the prevailing opinion
that this virus poses no public health hazard.
Those tests were state of the art at the time,
but extremely insensitive
compared to more modern techniques,
so researchers decided to re-examine the issue
now that we had better tests.
So they took blood from about 250 people
just to answer the question,
"Do any humans have antibodies to bovine leukemia virus?"
And 191 of them did, 74%....
Not that we should be surprised.
by then nearly 90% of American dairy herds were infected
and in the latest national survey,
100% of the big factory farms were infected
when you test the milk coming out of those operations.
So why isn’t there an epidemic of udder cancer out there?
See, dairy cattle are hamburgered so young
that there’s not a lot of time
for them to develop gross tumors.
And that’s how most women may be getting infected.
Although pasteurization should knock out the virus,
who hasn’t eaten a pink-in-the-middle burger
at some point in their life?
The bottomline is that the long-held assumption
that bovine leukemia virus is not a public health hazard
is no longer tenable.
This whole field of investigation needs to be reopened,
with the next step determining
whether humans are actively, actually infected.
The presence of antibodies is generally interpreted
as an indicator of past or present infection,
but theoretically maybe we just made antibodies
to dead virus we ate, virus that had been killed
by cooking or pasteurization.
Just because three-quarters of us had been exposed,
doesn’t mean we were actively infected with the virus.
To prove that we’d actually have to find the retrovirus
actively stitched into our own DNA.
Well look, millions of women have gotten breast surgery
why not just look at that tissue?
Researchers did and in 2014 published their findings
in the CDC’s emerging infectious diseases journal,
and 44% of samples tested positive,
proving for the first time that humans can be infected
with bovine leukemia virus.
The final step, then is to determine
if the virus is actually contributing to disease.
In other words, are the bovine leukemia viruses we’re finding
in human breast tissue cancer-causing
or just harmless passengers?
One way to figure that out is to see if the virus
is more often present in those with breast cancer,
but no one had ever looked for the virus
in breast tissue from cancer victims...
until now.
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.