Have Millions of Americans Been Infected with a Cow Cancer Virus?

[Guest guest]

Have Millions of Americans Been Infected with a Cow Cancer Virus?

by Michael Greger, M.D.

January 9, 2004

 

Lost in the recent media flurry over Mad Cow disease, a provocative

study was released in the latest issue of AIDS Research and Human

Retroviruses.[1] Researchers at the University of California,

Berkeley found that a significant proportion of the American public

may be harboring antibodies to Bovine Leukemia Virus, which they may

have been exposed to through the consumption of beef or dairy

products.

 

Bovine Leukemia Virus (BLV) is a retrovirus that causes leukemia in

cattle. BLV infected cells (lymphocyets) circulate through the blood

of cattle and are present in both beef and milk.[2] As soon as BLV

was isolated in 1969 there were efforts to determine whether humans

were infected with the virus. Using the best tests available at the

time, researchers weren't able to detect antibodies to the virus in

the bloodstream of any human tested and so the USDA had concluded

that, " BLV is not transmissible to humans. " [3]

 

Compared to modern testing techniques, though, the tests they were

using in the 1970's were extremely insensitive. Realizing that back

then, researchers were even missing up to 70% of the positive bovine

cases,[4] Dr. Gertrude Case Buehring anf collegues at the University

of California School of Public Health in Berkeley wondered whether

the newer, more advanced testing methods would be able to detect

antibodies against BLV in human blood after all. So she took blood

samples from 257 people, mostly women, and tested them. Late last

month her results were published.

 

The study was designed to see if any humans at all had antibodies to

BLV. Dr. Buehring's group found antibodies reactive specifically

against BLV in 191 out of the 257 people studied. An amazing 74% of

the human subjects tested positive. Extrapolating this finding to the

general population, hundreds of millions of Americans may have been

similarly exposed to Bovine Leukemia Virus.

 

How did these people get exposed to this cattle virus? Less than 10%

had any direct contact with live bovines. Therefore, the most likely

explanation was due to their direct contact with dead ones (through

beef) or through live cow secretions (dairy products).

 

What exactly does it mean that people have antibodies against the

virus? Typically, the presence of antibodies to a particular virus

indicates either past or present infection with that virus. Dr.

Buehring concedes, though, that the presence of antibodies may just

be an immune response to consuming dead virus, killed by the

sufficient cooking or pasteurization of infected meat or milk . At

this point we don't have enough data to distinguish between the two

possibilities--active human infection from Bovine Leukemia Virus in

unpasteurized milk or undercooked meat, or merely exposure to killed

BLV.

 

If people can acquire active BLV infections, what consequences might

that have for their health? Public health advocates often point to a

study done 30 years ago in which 6 baby chimpanzees were fed

unpasteurized milk from BLV infected cows. The two infant chimps fed

the most infected milk were dead within a year of leukemia.[5]

 

Of course just because other primates become infected and die of

leukemia drinking infected milk, this doesn't mean that humans will.

Unfortunately, studies on human cell lines shows that indeed human

cells can also become infected with the BLV virus.[6] This still

doesn't necessarily mean that BLV can cause human disease, though.

Researchers needed to start studying human populations to see if they

could detect any association between BLV and human cancer rates.

 

Researchers found a disturbing trend. They found that geographically,

the areas of highest cattle BLV infection did indeed seem to have

significantly higher human leukemia rates. For example, in a study in

Iowa, the counties reporting the highest rates of cattle BLV

infection seemed to also have the highest rates of human acute

lymphoid leukemia (ALL), which typically strikes children.[7] Other

studies have found that milk consumption, for example, was associated

with the development of malignant lymphomas.[8]

 

BLV currently infects the majority of dairy and beef herds in the

United States and Canada.[9] In fact, an estimated 89% of the dairy

herds in the U.S. harbor infected animals.[10] Europe, on the other

hand, has very few infected animals.[11] This may be, in part,

because some of the ways in which young calves are treated in this

country have been deemed too cruel and banned in Europe.[12]

Instruments used in these procedures in the U.S.--ear taggers, nose

tongs, hoof knives, tattoo pliers, the needles on hormone implant

guns--may be inadequately sterilized and therefore may spread the

blood-borne virus.

 

Take, for example, dehorning. The saws and gougers used in dehorning

young calves cause so much bleeding and are so hard to clean that

they are particularly likely to drive potentially infected blood into

the next animal in line.[13] Dehorning is done in part to minimize

injuries to handlers and to reduce bruising during transport. To

minimize the risk of transmission of blood-borne pathogens like BLV,

the industry is moving away from gougers and more towards red-hot

electric irons or caustic paste to burn off the horn button.[14]

 

A modern Dairy Management textbook explains the use of the electric

iron: " lie the calf on its side and put your knee on the neck... The

dehorner has to be left on the button for approximately 5-20 seconds.

The time will seem longer, because of the combined unpleasantness of

burning hair and a struggling calf...dehorning may be complete...

when you hear a squeaking sound as the dehorner is twisted. It is the

sound of the dehorner tip rubbing against the bone of the skull. " [15]

 

Surgical castration--in which the lower third of the calf's scrotum

is cut off and the testicles are grabbed and literally just ripped

out--is another opportunity for blood-stained instruments to spread

infection. Both dehorning and castration are done in calves just 2-3

weeks old without any anesthetic.[16] The USDA notes that although

" Animal welfarists criticize the failure to administer anesthetics...

not using anesthetics for those relatively simple procedures greatly

reduces the complications caused by anesthetics.... " [17]

 

Other examples of practices that can spread BLV infection--done to

modify the animal to fit the system, rather than adapt the system to

accommodate the animal--are tail docking, which reduces the " chance

of the farmer getting swatted in the face, " [18] and " extra " teat

removal to " improve udder appearance. " [19 ]

 

Tail docking is becoming more widely accepted by dairy farmers.

Although one dairy textbook notes that " Some people object to the

docking of tails for humane reasons. In fact, the practice of docking

tails is banned in Great Britain. Others see no difference between

docking cattle compared to docking the tails of pigs and sheep or the

dehorning of cattle. " [20]

 

Removing " extra " teats is another unnecessary procedure that can

expose calves to infection. Up to half of all female calves are born

with " extra " teats on their udders. Dairy practitioners are taught

that " Extra teats should be removed for cosmetic reasons... " [21] The

Holstein Foundation explains " Extra teats on an udder are

unsightly... " The " extra " teats may also interfere with proper

placement of the milking machinery.[22]

 

A Dairy textbook explains the procedure: " extra teats detract from an

udder's general appearance. Grasp the teat between your thumb and

forefinger. Even in small calves, the nerve supply to their teats are

well developed. Make sure the calf is well restrained before you

proceed. Pull the teat outwards and take a generous bite with the

scissors. " [23] Slicing these nipples off of young calves is also done

without anesthetic.[24]

 

By continuing these unnecessary practices, we may be increase the

risk of spreading this diease throughout the U.S. cattle herd and by

extension, into the human population. The December study in AIDS

Research and Human Retroviruses concludes, " The long-held assumption

that BLV is not a public health hazard was based on the failure of

experiments in the 1970s to detect human antibodies to BLV. That

assumption is no longer tenable in view of our demonstration of

humans seropositive for BLV-reactive antibodies. " [25]

 

 

The preceding was excerpted from Dr. Greger's January 2004

<http://www.veganmd.org/newsletters.html>Newsletter. To to

his free once-a-month email newsletter send a blank email to:

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Anyone who missed any previous issues of my monthly newsletter are

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Michael Greger, M.D., has been the Chief BSE Investigator for Farm

Sanctuary since 1993 and the Mad Cow Coordinator for the Organic

Consumers Association since 2001. Dr. Greger has debated the National

Cattlemen's Beef Association before the FDA and was invited as an

expert witness at the infamous Oprah Winfrey " meat defamation " trial.

He has contributed to many books and articles on the subject,

continues to lecture extensively, and currently runs the Mad Cow

disease website http://www.organicconsumers.org/madcow.htm. Dr.

Greger is a graduate of the Cornell University School of Agriculture

and the Tufts University School of Medicine. He can be reached for

media inquiries at (206) 312-8640 or mhg1.

 

 

REFERENCES:

(Full text of specific articles available by emailing

article-request)

1 AIDS Research and Human Retroviruses 19(2003):1105.

2 Science 213(1981):1014.

3 http://www.aphis.usad.gov/vs/ceah/cahm/d96blv.htm

4 Journal of Virology Methods 104(2002):33.

5 Cancer Research 34(1974):2745

6 Cancer Research 36(1976):4152.

7 American Journal of Epidemiology 112(1980):80.

8 British Journal of Cancer 61(1990):454.

9 Veterinary Research 25(1994):521.

10 Working with Dairy Cattle.

http://www.holsteinfoundation.org/pdffile/f1325.pdf

11 DairyBiz February 1999. http://www.moomilk.com/archive/a_health_29.htm

12 http://www.wspa.org.uk/data/201202_121055_FAW_-_Tokyo_Symposium.pdf

13 http://nyschap.vet.cornell.edu/module/leukosis/section1/BLV%20brochure.pdf

14 http://www.moomilk.com/archive/a_health_29.htm

15 Practical Techniques for Dairy Farmers. 3rd Ed. University of

Minnesota, 2000.

http://www.ansci.umn.edu/practical-techniques/book.htm

16 Practical Techniques for Dairy Farmers. 3rd Ed. University of

Minnesota, 2000.

http://www.ansci.umn.edu/practical-techniques/book.htm

17 Arave, CW and JL Albright. " Animal Welfare Issues: Dairy. " AWIC

Newsletter 9(1998):3-10. The Animal Welfare Information Center is

part of the USDA Agriculture Research Service.

18 Practical Techniques for Dairy Farmers. 3rd Ed. University of

Minnesota, 2000.

http://www.ansci.umn.edu/practical-techniques/book.htm

19 Dairy Connection December 1999.

http://www.ag.ndsu.nodak.edu/aginfo/dairy/dairyext/dc9-4.htm

20 Practical Techniques for Dairy Farmers. 3rd Ed. University of

Minnesota, 2000.

http://www.ansci.umn.edu/practical-techniques/book.htm

21 Management of Dairy Heifers.

http://www.das.psu.edu/dcn/CALFMGT/pdf/385b.pdf.

22 Dairy Connection December 1999.

http://www.ag.ndsu.nodak.edu/aginfo/dairy/dairyext/dc9-4.htm

23 Practical Techniques for Dairy Farmers. 3rd Ed. University of

Minnesota, 2000.

http://www.ansci.umn.edu/practical-techniques/book.htm

24 Working with Dairy Cattle.

http://www.holsteinfoundation.org/pdffile/f1325.pdf

25 AIDS Research and Human Retroviruses 19(2003):1105.

 

 

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